Waves
A collection of over 250 �physics teaching ideas
Ideas compiled by Simon Poliakoff as part of an Ogden Trust Senior Teacher Fellowship. �Thank you to the Ogden Trust for giving me the time to do this! �This work is licensed under CC BY-NC-SA 4.0
Whilst I have tried to identify significant hazards in demonstrations and practicals you should complete your own risk assessments before using them. Click here to leave feedback.
Screen shot used with kind permission of Farid Minawi
Screen shot used with permission from Javalab What colour does it look?: https://javalab.org/en/color_en/
Wave diffraction Oualida lagoon, south of Casablanca 16-06-2023. Google Earth image use permitted for non-commercial purposes.
Quick links for different sub topics
Wave equation and calculations
Sound production, propagation and measuring the speed of sound
Describing sounds, oscilloscope traces
Key to Icons
Icon | Meaning |
| Simulation/Interactive |
| Demonstration |
| Student Practical |
| Discussion |
| Question |
| Next time Question |
| T&L idea |
| Model/Analogy |
Icon | Meaning |
| Video |
| Story |
| Calculation |
| Reading task |
| Written task |
| Song/Music |
| Diverse |
| Joke |
| Careers |
| Link to everyday life |
Icon | Meaning |
| Easy to implement. quick and using fairly standard resources |
| Medium difficulty to implement may require cheap new resources and or a little tinkering |
| Hard to implement may require more expensive resources and/or tinkering |
| Key for teaching |
| Quick |
| Wow factor/hook |
Which key stage is it good for?
Key stage 3 Age 11-14
GCSE� Age 14-16
A-Level
Age 16-18
Thanks to the following for their help and contributions:
Individuals
Organisations
The Ogden Trust �for funding my time
And for their ideas, advice or giving permission for screenshots or use of extracts of their resources:
BEST - Best Evidence Science Teaching
Engineering UK �Phyphox�Science on Stage Ireland�Academo.org �earthlearningidea.com �Lascells�Perimeter Institute
Dan Jones�Dan Russell�Alom Shaha�Tom Walsh�Lewis Matheson �David Ridings�Maureen Wade�Farid Minawi�Rhett Allain�Jed Marshall�Andrew Fusek Peters�Xmdemo�Dr. Boyd F. Edwards,�Daniel Wilson�Manuel Joffre�Henry Hammond
And all the other physics teachers I have worked with and learnt from either in person or online.
Bruce Yeany�Michael Freeman�Callum Farnsworth�Shannon Mooney�Jack Friedlander �Wild Haired Science Teacher�Helen Reynolds�Joe Cossette�Matt Prichard�Richard Brock�Richard Epworth�Nick Mitchener�Keith Miller�Fabrizio Logiurato�Ronan McDonald�Paul Williamson�Alex Johnston
Waves Basic Ideas
Source, medium, receiver model
Description:
A useful structure for discussing all waves is the source, medium and receiver model. The source (e.g. loudspeaker) produces the wave, the wave travels through a medium (e.g. the air) until it is absorbed by the receiver (e.g. your ear).
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Source
Receiver
Medium
Introduce waves with a video of large water wave
Description:
To provide a link to everyday life and a starting point to the waves topic a video clip of some water waves is useful.
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Longitudinal and Transverse waves on a slinky
Description:
A long slinky spring provides a straightforward way to demonstrate the difference between transverse and longitudinal waves. Attaching a white sticker or similar part way along the slinky can make it easier for students to see how the turn of the slinky is moving compared to the direction of energy transfer.
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Transverse waves on a rope
Description:
Transverse waves can easily be demonstrated on a piece of rope held between two people. The video discusses how you can vary the tension to show how the speed of the wave changes but you can also use it to simply show a transverse wave and reflection of the wave from the far end.
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Slow moving wave on a rope
Description:
This fun demonstration from Bruce Yeany involves using a motor to make a rope loop move round at almost the same speed that a wave would travel along it. You then send a wave in the opposite direction and it appears to move very slowly.
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Student role play of longitudinal and transverse waves
Description:
A row of 6+ students stand all facing the same way with linked arms. They can role play a longitudinal wave by stepping sideways into the next student and back again. They can model a transverse wave by stepping forwards and back again.
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Images used courtesy of the IOP see link below for the article on IOP spark
Jelly Baby Wave Machine
Description:
A lovely demonstration of a waves transferring energy rather than matter. After showing a wave ask students to point in the direction the wave travels. Then ask them to choose a particular jelly baby to watch and then to point in the direction the jelly baby moves. Then ask what travels along the wave since it isn’t the jelly babies - it is of course energy.
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Image or video
Animations of Longitudinal and Transverse Waves
Description:
A range of useful animations and interactives for showing the differences between longitudinal and transverse waves
Phet wave on a string (transverse)
Lovely simulation of longitudinal and transverse waves
Longitudinal and Transverse Wave Basics
Falstad ripple tank simulation
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Waves key terms glossary and writing comparisons
Description:
There are a lot of key terms in the waves topic. It is helpful to provide students with a glossary which they can fill in (completed one here).
Then get students to practice writing comparisons using the key terms on e.g. mini whiteboards. These slides have some examples in.
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Interactives for comparing waves
Description:
These two animations from Michael Freeman’s website afreeparticle.com are excellent for getting students to compare waves. The first one allows you to adjust the properties of two different waves and the second one students can use to try and decide which wave has the greater amplitude, frequency, wavelength and speed.
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Screenshot from a free particle by michael freeman is licensed under CC BY-NC-SA 4.0
Role Model Hertha Ayrton
Description:
Ayrton was an engineer and mathematician, physicist, inventor as well as a suffragette. She worked around 1900 studying the effect of water waves on small particles and sand.
She later designed a hand held fan to remove poisonous gases from trenches in the First World War.
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Image or video
A model to understand the link between �waves and wavefronts
Description:
Students can find it difficult to understand the link between the wave representation and a wavefront representation of waves. This simple model shared by Jed Marshall can be helpful. It is constructed from pieces of OHP transparency and cocktail sticks or barbecue skewers.
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Image:Jed Marshall
Animations to show difference between �displacement-distance and displacement-time graphs
Description:
Understanding the difference between a displacement-distance graph which is like a photograph of the wave at a point in time and a displacement-time graph which shows the displacement of a particular point as time passes can be difficult for students.
Dan Russell's animated gif on the right or this geogebra simulation are helpful for showing this.
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Demonstrations with a basic ripple tank
Description:
More basic ripple tanks use an unbalanced motor attached to a bar to create the ripples. The frequency of the waves is controlled by varying the voltage connected to the motor. In my experience you can get better results by replacing the light they came with by a LED strip torch such as NEBO big larry 2 about a 1m up on a tall clamp stand with the LED strip parallel to the wavefronts. As well as using a rheostat to finely control the voltage connected to the motor.
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Demonstrations with modern ripple tanks
Description:
Various science suppliers make a more modern ripple tank designs which use a vibration generator and signal generator together with a built in strobe to produce more stable ripple patterns. (Before buying check if you need an external signal generator or if it is built into the ripple tank)
Easy to setup and use if you have one or can afford to buy one
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Waves Revision Song
Description:
An entertainment song to play when revising the waves topic at GCSE.
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Image or video
Waves Equation and Calculations
Introducing T=1/f with simple examples
Description:
Rather than giving students the equation for T = 1/f use a series of question to get them to spot the relationship:
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Simple PhET investigation to introduce the wave equation �and key terms of wavelength, amplitude and frequency
Description:
The PhET waves on a string simulation is an excellent way to introduce the key terms: wavelength, amplitude and frequency and the wave equation.
https://www.pheteffect.com/waves by Callum Farnsworth has helpful resources to structure this with the wave properties simple investigation.
Works best with a device per student but can also be used for class discussion on the board.
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Simulation by PhET Interactive Simulations, University of Colorado Boulder (https://phet.colorado.edu), licensed under CC-BY-4.0.
Introducing v=fλ using speed = distance/time
Description:
Use a series of questions to get students to deduce the wave equation and see that it is just an application of:�speed = distance / time.
Either use the questions on the right to deduce the relationship directly or use distance / time as wavelength/time period and f=1/T
Nice follow up BEST slides from slide 19 here. �BEST Teacher notes and worksheet here.
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Measuring speed of a wave pulse in a tray
Description:
A wave pulse is created by lifting one end of a rectangular tray by a few cm with about 1 cm of water in the bottom, waiting for the water to settle and then dropping the tray.
The time for the wave pulse to travel 1,2,3,4,5,6 times across the tray can be recorded using a stopwatch.��BEST slides to introduce the activity
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BEST questions for introducing measuring wave speed on ripple tank
Description:
Slide 35 onwards in these BEST slides has some good questions for introducing measuring wave speed with a ripple tank. Teacher notes and student worksheets here.
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Ripple tank image: © University of York Science Education Group. Distributed under a Creative Commons Attribution-NonCommercial (CC BY-NC) license.
Measuring speed of waves in a ripple tank (old/ traditional ripple tank)
Description:
On an older traditional design of ripple tank it is likely to be necessary to video the waves together with a stopwatch (or taking the time from the video frames) to determine the frequency. The wavelength can be determined by counting the number of wavelengths between two markers. Then the wave equation is used to calculate the wave speed.
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Measuring speed of waves in a ripple tank (new style ripple tank)
Description:
Some schools have a more modern ripple tank which runs from a signal generator with built in strobe feature (or even with the signal generator built in). This makes it easier to get the frequency directly from the signal generator or using a multimeter set to measure frequency.
The video goes through the steps to measure the wavelength
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Measuring speed of waves on a string
Description:
GCSE required practical which uses a vibration generator and signal generator to create a stationary wave on the string. The frequency can be measured using a built in frequency meter on a signal generator or the frequency setting on a multimeter. Each vibrating loop on the stationary/standing wave created represents half a wavelength and can be measured using a meter ruler.
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Image or video
Practicing finding the wavelength from a wave on string
Description:
Students often find it difficult to work out the wavelength of the waves from a wave on a string required practical (see the previous slide). �
You can practice this using the following simulation.
Frequency = 45Hz,
Linear density = 0.777 x 10-3 kg/m
and Tension =100N
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Screenshot from ophysics.com. �Used on basis of general permission notice on the website:
Stationary/standing wave on a string with an electric toothbrush
Description:
If you don’t have a vibration generator then you can create stationary/standing waves on a string using an electric toothbrush with the head removed. Rather than adjusting the length or frequency it is easiest if you use a piece of thin elastic and adjust the tension in the elastic until a clear stationary/standing wave is formed. Thanks to Keith Gibbs for sharing this idea.
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Sound production, propagation and measuring speed of sound
Polystyrene cup and slinky star wars sound effects
Description:
Putting a polystyrene cup in the end of a slinky and shaking it makes interesting sound effects. The increased surface area of the cup means the vibrations more efficiently produce sound waves.
You can extend to try different cups in the end of the slinky.
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Hex nut in a balloon
Description:
Swinging a hex nut round in a balloon create an interesting sound. Watching this in slowmo shows how the hex nut rotating causes the surface of the balloon to vibrate and produce a the sound.
You can hear the frequency change as you spin it faster and the nut rolls round faster.
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Dancing Sprinkles
Description:
Cling film is stretched over a bowl and held in place with a rubber band. Sound is produced (either with a loudspeaker as shown in the video or by hitting a spoon on a metal tray or similar). The sprinkles are observed vibrating.
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Loudspeaker and rice/polystyrene beads
Description:
A loudspeaker connected to a signal generator (or amplifier playing actual music) has rice or other light things on it which shows clearly how the loudspeaker is vibrating.
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Simple tuning fork demonstrations or practicals
Description:
Tuning forks can be used to show sound is produced by vibrations by touching the end into water, touching a tuning fork. They are also good to demonstrate that if you increase the size of the vibrating thing by touching the base of the tuning fork onto a board that the volume increases.
Avoid using with glass beakers as the tuning fork can shatter the glass.
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Candles in sound wave
Description:
Candles placed close to a loudspeaker driven by a signal generator can be seen to vibrate/oscillate in the sound wave.
Take it a stage further and synchronise the frequency of the signal generator and the frame rate of the phone/tablet camera to create a slow motion effect (see linked video)
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Image or video
Simple animations of sound wave travelling
Description:
Simple animations showing the propagation of a longitudinal sound wave through particles. Students can watch a highlighted particle in red to see that the particles oscillate parallel to the direction of energy transfer.
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This work by Dan Russell is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Models of how sound travels through the air
Description:
A nice model to show sound waves propagating through the air is to have a series of ping pong balls hanging on thin thread/string to represent . Then when the first ping pong ball is touched with a tuning fork you can see the vibration being passed on to the next one.
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Bell in bell jar
Description:
An electric bell is hung in a bell jar and when a vacuum pump is used to reduce the air pressure inside the volume of the bell decreases significantly.
Should be carried out with a safety screen incase the bell jar failed and imploded. If you have an old mobile phone you can use that instead of a bell.
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Dominoes speed of sound model/analogy
Description:
Dominoes are used as an analogy to show why sound travels faster in solids than liquids/gases. The pulse travels along the dominoes which are closer together (representing the solid) than those further apart (representing the liquid/gas).
Whilst the model appears good it ignores the role of bonding between the particles. Speed of sound in ice is nearly three times faster than water but ice is less dense than water. This can provide a talking point about the limitations of simple models.
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Listening to sound travelling through a solid
Description:
A metal coat hanger on string a piece of string which is held in contact with the ear and gently tapped against the side of the table produces an impressive bell like sound. This shows that the vibrations / sound waves are transmitted more efficiently through a solid than in air.
The video simulates the sound you hear by recording the sound with the string pressed against a phone microphone.
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Noisy neighbour videos
Description:
Noisy neighbour videos area fun way to introduce idea of measuring volume of sound. The video linked on the right about a role play flat set up in Singapore but there are lots of other examples that you can find easily.
Thanks to David Ridings for sharing the idea
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The decibel scale and measuring volume of sounds
Description:
A sound level meter or app on mobile phone can be used to measure the volume of sounds in dB. It is a logarithmic scale because the human ear can detect such a large range of volumes of sound.
It can be fun to challenge students one at a time to try and make the loudest sound.
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Image: Cirrus Research Plc CC BY-SA 3.0
Buzzer in box with sound insulation
Description:
A simple practical is to use a buzzer, alarm clock or phone sounding an alarm and wrap it in different materials inside a box to see which material is the most effective at insulating from sound. To make it quantitative you need a sound meter or data logger with sound level although you can use a phone or other device with a suitable app.
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Pipeline funk video
Description:
A lovely video of a saxophone playing a duet with the echo in a long pipeline.
Use the echo time to estimate the length of the pipeline or introduce that an echo is a reflection of sound or to get students discussing how to measure the speed of sound from an echo.
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Speed of sound echo method
Description:
Two wooden blocks are banged together and the time for the echo from the side of a building/cliff is measured. The distance to the wall is measured. This allows the speed of sound to be calculated. Can be increased in accuracy by playing back the video more slowly or banging in time with the echo to allow a longer time to be measured.
Thanks to Jack Friedlander for making this video with me some years ago.
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Speed of sound with millisecond timer
Description:
Two microphones are placed a known distance apart. A millisecond timer starts as a loud sound reaches the first microphone and stops as the sound reaches the second microphone. The phillip harris unilab kit includes a hammer and plate to make the sound.
Can place the microphones face down on the bench and measure the speed of sound in a solid.
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Speed of sound with oscilloscope and two microphones
Description:
Two microphones are placed about 1 m apart and connected to a dual sampling channel oscilloscope (picoscopes work well). A loud crack is made by banging two blocks of wood together near the first microphone. The time for the sound to travel between the two microphones is measured from the oscilloscope trace produced and then used to calculate the speed of sound.
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Estimating the distance to thunder
Description:
You can estimate the distance to thunder by assuming that the light has arrived instantly and so the delay between the thunder being heard and the lightning being seen is the time taken for the sound to travel. Which takes approximately 3 seconds per km or 5 seconds per mile.
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Describing sounds, �oscilloscope traces and applications
Key terms for describing sounds and sound waves
Description:
A sounds should be described as loud or quiet (linked to the amplitude of the sound wave or vibration) and as high or low pitched (linked to the frequency of the sound wave or vibration).
It is helpful to practice describing some sounds (ideally made with everyday instruments and objects) before introducing oscilloscope traces. A good idea to change the volume whilst keeping the pitch the same and vice versa.
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Image: © University of York Science Education Group. Distributed under a Creative Commons Attribution-NonCommercial (CC BY-NC) license.
Slink-o-scope
Description:
Students often find it difficult to understand why a sound wave which is longitudinal is represented on an oscilloscope trace by something which looks transverse. In fact the oscilloscope trace is more like a displacement-time graph so doesn’t actually give you any information about which type of wave it is. This simple demonstration uses a mechanical mechanism to turn longitudinal oscillations in a slinky into a displacement-time graph.
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Visualising longitudinal waves on a slinky
Description:
A piece of cardboard is attached to the middle of the slinky. A motion sensor (ultrasonic ranger) data logger is used to plot a displacement-time graph of the cardboard as longitudinal waves are sent along the slinky.
It clearly demonstrates that a displacement-time graph of a longitudinal wave looks like the shape of a transverse wave.
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Visualising longitudinal waves on a slinky
Further Guidance:
David Clark suggested the following sequence to introduce the demonstration:
If you have the technician support and enthusiasm you can also buy or build motors with an adjustable arm which can consistently produce a range of frequencies or amplitudes.
Displaying oscilloscope traces of sounds �using a signal generator and loudspeaker
Description:
You can quickly teach students to recognise the volume and pitch of a sound from an oscilloscope trace by using a signal generator connected to a loudspeaker and the oscilloscope.
Can also use a microphone to display live sounds (whistling produces a clear simple trace)
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Displaying oscilloscope traces of sounds �using an online oscilloscope or real oscilloscope
Description:
If you don’t have an oscilloscope and microphone then consider using this basic online oscilloscope simulation which you can either adjust the frequency of and AC signal generator or use live input from the microphone Virtual Oscilloscope | Academo.org - Free, interactive, education.
These BEST slides are useful for discussing how the waveform is create on the oscilloscope.
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Screen shot used with kind permission of academo.org
Whistling oscilloscope traces using phyphox
Description:
Using the audioscope from the free Phyphox app you can easily display oscilloscope traces of sounds. Whistling produces a very clear sine wave shape.
By adjusting the pitch and volume of the whistling you can easily show how the oscilloscope trace changes.
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Interpreting oscilloscope traces quiz
Description:
A mini white board quiz (click here for the slides) for students to describe the sound from an oscilloscope trace and explain their reasoning by referring to the amplitude and frequency of the wave.
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Music waves simulation
Description:
This simple simulation from the wild haired science teacher is nice to use when introducing oscilloscope traces. Students can click on a piano key and adjust the volume and the note is played as well as an oscilloscope like trace of the sine wave of that frequency being displayed.
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Time period vs wavelength misconception
Description:
Great care is needed to avoid students referring to wavelength when looking at a displacement-time graphs or oscilloscope traces. The gap from one peak to the next represents the time for one complete oscillation and NOT the wavelength.
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Time Period
Simulation of an oscilloscope
Description:
A very realistic simulation of an oscilloscope which can be connected to a signal generator or DC power supply.
Useful for teaching about how to adjust the time base and volts per division before using a real oscilloscope.
https://physics-zone.com/virtual-oscilloscope/
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Screen shot used with kind permission of Farid Minawi
Finding amplitude and frequency from an oscilloscope trace
Description:
Teaching how to use oscilloscopes and interpret traces is a key practical skill. These slides provide the steps for finding amplitude (peak potential difference) and frequency.
These are some editable step by step instructions for setting up and using an oscilloscope. Will need tweaking based on the oscilloscope you have.
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Ruler vibrating on edge of table
Description:
A ruler is held firmly on the edge of a table/lab bench with one hand and the other end plucked. The pitch of the sound produced is noted and then the length of ruler that is free to vibrate is reduced.
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Image or video
The straw oboe
Description:
A plastic straw is made into a simple reed instrument. Blowing through it produces a sound a bit like an oboe. You can use to see how the length affects the pitch.
Plastic straws work better than paper ones.
Thanks to Helen Reynolds for suggesting this activity.
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Image or video
Boomwhackers to demonstrate length and pitch
Description:
A nice practical activity for younger students to see the link between length and frequency is using Boomwhackers or other alternative percussion tubes. You can combine it with using the audio autocorrelation from the free phyphox app if you want to gather some quantitative data.
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Instrument Frequency Lab/Investigation
Description:
A simple investigation to see the relationship between frequency of sound produced and with different volumes of water added to a glass which is tapped with a fork. Can also be done for blowing across the top of a bottle.
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Whirling sound tube
Description:
Swinging the tube round produces a sound because of a stationary wave created in the tube. For younger students you can just use it as an interesting engagement for producing sound. For A-level students you can measure the frequency produced and see how it matches up to the frequency of the stationary wave based on the length of the tube.
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Image or video
Video introduction to the Ear
Description:
This video provides a nice simple introduction to how the ear works at a level suitable for secondary school physics.
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Image or video
Human hearing range demonstration
Description:
The frequency of a tone is slowly increased/decreased until students can no longer hear it. This allows them to find their own hearing range. You can either do this with a signal generator and loudspeaker (see video on the right) or using an online tone generator
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Mosquito alarm and ringtones
Description:
A mosquito alarm is a device designed to deter loitering by emitting a high pitched tone. Sometimes these can be chosen so that they only affect younger people who can typically hear higher frequencies than older adults.
Also became popular as ringtones that teachers and parents could not hear when people actually made phone calls on phones.
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Image public domain from: https://en.wikipedia.org/wiki/The_Mosquito#/media/File:Mosquito_Noise_Device.jpg
Sound Engineer Role Model - Eloise Whitmore
Description:
Eloise Whitmore is a sound engineer for radio and television. Her job is to record all speaking parts and acoustics and then add sound effects after. Eloise says that you need to make a world of sound to make people feel like they are actually there. She needs an understanding of frequencies to get the best sound and you need to have a good ear to pick out the sounds – and a pair of silent trainers so you can move around without being heard. Text used with permission from the OCR STEM contributors resource link below.
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Role Model - Orla Murphy
Description:
Orla Murphy was interested in STEM subjects and music at school so combined the two by doing a degree in Electronics with Music. She now works at Jaguar Land Rover as an audio engineer trying to make car stereos sound like you are in a concert hall. She positions microphones where a driver's ears would be and takes acoustic measurements of the sound system to optimise the frequency response by altering the software of the amplifier. Text used with permission from the OCR STEM contributors resource link below.
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How were these used before the invention of radar?
Description:
Without telling students what they are show a photograph of some sound mirrors and ask the students how they were used before the invention of radar.
The answers is to listen for the sound of approaching enemy aircraft. The parabolic shape reflects all the waves towards the focus and allows the planes to be heard when they were much further away than without the sound mirrors.
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Photo: Denge, Kent © Simon Poliakoff
Sound lens / Refraction of sound
Description:
A carbon dioxide filled balloon acts as a lens for sound because the speed of sound is lower in carbon dioxide than in air (because of the slower average speed of the carbon dioxide molecules).
It can be demonstrated using a microphone and oscilloscope as shown in the video or someone can hear it get louder when the balloon is inserted between them and the loudspeaker
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Image or video
Breaking a glass using resonance
Description:
A loudspeaker and signal generator tuned to the natural frequency of a glass can cause it to shatter. The linked video on the right shows it happening in super slowmo and you can see the glass oscillating and then the cracks propagating.
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Ultrasound and Echo Sounding
Simple ultrasound animations
Description:
Simple PowerPoint animations showing a pulse of ultrasound being emitted, partial reflections and detection with an oscilloscope. Scenarios include cracks in metal and change in density in tissue.
You can follow this up using some animations which link how this can then be extended to produce images using this IOP set of slides
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Steps for calculating distances using �ultrasound oscilloscope traces
Description:
These slides include suggested steps for a simple routine for interpreting oscilloscope traces and calculating distances.
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Echo sounding demonstration
Description:
A data logging motion sensor (ultrasonic ranger) mounted on a clamp stand and dynamics trolley is slowly scanned across a stack of tubs.
The data logged graph produced shows the shape of the stacked tubs.
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Image or video
Role Model - Diane Crawford
Description:
Dr Diane Crawford was a pioneer in using ultrasound for foetal-heart scanning. This involves analysing the reflections of high frequency sound waves that have been sent into the abdomen of a pregnant woman to build up a detailed image of the structure of the heart of the foetus. The techniques that Diane helped develop are now used around the world.
Text used with permission from the OCR STEM Contributors resource. Access the full resource below
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By Julan Shirwod Nueva - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=82677143
Mini Ultrasonic Levitator
Description:
You can buy these mini ultrasonic levitators for a few pounds from the usual online outlets. By measuring the distance between the floating bits of polystyrene you can deduce the wavelength and hence calculate the frequency of the ultrasound which can be cross checked by displaying it on an oscilloscope using a microscope. You can buy larger ones which are more impressive but cost rather more.
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Light - The basics
Modelling shadow formation with string
Description:
You can use pieces of string or wool to model how a shadow is formed. In the video an opaque ruler casts a shadow from an LED strip torch and the string is used to show where the edges of the shadow are expected to be.
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Demonstrating that light travels in straight lines
Description:
The path of a laser beam travelling through the air can be revealed using a fine powder, fine water spray or smoke spray.
Follow usual guidance for using a laser in school (less than 1 mW and ensure that the laser or reflections of the laser cannot enter anyone's eye)
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Natural examples of light travelling in straight lines
Description:
Natural examples of demonstrations of light travelling in straight lines such as this video clip showing light scattering from water droplets after a heavy rain shower in Madeira are a nice follow up to the demonstration with a laser.
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Identifying Luminous and Non-Luminous Sources
Description:
Students identify using mini white boards or electronic equivalent examples of luminous and non-luminous sources.
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Image or video
Transparent, Opaque and Translucent
Description:
Students classify materials as transparent, opaque or translucent. Good to start of working from photographs and using mini whiteboards and then give them some physical materials to sort.
Some things are hard to classify.
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Absorb, Transmit and Reflect with Infrared Camera
Description:
If you have an infrared (thermal imaging) camera. Then this series of five demonstrations are a fun way to get students writing explanations using the key terms absorb, transmit and reflect. Infrared is transmitted by thin black plastic but light is absorbed. Whereas glass transmits visible light but mostly absorbs
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Pinhole camera practical
Description:
This is a classic practical which is really engaging for students. If you have old fashioned carbon filament lamps they are ideal but if not other bulbs with a filament that you can tell which way up it is are perfect. Warn students that the carbon filament bulb will get hot and not to touch it.
Worksheet for drawing ray diagrams�Further BEST ideas and notes for the pinhole camera
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Modelling the pinhole camera with rayboxes
Description:
A ray box and two pieces of card are used by students to model the ray diagram to explain how a pinhole camera works. The students can then complete their own ray diagram. It works well to play the video to explain the idea before the students do the practical.
Useful BEST diagnostic question about the pinhole camera and notes.
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Drawing ray diagrams to explain seeing
Description:
Students assess (critique) a series of ray diagrams to explain seeing luminous and non-luminous objects before drawing their own.
Another related activity is to model this using wool which is described in this video.
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Light - Reflection
Investigating the law of reflection
Description:
Students use a plane mirror and a pre printed protractor to conduct a quick investigation of the law of reflection.
To get the expected result it is helpful to use the video to show the required setup and then use the mini whiteboard questions about identifying the mistakes in each of the photographs in these lesson slides.
If you want to avoid the pre printed protractor then this video shows the method and you can get each group to just do one angle and share results.
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Specular reflection vs scattering or diffuse reflection
Description:
Straight after investigating the law of reflection with a plane mirror the mirror can be replaced with some crumpled up aluminium foil to show scattering/diffuse reflection.
Some simple printed ray diagrams are available here.
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Pepper’s Ghost Demonstration
Description:
In this setup for Pepper’s Ghost a clean safety screen is used to create the partial reflection and a candle appears to keep burning when water is tipped into the beaker.
The effect is enhanced by hiding the candle that is burning underneath a heat proof mat which avoids the risk of things catching fire. Step by step set up is described in the video. Follow usual lab safety for naked flame.
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Demonstration of where the image is formed in a plane mirror
Description:
Using two rulers (or similar) one student adjust the position of one ruler in front and one behind a mirror so the second ruler behind the mirror coincides with the position of the image. The rest of the class look on from the side and can clearly see that the image is the same distance behind the mirror as the object was in front of the mirror.
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Drawing Ray diagram for a plane mirror
Description:
This overhead camera video is an ideal starting point for students to learn how to draw the ray diagram for a plane mirror on squared paper (1cm x 1cm squares). Using square paper avoids the need for a protractor. Just play the video and circulate around the room helping students who are stuck.
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Diffuse reflection visible light and specular �reflection infrared
Description:
If you have access to an infrared / thermal imaging camera a really interesting demonstration is that a brushed metal surface produces a clear image in infrared but not in visible light (see video on the right).
This is because for the longer wavelength infrared waves the surface is smooth enough for specular reflection.
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Simulations for plane mirror
Description:
Various simulations for reflection in plane mirrors the second part of this is a self paced lesson on how the image is formed in a mirror.
https://javalab.org/en/law_of_reflection_en/
https://simpop.org/reflection/reflection.htm
https://phet.colorado.edu/sims/html/geometric-optics-basics/latest/geometric-optics-basics_all.html
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Image or video
Simulation by PhET Interactive Simulations, University of Colorado Boulder (https://phet.colorado.edu), licensed under CC-BY-4.0.
The mirrors scope curved mirror illusion
Description:
A pound coin or similar small object placed on the lower mirror produces a real 3D image which appears to be floating in the hole in the upper mirror.
Ask students to try to draw the ray diagram to explain how the image is formed.
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Multiple images in two plane mirrors
Description:
A good extension activity. Tape a pair of mirrors together along one edge. You can then adjust the angle between the mirrors and observed how many images can be seen. A simple object such as a toy farm animal works well.
Other possible activities using multiple mirror: Construct a periscope:�https://learning.sciencemuseumgroup.org.uk/wp-content/uploads/2019/02/SMG-Learning-Activities-360-Periscope.pdf
Construct a kaleidoscope: https://www.youtube.com/watch?v=yShrIOj34r0
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Mirror illusion
Description:
A concertina is created so that when viewed in a mirror the reflection appears as a different work to the direct view. A lovely engaging trick developed by Matt Prichard who has kindly shared a downloadable template: Download the template from here
This is another interesting mirror trick shown in a video by Dan Jones.
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Image or video
Image used with kind permission of Matt Prichard
The legend of Archimedes using mirrors to set fire �to a Roman Ship in 214 BC - Is this possible?
Description:
There is a legend that Archimedes used mirrors to set fire to a Roman ship in 214 BC. This is an interesting story to discuss. See the link below for the MIT investigation and the link for the myth busters episode about it: https://web.mit.edu/2.009_gallery/www/2005_other/archimedes/10_ArchimedesResult.html
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Image: Public domain – Painting in the Uffizi
OK Go - Love
Description:
An amazing music video featuring multiple special effects using mirrors and robots. Impressive that it is shot as one continuous take.
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Mirror Maze or Laser Maze Game
Description:
You can either make a practical project to construct a mirror maze. This is shown in the video on the right and also described in this link - this could be a good science club project.
Or you can find various worksheet based challenges like this one which is free from Alex Johnston
And you can buy this commercial laser maze game.
Thanks to Paul Williamson for these suggestions.
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Light - Refraction
Refraction demonstration with laser, water tank� and smoke spray
Description:
Refraction of a laser beam is shown with the light entering water. The laser beam is made visible in the air using Magician Hazecan or fine water spray.
Follow usual laser safety precautions to avoid the laser light or reflections from entering anyones’ eyes.
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Change of speed with medium using two slinkys
Description:
To show the idea of a wave changing speed when it changes medium you can join a plastic slinky to a metal slinky. Then if you launch a longitudinal wave along the silky you can see it change speed at the interface.
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Image or video
Explaining refraction with wavefronts and PhET
Description:
The PhET animation bending light is really good zoomed in to help to explain refraction using the idea of wavefronts. The video goes through how to set it up.
You can use a role play of students to model this when they walk in a line holding hands to represent a wavefron and have to change to taking small steps when they cross the boundary to change medium.
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Ibn Sahl Role Model
Description:
Although Snell is often credited with the law of refraction. Ibn Sahl devised the law of refraction over 1000 years ago in his manuscript on optics in 984. He provides a more diverse role model to use in in lessons.��
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1000 Dinar Iraqi Banknote featuring Ibn Sahl
Cars and flooded road analogy to see that wavelength decreases�but frequency doesn’t change when a wave changes speed
Description:
A useful analogy (and animation) to show that the frequency of waves stays the same when they change speed is to think of cars slowing down when they get to a flooded section of road. This also shows the cars get closer together analogous to the wavelength decreasing as the waves slow down.
You can use the following animated PowerPoint slides or the video on the right.
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Refraction Model using toy car
Description:
A useful model/analogy for explaining refraction is the car driving from a road onto mud/gravel. The video on the right shows an actual car doing this. This PowerPoint slide has a simple animation of the same thing.
Whilst various sources and this video show a model demonstration it is very hard to get it to work convincingly in my experience so I recommend using a video or animation.
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Explaining refraction with car gravel analogy
Description:
A useful model/analogy for explaining refraction is the car driving from a road onto mud/gravel. The video on the right shows an actual car doing this. This PowerPoint slide has a simple animation of the same thing.
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Observing shallower apparent depth
Description:
If you look through a perspex/acrylic or glass block from its end at some printed text or writing you can see the shallower apparent depth.
For older students you can use the actual depth / apparent depth to estimate the refractive index by moving something up alongside the block until you judge it to be the same distance away as the writing viewed through the block. This BEST quick question is a good follow up with notes.
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Invisible Rube Goldberg Machine
Description:
This fun video has a Rube Goldberg machine / chain reaction machine which is made out of plastic which has the same refractive index as the liquid. So once the liquid is added you cannot see the pieces of plastic or the initial ball.
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Bent Pencil Refraction
Description:
A pencil dipped into a bowl or beaker of water appears bent in the water.
Requires a low viewing angle to work well (shown in the video)
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Disappearing test tube
Description:
Test tube of water and test tube of oil in beaker of oil. Because the oil has almost the same refractive index as the glass the test tube of oil becomes almost invisible because none of the light is refracted or reflected.
You can also use a glass rod or completely submerge a tiny beaker.
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Archer Fish and Refraction
Description:
Archer fish provide an interesting context to discuss refraction as they have to learn to aim in a different place to the apparent position because of refraction.
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Appearing lego figure with water beads
Description:
A lego figure (or similar) hidden amongst hydrated transparent water beads in a large beaker. It is hardly noticeable because the light if refracted by the water beads in lots of different directions. When water is added which has almost the same refractive index as the water beads the lego figure becomes visible because light is no longer refracted as it enters and leaves the water beads.
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Reappearing penny trick
Description:
A coin is attached to the bottom of a cup/bowl/opaque plastic beaker (you can use blue tac or similar). The observer moves until they just can’t see the coin. A second person pours in water whilst the observer is stationary and they can then see the coin.
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Detached head refraction illusion
Description:
A lovely demonstration where a playmobil person (or similar) appears to have its head detached when viewed from the corner of a rectangular tank in which it is partially submerged.
The video explains how to set it up.
This BEST activity uses a simpler method using a plastic block (notes)
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Patterned glass and syrup / rape seed oil
Description:
If you have some patterned or privacy glass you can change it to give a clear image of what is behind it by pouring on vegetable oil or syrup which has the same refractive index as the glass. Once the syrup/oil has made a flat surface a clear image is seen of whatever is behind the glass.
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Water bottle solar light
Description:
A simple solution to improve lighting in houses with a corrugated metal roof involves putting a plastic water bottle filled with water in the roof.
Provides a discussion of how this involves refraction and brings some diverse contexts into the lesson.
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Snell’s Window
Useful to know:
Description:
A diver or fish underwater looking up will view everything above the surface through a cone of light of approximately 97 degrees because light refracts towards the normal when entering the water. Beyond the cone the surface will appear dark or because of total internal reflection, a reflection of things underwater may be seen.
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Public domain from wikipedia
Refraction investigation with printed protractor
Description:
Semicircular blocks and a preprinted protractor make an investigation into refraction accessible and straightforward for younger or lower ability students.
Provided the ray is aimed at the centre of the semicircle it is only refracted once because it will exit the block along the normal. This makes it easier to interpret than using rectangular blocks.
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Mirages (inferior mirages)
Description:
In a common inferior mirage the surface of e.g. an asphalt road heats up in the Sun and warms the air directly above it lowering the air’s refractive index. This causes total internal reflection and makes the road surface appear like the surface of water / a mirror.
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Image by Mike Run CC BY-SA 4.0 from wikipedia
Image by Yuri Khristich given to Public Domain from wikipedia
Superior Mirages - floating ship illusion
Description:
A quick google search will yield some images of floating ships
Such as this one https://www.bbc.co.uk/newsround/56290511
which are called superior mirages. The diagram on the right shows how they can form by the refraction of light.
Reinforces the idea that the brain assumes that light has always travelled in a straight line when working out where something is.
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Links and where to find further information:
Image by cmglee (talk · contribs), Antilived (talk · contribs), Jmarchn (talk · contribs) - Own work Pirate ship.svgFemale shadow lateral.svg, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=155378786
Refraction investigation with full ray tracing
Description:
For older students or if you have more time then doing complete ray tracing for an investigation into refraction is a good idea.
Showing the steps with an overhead camera video is helpful to communicate the method.
This is the BEST description of this activity with notes. Or use slide 22 onwards of these BEST slides with notes.
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Refraction and reflection investigation with full ray tracing
Description:
For the AQA GCSE Physics required practical students have to measure the angle of incidence, refraction and reflection with a rectangular block for two different materials.
Showing the steps with an overhead camera video is helpful to communicate the method.
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Refraction of liquids tank
Description:
These tanks (United Scientific Reflection & Refraction Tanks) are bought and use a built-in battery powered class II laser (output power<1mW) attached to the tank on a rotating arm. You can set the laser above the liquid so the pathway is air to liquid, or liquid to air as shown in the picture.
Follow usual Laser safety
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Light - Colours
Why do objects look coloured?
Description:
Series of slides to discuss why objects look coloured. Lots of repetition. Works well for questioning with mini whiteboards.
This BEST cloze absorb/reflect activity and notes is useful for checking student understanding. And this football kit BEST activity and notes is also worth a look.
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Dispersion simulations
Description:
Both the PhET bending light simulation and this Javalab one are good for simulating how to make a spectrum with a triangular prism.
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Links and where to find further information:
Simulation by PhET Interactive Simulations, University of Colorado Boulder (https://phet.colorado.edu), licensed under CC-BY-4.0.
Producing a nice spectrum for classroom demonstration
Description:
Key to this is projecting an image of a white slit onto a screen/wall and then inserting either a triangular glass prism or a diffraction grating in to make the spectrum. The video discusses this.
If you have an old fashioned slide projector then it is very easy to set up. Old OHP projectors are also good.
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Practical to produce a spectrum with triangular prisms
Description:
White light from a ray box is directed towards a triangular prism perspex/acrylic/glass which is then rotated to produce a spectrum. It is easier to see the spectrum further from the prism. It is helpful to bend the edge of a piece of paper up.
If using glass be careful of sharp edges created if the prism has been chipped. Warn students that metal ray boxes may get hot. This BEST diagnostic and notes is a good hinge question afterwards.
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Round bottomed flask or crystal ball rainbow
Description:
Sunlight or a very bright slide projector is shone through a circular hole in the middle of some sugar paper or cardboard. Total internal reflection takes place in the crystal ball or round bottomed flask full of water and produces a circular rainbow on the card around the hole. The round bottomed flask or crystal ball is acting in a similar way to the water droplets which create a rainbow.
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Appearance under coloured light demonstration
Description:
A remote controlled LED light bulb (something like this with a minimum power of 10 W) is changed from red to green and writing appears on a piece of paper.
Needs the room reasonably dark but not perfect black out blinds. Drawing on graph paper helps to distract the eyes from any slight remaining image than white paper. Putting the graph paper in the back of a black crate/box and facing it away from any remaining light sources helps. Use a light red pencil to draw the design.
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Coloured light mixing demonstrations
Description:
You can buy dedicated colour mixing demonstrations like the lascelles one shown in the video. But you can also achieve the same effect a little more cheaply using this set of three LED coloured torches which are quite bright.
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Colour mixing investigation with PhET
Description:
You can either demonstrate colour mixing with the PhET simulation on the board or you can get students to do a simple investigation on their own devices in which they have to try to create different colours. This is described in the Colour simple investigation on https://www.pheteffect.com/waves which includes slides and teacher notes.
Good to link to how a LCD display works with pixels of only red, green and blue colours.
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Links and where to find further information:
Simulation by PhET Interactive Simulations, University of Colorado Boulder (https://phet.colorado.edu), licensed under CC-BY-4.0.
Demonstration of the action of coloured filters
Description:
The demonstration that a colour filter only transmits light of the colour that it is can be easily demonstrated by creating a spectrum and then inserting different coloured filters in turn.
See the earlier idea slide about producing a good spectrum.
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Links and where to find further information:
Class Practical of the action of coloured filters
Description:
As an alternative to demonstrating the action of coloured filters students can observe it in a practical. After making a spectrum using ray boxes and triangular prisms (see earlier idea slide) red and green filters can be inserted either before or after the prism to show the action of the filter.
Warn students that metal ray boxes may get hot.
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Links and where to find further information:
Fun colour filter demonstration
Description:
This is lovely demonstration where the students see a different message on the screen depending on whether they look through a red or green filter.
You can edit the message on these slides.
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Carnovsky Art
Description:
Italian artist duo Carnosky produces art which has three different pictures depending on whether it is viewed under red, green or blue light (or viewed through red, green and blue filters).
This is a good extension to simpler demonstrations with coloured light or filters.
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What colour does it look simulations
Description:
This simulation lets you set up a coloured light bulb with a coloured duck viewed through a colour filter and then to reveal how the duck will appear. Works well either on the board with mini whiteboards to predict the appearance or by students using it individually on their own devices.
https://javalab.org/en/color_en/
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Screen shot used with permission from Javalab What colour does it look?: https://javalab.org/en/color_en/
Light - Lenses
Crystal ball fires to introduce lenses
Description:
Crystal ball fires are an interesting way to introduce a lesson on lenses. You can find an up to date new story and then discuss using a ray diagram how the sun light would refract as it passes through the crystal ball.
Slides including ray diagrams and photos here.
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Making a raybox projector
Description:
I discovered this activity in the excellent Physics for You textbook by Keith Johnson. Students draw a simple image on a piece of tracing paper and place it instead of the slits in a raybox. Then using a convex lens (approx 20 cm focal length) the students can project an image of their design onto a piece of paper or mini whiteboard about 0.5m away.
Warn students that metal ray boxes may get hot.
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Modelling a simple convex lens using PhET
Description:
The PhET bending light simulation is used to model a how a simple convex lens shape can cause parallel rays to converge.
The video shows the steps to construct a simple lens shape and to test it.
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Reversing arrow activity
Description:
Students move a glass or beaker of water and make a horizontally dawn arrow reverse its direction. It is a good way to introduce the key terms for describing the image formed by a lens. Can also be used as a fun science club activity.
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Forming the three different kinds of images �with a convex or converging lens
Description:
Giving students convex/converging lenses of around 20 cm allows them to easily form the three possible kinds of images. Carbon filament lamps or other light bulbs with filaments whose shape makes it clear which way up they are make ideal objects.�If you close all the blinds in the room apart from one students can make a diminished image of the view through the remaining window.
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Step by step ray video to draw lens ray diagrams
Description:
Teach drawing ray diagrams by playing a step by step video with overhead camera and students draw along on squared paper (1cm squares). Teacher circulates providing additional help as needed.
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Perspex/acrylic models of lenses with ray boxes
Description:
Plastic blocks shaped like convex/converging and concave/diverging can be placed in front of a ray box with the slits orientated to provide 3 or 5 rays of light. The action of the lens can clearly be seen. It works well if you completely remove the slits from the ray box as well.
Can also be done as a demonstration using a visualiser to provide an overhead view. Warn students that metal ray boxes may get hot.
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Links and where to find further information:
Jelly lens models
Description:
As an alternative to using plastic shapes with ray boxes to model lenses you can make a lens shape out of colourless jelly. Instructions and write up from the Irish Science on stage website here.
You can cut successively thinner less curved lens and show the focal length increasing.
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Structured Lenses Investigation with PhET
Description:
Students create the different lens ray diagrams using the PhET simulation Geometric Optics see
https://www.pheteffect.com/waves for slides and teacher guide for the activity.
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Useful to know:
Links and where to find further information:
Simulation by PhET Interactive Simulations, University of Colorado Boulder (https://phet.colorado.edu), licensed under CC-BY-4.0.
Partially blocking a convex/converging lens
Description:
An interesting demonstration a lens is used to form an image. Then a piece of card is used to cover half or more of the lens. Although the image gets dimmer the whole image is still visible. This shows that the light forming the image travels through all parts of the lens. Students are often surprised by this demonstration.
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Model Telescope
Description:
A model telescope is constructed by attaching two convex (converging) lenses to a metre ruler. Ideally you want one with a roughly 10 cm focal length for the eyepiece lens and 40-50cm lens for the other one. If you attach the lenses to the metre ruler with a gap equal to the sum of their focal lengths they will only need a minor adjustment in position to produce a sharp image.
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Everyday uses of lenses
Description:
Ask students to suggest/research as many different uses of lenses in everyday life as they can find.
See image for a few possible answers.
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Links and where to find further information:
Image or video
Fluorescence model eye with round bottomed flask
Description:
A lovely demonstration where a round bottomed flask filled with fluorescence models the eye. Light produced by an old slide projector (or bulb and lens) is visible as it passes through the fluorescence. Different lenses on the front of the flask can represent long and short sightedness. And additional lenses can then be inserted to correct it. See the link below for full instructions about which kind of lenses to use.
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Eye and sight correction simulations
Description:
A lovely context for teaching about lenses is the correction of short and long sight. This is something students can relate to. Be careful to be sensitive to anyone who wears glasses or contact lenses.
This simulation is a great way to discuss how to fix it and you can try inserting either kind of lens.
https://javalab.org/en/correction_of_near_sightedness_en/
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Screen shot used with permission from Javalab Correction of Near and far sightedness https://javalab.org/en/correction_of_near_sightedness_en/
Light - Total Internal Reflection
Physics is magic or not
Description:
A demonstration or practical using two plastic cups (you can use a piece of paper in a small plastic bag instead). When the double cup is dipped in the water and viewed from a suitable angle you can only see the writing on the outer cup and not the inner cup because of total internal reflection.
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Vanishing coin total internal reflection
Description:
When viewed through the side of a beaker the coin underneath a glass beaker disappears when water is added to the beker because of total internal reflection.
A piece of card over the top of the beaker stops observers looking through the top and seeing the coin.
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Image or video
Total internal reflection and soot
Description:
A silver coin is covered in soot in a candle flame and becomes black. It is then dipped into a beaker of water and appears silver.
The soot is hydrophobic and traps a layer of air on top of it. Total internal reflection occurs at the water air boundary and so the coin appears silver as the light is reflected before it reaches the soot.
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Total internal reflection in a water tank
Description:
A water tank is used to demonstrate total internal reflection by directing a laser at an angle greater than the critical angle at the interface of the water with the air.
Add a few drops of milk to the water tank to make the laser beam visible.
Usual laser safety needed to ensure laser or reflections don’t go into anyone’s eyes.
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You can relate this to seeing total internal reflection in the surface of water in an aquarium/fish tank.
Links and where to find further information:
Measuring the critical angle
Description:
Simple practical using a semicircular block. The angle of incidence is slowly increased in order to find the critical angle at which the light is refracted along the edge of the block and then total internal reflection begins.
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Total internal reflection in a water stream
Description:
The easiest setup for this is to make a small circular hole in a plastic bottle and line a laser up from the other side of the bottle with the hole. The laser is totally internally reflected inside the stream of water. It can help to stick a short piece of plastic or glass tube horizontally to the bottle to get a clean flow.
Usual laser safety needed to ensure laser or reflections don’t go into anyone’s eyes.
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Simulations for total internal reflection
Description:
Several good options for showing total internal reflection as a simulation. The java lab one is nice for showing an optical fibre.
https://javalab.org/en/total_internal_reflection_en/
https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_all.html?screens=1
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Screen shot used with permission from Javalab Total Internal Reflection and Optical Fiber https://javalab.org/en/total_internal_reflection_en/
Optical Fibre Transmission Demonstration
Description:
You can buy complete kits which will transmit a signal by modulating a laser to demonstrate e.g. music being sent via an optical fibre link. The video shows one in action firstly without an optical fibre and then with the signal going through and optical fibre.
If a laser is used then follow usual laser safety to ensure laser or reflections don’t go into anyone’s eyes.
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Model of optical fibre
Description:
A curved piece of acrylic can be used to show repeated total internal reflection by shining a ray box / laser ray box or laser pointer through it. Can easily be demonstrated to a class using a visualiser.
You can alternatively make one out of transparent jelly.
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Total internal reflection with violet laser in tonic water
Description:
If you have a 405nm violet laser then it will cause fluorescence in tonic water that has quinine in it.
You can get total internal reflection from the side of the bottle which looks rather nice.
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First optical fibre link in public phone network
Description:
This was built between Hitchin and Stevenage in Hertfordshire by STC based in Harlow in 1977. You can see a real of the fibre in the science museum in London.�
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Role Model - Charles Kao
Description:
Charles Kao (1933-2018) was a physicist and electrical engineer who is best known for his work on the development and use of fibre optics in telecommunications. Born in Shanghai, his early education was in Hong Kong. He moved to London where he completed his PhD. He was awarded the 2009 Nobel Prize in Physics for "groundbreaking achievements concerning the transmission of light in fibers for optical communication".
Text used with permission from OCR STEM Contributors resource which you can access directly using the link below.
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By David Dobkin [1] - http://www.cs.princeton.edu/~dpd/Dean OfFaculty/person_FILES/Charles.Kao.html, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8000542
Undersea cable map
Description:
An interactive map showing submarine optical fibre cables. Interesting to explore when discussing total internal reflection and optical fibres:��https://www.submarinecablemap.com
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Screenshot from https://www.submarinecablemap.com �under Creative Commons License: Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
Bicycle Reflector Model
Description:
Using triangular prisms and a laser pointer or ray box the double total internal reflection sends the light back in exactly the opposite direction it has come from.
The same principle is used in bicycle (and car) reflectors so that the reflected light goes back towards the car whose headlights produced it.
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Bending a laser in sugar solution
Description:
A narrow tank is filled with hot water (don’t exceed the temperature your tank can take) and sugar cubes added along the length. The tank is then left undisturbed overnight. A laser bends because the refractive index varies with the concentration of sugar which increases towards the bottom of the tank.
Usual laser safety needed to ensure laser or reflections don’t go into anyone’s eyes.
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TV rock - Ulexite
Description:
Ulexite is a naturally occurring mineral with a crystal structure like a bundle of optical fibres. If you places polished piece of it over a picture or some text then the image underneath it appears as if it is coming from the top of the sample. It is a striking effect.
Once sample is quite cheap to buy and can be passed around the whole class.
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Electromagnetic Spectrum
Parabolic reflection of infrared
Description:
The video shows a nice demonstration of lighting a match using parabolic reflectors of infrared. A simpler demonstration where you can feel the infrared reflected is to make a curved piece of aluminium foil by wrapping it around a football. If you place it behind a carbon filament lamp you can feel the increase in infrared radiation reflected on the other side using your hand.
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The story of the invention of the microwave oven
Description:
The idea for a device that uses microwaves to heat food came to Percy Spencer in 1945. At the time, he was working for Raytheon, the American defence and industrial corporation which had the first contract to mass produce magnetrons, devices that emit microwaves. These had been used as a component of radar systems during the Second World War. After walking past a working magnetron, Spencer discovered that the confectionery bar in his pocket had melted, even though he had felt no sensation of heat. Whilst many books report that the bar Spencer carried was made of chocolate, Spencer’s grandson, Rob, has claimed that it is more likely that the bar was a peanut cluster as his grandfather often carried one to feed squirrels and chipmunks. After noticing the melted bar, Spencer is reported to have sent a messenger boy to get some corn kernels and produced the first batch of microwave popcorn. The following day, he used the magnetron to cook an egg and watched as it began to tremor and quake. A curious colleague who moved in for a closer look was splattered with hot yolk as the egg exploded in his face.
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Herschel experiment
Description:
If you are blessed with a sunny day at the right time you can do Herschel’s experiment with a box, glass prism and blackened thermometer bulbs. See IOP description here.
I made a modern version using a thermal imaging/infrared camera to monitor the temperature of the different parts of the spectrum which gives faster results.
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Image or video
UV beads and sunscreen investigation
Description:
Either as a demonstration under a visualiser a layer of UV beads is covered in cling film or put inside a thin plastic bag and part of the bag is covered with sunscreen. They are then exposed to UV either by taking outside in the Sun or using a UV lamp. You can then observe how quickly the colour changes in the areas with and without sun cream. Good to relate to avoiding sunburn and skin cancer. Careful risk assessment and choice needed for UV lamp use.
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UV lamp security pen etc
Description:
An engaging demonstration when discussing UV is to draw or write something interesting on the table using a UV security pen (which are intended to label belongings with so that the police can discover the owners when they recover stolen good). You can then reveal the writing or drawing using a UV lamp.
Use low power UVA torch, keep fingers away from the source and point it away from skin and eyes. See the latest UV safety guidance from CLEAPSS or similar.
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UV cured nail polish/gel
Description:
After each coat is applied the nails are cured under a UV lamp. The UV has sufficient energy to be absorbed by bond which then splits leaving an unpaired electron which then forms a bond with another electron. This causes monomers to join together to form a long chain polymer which causes the nail polish to change from a liquid into a solid.
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Simulation for Electromagnetic Spectrum
Description:
This simple simulation lets students quickly see how the wavelength of ultraviolet infrared compares to visible light.
https://javalab.org/en/electromagnetic_waves_around_of_visible_rays_en/
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Microwave detector
Description:
You can buy these cheapply from the usual online retailers to detect microwaves from microwave ovens, wifi routers and phones. They are tuned to the frequency of microwave ovens but detect 2.5 GHz wifi pretty well.
Thanks to David Ridings for sharing the idea
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Demonstration of microwave transmitter and receiver
Description:
With school demonstration microwave transmitter and receivers you can show simple properties of microwaves such as reflection shown in the video.
If you have the ability to do external modulation of your microwave transmitter it is more interesting if you modulate audio output from a computer instead of the 1kHz buzz - although the quality of the music is not very good.
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Radio waves animations
Description:
To teach the basic idea of how a radio wave is transmitted and received and can be reflected from the ionosphere using some simple PowerPoint animations is helpful.=
You can also use the old PhET radio waves and electromagnetic fields animation a screen recording of the PhET video is provided as it can be slow to load the legacy simulation. This is a derivative of the PhET original and runs better.
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Role Model - Jahangir Shah Broadcast Engineer
Description:
Jahangir Shar is a broadcast engineer who has worked for the BBC and Sky. He completed his engineering degree through an apprenticeship at the BBC. He uses his knowledge of physics (including sound, light and electricity) and technology, along with team management skills, to make sure that if one system fails, the show goes on.�Text used with permission from the OCR STEM contributors resource. Use the link below to access it.
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Hertz Radio wave demo
Description:
A simple demonstration using a piezoelectric sparker to produce a spark in a small gap between two pieces of copper wire. The radio waves produced are detected a short distance away with another two pieces of copper wire with a neon indicator lamp connected between them.
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UV premature ageing of skin photograph
Description:
This photograph of a truck driver who has aged on the side of his face which had the sun coming on to it through his open window for a career is a really interesting way to start discussion about premature ageing of skin caused by UV.
It starts an interesting discussion to put up the photo and ask students what they notice and can they think of an explanation for it.
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Forming an X-ray image
Description:
This simple PowerPoint animation shows the basic idea of an X-ray image formation.
There are some nice PowerPoint slides with example basic X-ray images and CT scan which can be downloaded from the IOP here: https://spark.iop.org/x-ray-imaging
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Infrared Radiation and Black body radiation
Californian squirrel tail swishing to fool rattlesnakes
Description:
Rattlesnakes have pits which detect infrared which are used to catch prey. To confuse the snakes the Californian ground squirrels pumps extra blood to its tail to make it hotter and give out more infrared and then flick the tail around.
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Leslie cube and emission of radiation
Description:
For experiments looking at emission of radiation you have a few different options for detecting the infrared. These are discussed in the video. An infrared detector for a data logger is nice because it directly gives you the intensity of radiation in W/m2 whereas if you use an infrared thermometer or camera it converts the intensity into a temperature based on an assumed emissivity. You then have to use the apparent temperature as a measure of the infrared emitted. Take care not to touch hot surfaces.
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Additional notes about Leslie Cube and Beaker cooling
Further Guidance:
If you have a Leslie cube that you want to adapt to have a silver surface then a quick way to achieve this is to stick aluminium tape onto it. You can buy aluminium tape from usual online retailers or DIY stores. The silver surface gives a very low emissivity and so barely any radiation is detected from it. This is shown in this video made by David Richardson and Lewis Matheson).
If you don’t have a suitable infrared detector you can just wait for small black and silver mini drinks cans to cool as shown in this video. The silver can was made using aluminium tape. In the video they had painted the other can with matt black tape but you can buy black aluminum tape which I think would provide a fairer comparison but I haven’t tried it.
Burnt toast and understanding the disappearing ice sheets
Description:
It is challenging to toast bread to the perfect colour because of thermal runaway: as the surface of the bread darkens it absorbs more thermal radiation so its temperature rises faster and the blackening process accelerates. A more serious but related effect occurs as highly reflective white ice sheets melt, decreasing the net reflectivity of the Earth’s surface and accelerating global warming.
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Image and text used courtesy of the IOP and Richard Brock
Absorption of radiation using take away trays
Description:
To demonstrate absorption of radiation by different coloured surfaces two aluminium takeaway tubs are used (one coloured in black with a marker pen and the other left silver). Temperature probes or thermometers are attached on the other side and a filament lamp is placed in the middle. Data logging the temperature-time graph shows that black is a better absorber as it heats up faster and to a higher temperature. Can also use mini drinks cans shown in this video
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Discussing blackbody radiation with the PhET simulation
Description:
The PhET simulation Blackbody spectrum is useful when teaching how the spectrum changes with temperature.
Teacher guidance and a set of slides is provided on
https://www.pheteffect.com/waves for running a class discussion about it.
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Observing the wavelength of radiation �change with temperature
Description:
Gradually heating up short piece of 36swg Nichrome resistance wire with a continuously variable 12V power supply and viewing it through a large diffraction grating film (either 500 or 1000 lines per mm) makes it easy to see how the spectrum changes. In the video I also used an infrared camera to show that before visible light is emitted but the demo works well without it.
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Image or video
Simple animations to discuss the effect of radiation �emitted and absorbed on the temperature of the Earth.
Description:
A PowerPoint slides with a series of simple animations and discussion questions to think about the radiation absorbed and emitted by the Earth and the effect on the temperature of the Earth.
Works well to use before the PhET greenhouse effect simulation (see next slide)
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The PhET Greenhouse effect simulation
Description:
Screen 1 of the PhET greenhouse effect simulation is good for showing the shorter wavelength radiation coming in from the Sun and the longer wavelength radiation being emitted by the Earth. You can adjust the greenhouse gas concentration or click on the calendar symbol to adjust by date (which I think is more engaging for students).
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Image or video
Demonstrating the greenhouse effect �with an infrared camera
Description:
This demonstration/video uses a carbon filament lamp to represent the Sun, a globe to represent the Earth and a sheet of glass to represent greenhouse gases in the atmosphere.
The thermal imaging camera can shows that the shorter wavelength infrared from the hot filament lamp is transmitted by the glass but the longer wavelength infrared radiation emitted by the globe is reflected and absorbed by the glass.
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Why does it get colder on a winter night when �there is a clear sky than when it is cloudy?
Description:
This makes a great next time question. The video of the cloud and bluesky could provide a stimulus for the discussion.
The answer is of course that the cloud reflects infrared radiation emitted by the ground back down on to the ground so less infrared radiation is emitted into space and so the ground (and air below the cloud) stays warmer.
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Doppler Effect
Doppler Effect Animations
Description:
Lots of choice of great animations to use when discussing the doppler effect. Take your pick
Doppler Effect - Javalab �Doppler effect and Doppler Effect �The Doppler Effect & Sonic Boom �Doppler Lab �Doppler Effect Sound Wave JavaScript Applet �https://interactives.ck12.org/simulations/physics/doppler-ducks/app/index.html?screen=sandbox
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Screen shot used with permission from Javalab Doppler Effect: https://javalab.org/en/doppler_effect_en/
Buzzer in a bag doppler effect demonstration
Description:
Swinging a buzzer round in a bag, students can hear the doppler effect (higher pitch as the buzzer moves towards them and lower pitch as the buzzer moves away form them).
Safety: Make sure that the buzzer is secure to avoid the risk of it flying into the audience.
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Doppler Effect with car horn video
Description:
A useful video clip of the doppler effect as a car sounding its horn drives past the observer. You can clearly hear the change in pitch from higher to lower as the car changes from moving towards the camera person to moving away.
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Image or video
Doppler effect with swinging bluetooth speaker and PhyPhox App
Description:
A nice experiment described by the Perimeter Institute using the PhyPhox app to measure the frequency of a swinging bluetooth speaker giving a constant frequency tone.
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Doppler Effect with Microwaves
Description:
The doppler effect can be demonstrated using microwaves. The transmitter should be unmodulated (not possible on all school 3cm transmitter kits). The receiver should be positioned so it gets some microwaves direct from the transmitter and some from a metal sheet which is moved. The two waves interfere and create an audio frequency beats which can be heard through a loudspeaker and displayed on an oscilloscope which can then be used to calculate the speed of the sheet.
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Seismic Waves
Plasticine balls to introduce the idea of investigating �the Earth’s structure with seismic waves
Description:
Two plasticine balls are shown to students (one has a steel ball bearing in the middle of it which makes it noticeably heavier). A sequence of questions gets students to think about why it might be heavier and how the different possible theories could be tested. And then to think which ideas could be applied to investigate the structure of the Earth.
This video explains how to sequence it: https://www.earthlearningidea.com/Video/V20_Clay_balls.htm
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Shadow zone with light demonstration
Description:
A circle is drawn to represent the Earth. A beaker of water is placed in the centre to represent the inner and outer core of the Earth. When light is shone through the beaker to represent P-waves the refraction creates a shadow zone on the other side of the Earth. The beaker is then wrapped in black paper and then no light can pass through the beaker (core) representing S-waves which produces the complete shadow zone.
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Image or video
Role play P and S waves with solids and liquids
Description:
Students standing in a line represent particles in solids (linked arms) or liquids (not linked) and you can demonstrate that a transverse (s wave) cannot travel through a liquid but a longitudinal wave (p wave) can. The link at the bottom of the slide has a lot more detail in it.
This video shows a rather more controlled version than the one linked on the right.
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Seismic wave animations and simulations
Description:
This first animation shows P- and S- waves as longitudinal and transverse respectively:
https://javalab.org/en/seismic_wave_en/
This second simulation shows how the P- and S- waves propagate through the Earth using real data
https://ds.iris.edu/seismon/swaves/index.php
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P and S waves on vertical slinky
Description:
A simple demonstration with a slinky hanging vertically you can create just longitudinal waves (P-waves) by displacing it vertically and releasing. Just transverse waves (S-waves) by displacing it horizontally and releasing it. Finally you can simulate what happens in a real Earthquake by displacing the slinky at an angle which creates both longitudinal and transverse waves.
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Role Model Inge Lehmann
Description:
Inge Lehmann (1888 - 1993) was a Danish seismologist and geophysicist who discovered that the Earth has a solid inner core in the centre of the liquid outer core.
She overcame many challenges as a woman working in STEM and was the first to interpret p-wave arrivals as reflections from the inner core of the Earth in 1936. Prior to this the Earth’s core was believed to be entirely liquid.
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Image or video
Image public domain from wikipedia
Role Model Adriana Ocampo
Description:
Adriana is a Colombian planetary geologist with a long distinguished career studying geology of different planets and moons in the solar system.�
In 2015 she started to serve as the lead program executive for the New Frontiers Program at NASA’s Jet Propulsion Lab. In 2003 she had an asteroid named after her.
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Image or video
Image: Public domain from NASA
Diffraction
Diffraction of water waves
Description:
You can find some lovely photographs of water waves diffracting through small gaps such as the one shown.
Good to show alongside demonstrating diffraction in a ripple tank.
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Wave diffraction Oualida lagoon, south of Casablanca 16-06-2023. Google Earth image use permitted for non-commercial purposes.
Demonstrating diffraction with a laser and �adjustable width single slit
Description:
Shining a laser through and adjustable width single slit is a lovely demonstration. If you don’t have an adjustable width single slit you can use two razor blades facing each other and slide them closer or further apart.�Usual laser safety needed to ensure laser or reflections don’t go into anyone’s eyes.
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Single slit diffraction with white light
Description:
It is difficult to create a projection of single slit diffraction with white light. However, if you put a single slit over the camera on a smartphone and point it at a thin filament bulb filament or similarly narrow white light source you can see the diffraction pattern with a wide central white fringe where all the wavelengths constructively interfere surrounded by subsidiary maxima which are little spectra.
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Demonstrating diffraction with sound waves
Description:
Diffraction of sound waves can be shown using a loudspeaker connected to a signal generator and using two pieces of hardboard to create a slit. A microphone behind one piece of the hardboard detects a greater amplitude of sound when the second piece of hardboard is moved in to create a slit of a similar size to the wavelength of the sound.
�Ensure volume is not loud enough to damage anyone’s hearing
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Demonstrating diffraction with microwaves
Description:
Diffraction of 3 cm microwaves can be demonstrated by showing that a receiver offset to the side of the transmitter detects a greater amplitude of microwaves as a slit is created using two pieces of metal.
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Polarisation and scattering
Crossed polarisers (including viewing stress)
Description:
Crossed polarisers block all the light from going through them. If you insert transparent plastic ruler, protractor etc in the middle then you can see the stress patterns which are locked into the plastic.
This is an example of stress induced birefringence which has a wavelength dependence and hence the colours are seen
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Polarisation Simulations
Description:
There are plenty of online simulation showin polarisation. I like this first one because it works well alongside the microwave polarisation demonstration.
https://javalab.org/en/polarization_en/
This one is good for discussing the crossed polarisers with a third one inserted at 45o
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Screen shot used with permission from Javalab Polarisation: https://javalab.org/en/polarization_en/
Polarisation With microwaves demonstration
Description:
You can demonstrate polarisation with 3 cm microwave transmitter and receivers and a metal grille. You can show that the microwaves produced are polarised by rotating the transmitter or receiver by 90o. When the metal grill is oriented parallel to the polarisation of the microwaves then they are absorbed by the metal as the electrons in the metal can oscillate and therefore the microwaves are not transmitted past the grill.
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Polarisation and aerials for TV and radio
Description:
You can use some photographs of terrestrial TV and radio aerials to discuss the likely polarisation of the radio waves they are receiving.
Most terrestrial TV broadcasts in the UK are horizontally polarised whereas the FM radio broadcasts are vertically polarised.
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Links and where to find further information:
By Carnby - Self-photographed, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=23590373
Photo by Simon Poliakoff CC BY-NC-SA 4.0
Terrestrial TV aerials
FM radio aerial
Polarisation and 3D glasses
Description:
Polarisation is commonly used to create a 3D effect in cinemars and some televisions. Polarising filters are used so that each eye receives a slightly different image which the brain interprets as a 3D image.
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Polarisation of light and navigation by bees
Description:
Bees have eyes that can detect the polarisation of light which allows them to navigate using the Sun even when it is cloudy. The video shows a model made using polarising filters to show how you can work out the direction to the Sun.
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Crossed polarisers with 3rd at 45 degrees
Description:
A horizontal polarising filter followed by a vertical polarising filter block all the light. But if you insert a third polarising filter in the middle at 45 degrees you once again get some transmitted light.
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Polarisation by reflection
Description:
You can demonstrate that reflected light is polarised by putting a safety screen flat on a desk with black sugar paper underneath it below a window. Standing in a position such that you are close to the brewster angle you can rotate a polarising filter and make the reflection almost completely disappear. Lost of students can do this at once if you have plenty of polarising filters.
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The magic LCD screen
Description:
It is possible with care to remove the final polarising filter from an old LCD screen which you then can connect to a computer etc. The screen appears completely white until you look at it through a polarising filter or polarising sunglasses and then you can see what is meant to be displayed.
A fantastically engaging demonstration with a huge wow factor.
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Corn syrup polarisation
Description:
Corn syrup e.g. Karo corn syrup widely available in the USA is optically active and rotates the polarisation of plane polarised light as it passes through it. If you place a beaker of corn syrup between two crossed polarisers and rotate one of them you can select different colours because the rotation of the polarisation has a wavelength dependence.
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Spot the hidden cellophane
Description:
A piece of cellophane in a boiling tube of glycerol is invisible because the cellophane and glycerol have the same refractive index. However, if you place the boiling tube between crossed polarisers you can easily see the cellophane. Thanks to Andres Tretiakov for sharing the idea and making the example used in the video for me.
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Calcite Crystals Birefringence
Description:
Calcite has two refractive indices depending on the polaristaion of the light. It makes a lovely next time / research question to demonstrate and ask students to explain it in the next lesson.
It works well to hand around the class together with a polarising filter and each student or pair to look at some writing in their book or print in a text book and rotate the polarising filter. You can also show it under a visualizer to a whole class at the same time.
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Blue sky and sunset demonstration
Description:
Fill a long tank with water and add small amount of milk. Then shine a bright torch or ideally an old slide projector in from one end. Viewing form the side the light looks blue because of fat globules scattering the light which happens more at shorter wavelengths. This is the same process that makes the sky blue. If you then view the light source form the opposite end of the tank it will look yellow/orange as you are seeing the light which hasn’t been scattered (like seeing the Sun at sunset) when the light is travelling through a lot of atmosphere.
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Superposition and Interference Basics
Phase mini whiteboard quiz
Description:
This short set of slides is useful for a mini whiteboard quiz to check students understanding of phase and phase difference between two waves and between two parts of the same wave.
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Superposition of waves simple pulses simulations
Description:
A range of useful animations to show superposition of wave pulses. Run this one at slow animation speed to see the idea of superposition.
https://ophysics.com/w2.html �Also try this one:�https://javalab.org/en/superposition_and_interference_en/
�Use this one to predict what the resultant wave will look like, draw it and then tick show pulse sum to compare your answer.
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Ice Road Truckers why they slow down as they pass?
Description:
Wave travels in front of the trucks as they travel along on the ice roads. Why must the trucks slow down when they pass one coming in the opposite direction?
Answer = the two displacements of the waves in front of the trucks superpose and add together which can be enough to break the ice.
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Interference with monochromatic light and two glass plates
Description:
The traditional version of this demonstration involves using a low pressure sodium lamp as a monochromatic source of light. However, a colour changing LED lamp/bulb works very well set to red.
Light is reflected from the two surfaces of glass which are touching each other and interferes to produce dark and bright fringes. Pushing the glass together changes the path difference and so the spacing of the fringes.
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Thin film interference oil and soap films
Description:
Thin film interference occurs when light reflected from the front and back of the oil layer or inside and outside surface of the bubble interferes. Depending on the thickness of the film and the viewing angle it will be constructive for different colours and hence the beautiful colours observed.
Here are instructions for giant bubble mixture and wand - also makes a great science club activity.
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Photo: Simon Poliakoff
Katharine Blodgett Role Model
Description:
Blodgett used a barium stearate film to cover glass with 44 monomolecular layers, making the glass more than 99% transmissive and creating "invisible" glass.
The visible light reflected by the layers of film cancelled the reflections created by the glass.
Useful in cameras, microscopes etc
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Image used from Smithsonian Archives: https://www.si.edu/object/katharine-burr-blodgett-1898-1979-demonstrating-equipment-lab:siris_arc_290343
Structure for explaining wave interference effects
Description:
Students often struggle to write good explanations of interference effects with waves. The following slides contain the structure shown with suggested key words and phrases for each section.
Best to model some examples and then get students writing their own.
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Rotation tuning fork and hearing interference
Description:
This is a lovely super quick practical when starting teaching wave interference or discussing noise cancelling headphones. If you slowly rotate a tuning fork next to your ear it goes through loud and quiet positions. This is caused by the waves from the two prongs of the tuning forks constructively or destructively interfering.
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Demonstrating beats with two tuning forks �or two loudspeakers with signal generators
Description:
Beats are easily demonstrated with two large identical tuning forks onto one of which something is attached to slightly alter its frequency. Alternatively you can use two signal generators set to slightly different frequencies or use the simulations linked from the useful to know section.
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Interference with microwaves
Description:
A 3 cm microwave transmitter and receiver are used to demonstrate interference. The microwaves are partially reflected from a hardboard sheet and also reflected by a metal sheet further away. The two waves interfere. Moving the metal sheet changes from constructive to destructive interference. The distance moved between consecutive positions of constructive interference is half a wavelength as that increases the path length by one whole wavelength.
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Michelson Morley interferometer model with microwaves
Description:
A model of the michelson morley interferometer is made using 3cm microwave transmitter and receiver. A plastic or hardboard sheet is used as the partial reflector/beam splitter and metal sheets are used as full reflectors.
Helps to have a 3D representation to bring this historical experiment to life.
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Lego Interferometer
Description:
A team at the University of Nottingham have designed an interferometer made almost entirely out of lego. You can access all the instructions and resources from here:
https://artlab-nottingham.com/lego/
Usual laser safety needed to ensure laser or reflections don’t go into anyone’s eyes.
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Image used courtesy of Photon Bricks Project at the University of Nottingham shared under Creative Commons Attribution-ShareAlike (CC BY-SA) license
Morpho butterfly
Description:
The beautiful blue colour of the morpho butterfly is created by wave interference from nanoscale structures on its wings. The multiple reflections cause blue wavelengths of light to constructively interfere.
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Ultrasound transmitter and receiver
Description:
You can demonstrate various wave interference effects with a simple ultrasound transmitter and receiver kit which is cheap to build. Nick Mitchener has kindly written instructions of how to construct this which you can find here.
To operate this you will need to connect the transmitter to a signal generator at around 40 kHz and the receiver to an oscilloscope.
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Image used with permission of Nick Mitchener
Stationary/Standing waves
Simulation to show how stationary wave is formed
Description:
To teach the idea that a stationary wave is formed by two identical waves travelling in opposite directions interfering it is really helpful to have an animation showing two such waves and the resultant wave. This one from ophysics is excellent but there are lots of other options.
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Screenshot from ophysics.com. �Used on basis of general permission notice on the website:
Longitudinal Stationary/Standing waves on a slinky
Description:
Using a mini slinky stretched horizontally between a clamp stand and vibration generator you can create stationary/standing waves of a few Hz which are clear to see (especially in slowmo video). See IOP instructions below. I found that it worked only when the spring was in the air (not touching anything).
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Stationary waves in a narrow tank demo
Description:
It is possible with a bit of practice to create stationary waves in a narrow water tank (I found it easier to create the antinode in the middle and and both ends). However, the linked video is very good as it marks the nodes and antinodes so unless you have lots of time to practice then I would use this one as a video clip.
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Stationary/Standing wave in sound reflected from a board/wall
Description:
A stationary wave in sound can be created by pointing a loudspeaker connected to a signal generator at a wall or large piece of hardboard.�It is worth calculating an appropriate distance for the loudspeaker which should be at an antinode and the wall/board needs to be a node.
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Stationary waves on string practical
Description:
A vibration generator connected to a signal generator is used to vibrate a string and a stationary wave is created by adjusting the frequency. The length of string or tension in the string can easily be varied.
This is a fun variation for a demonstration where the mass per unit length changes part way along.
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Stationary waves sketching on mini whiteboards�and then producing a summary table
Description:
It is helpful to get students to sketch the fundamental and higher harmonics, calculate the wavelength in terms of string or pipe length and then use the wave equation to get an expression for frequency of the harmonic and compare to the fundamental. All this is best done initially on mini white boards to avoid concern over making mistakes. Then a summary table as illustrated on the right can be produced.
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Stationary waves on string simulation
Description:
This is a lovely simulation which shows stationary or standing waves on a string. You can choose from the fundamental to the 6th harmonic, adjust the finger position and amplitude and choose whether you want to hear the sound or not.
https://javalab.org/en/standing_waves_on_a_string_en/
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Screen shot used with permission from Javalab Standing Waves on Strings https://javalab.org/en/standing_waves_on_a_string_en/
Stationary/standing wave on a wire using �the motor effect and AC
Description:
A simple way to create a stationary/standing wave on a wire if you don’t have a vibration generator is using the motor effect. An AC current is passed through the wire between a pair of motor kit magnets and the length adjusted to get a clear stationary/standing wave pattern.
Using 50Hz low voltage AC, 30 swg constantan wire and a mass of 200g to tension will give a fundamental with a length wire of about 0.5 to 0.6m between the prism and clamp stand. Cut the wire about 1.2 m long.
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Stationary waves on venus
Description:
The Japanese Akatsuki Probe has detected a gigantic standing/statioanry wave in the atmosphere of Venus. The pressure wave extends over 10,000 km between the poles of the planet and is believed to be produced by surface winds colliding with the 4,500 m high Aphrodite Terra Mountain range near the planet’s equator (text used with permission of the IOP and Richard Brock from the Stories in Physics Booklet 4)
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Image or video
Processed using ultraviolet (365nm & 283nm) filtered images of Venus taken by Akatsuki on October 24 2018. JAXA/ISAS/DARTS/Kevin M. Gill Creative Commons Attribution 2.0 Generic
Transverse stationary waves on a rod / ruler
Description:
You can also excite transverse stationary waves in an aluminum rod (which you might have for a tall clamp stand). Support the rod at the nodes (22.4% of the length in from the ends - mark these on for easy reference) and then hit it in the middle on your leg as shown in the video.
You can also do the same thing in a metre ruler or cable trunking cover which has a much lower frequency which is also shown in the video.
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Longitudinal waves in aluminum rod
Description:
Hold a long aluminum rod at the exact centre. Put some violin rosin on your fingers and stroke the rod away from the centre. You should be able to excite the fundamental longitudinal stationary wave in the rod which is the same as the fundamental in an open-open pipe.
You can excite the next harmonic which is show in this video
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Speed of longitudinal waves in �aluminium rod with phyphox
Description:
Holding an aluminum rod in the centre and tapping the end with another metal object creates a longitudinal standing/stationary wave with an audible sound. Measuring the length of the rod and the frequency of sound with the phyphox app or similar allows the speed to quickly be calculated. An old tall aluminium clamp stand rod works well.
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Stationary waves on horizontal slinky
Description:
Demonstrate the fundamental and higher harmonics of a transverse stationary wave on a slinky by manually shaking the end of the slinky at the correct frequency. See the video for how this works.
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Image or video
Measuring the speed of light with stationary �waves with a microwave kit
Description:
A stationary wave can easily be created by pointing a microwave transmitter towards a metal sheet. The reflected wave interferes with the incident wave creating a stationary.standing wave. The position of the nodes and anitnodes can easily be found using a probe detector allowing the wavelength to be deduced, This can be combined with the frequency given in the specification to calculate the speed of light.
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Measuring speed of light with microwave oven
Description:
If the turntable is removed from a microwave oven you can find the position of the antinodes by seeing where a piece of chocolate/cheese melts first. You can also do this by colouring in a piece of paper with friction erasable pen (which disappears when it heats up).
From the spacing of the antinodes (½ a wavelength) you can deduce the wavelength and combine with the frequency of the microwaves to calculate the speed of light.
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Boomwhackers to show stationary waves in pipes
Description:
Good example of open-open pipes (wavelength of fundamental is twice the length of the pipe) or open-closed pipes if you add the octave caps which halves the frequency (wavelength of fundamental is 4 x the length of the length of the pipe). You can use as quick demo/practical or as a longer investigation.
Available from school suppliers and usual online retailers. Other similar products are available.
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Stationary waves in pipes animation
Description:
This animation https://ophysics.com/w10b.html is really nice for showing how the particles oscillate in air columns with stationary waves. There are lots of options about exactly what you can show.
Another alternative simulation: https://thephysicsaviary.com/Physics/Programs/Labs/ResonanceTubeLab/
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Screenshot from ophysics.com�Used on basis of general permission notice on the website:
Stationary waves and changing the speed of sound
Description:
An indigestion tablet is added to one of two bottles which were producing identical notes when blown over. The carbon dioxide produced lowers the speed of sound in the bottle and so the frequency of the note is reduced. A great next time question or thinking question for students.
Works better in reality than in the video. I like to prepare the bottles in advance with cling film over to keep carbon dioxide in it and then present the mystery as to why the bottles that look the same produce different notes.
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Stationary/standing waves and room modes
Description:
An entire room can be made into a stationary/standing wave. These have to be considered when designing rooms to have good acoustics. The video linked gives a brief introduction. If you have a decent loudspeaker and power signal generator you may be able to set up room stationary/standing waves - it is easier in smaller rooms.
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Rubens Tube
Description:
A great wow factor demonstration - a large diameter pipe has holes drilled every couple of centimetres. Gas flames are lit along the whole length. A stationary wave is formed using a loudspeaker at one end connected to a signal generator. The height of the waves shows the stationary wave formed. If you could the flames between nodes (and know the spacing of holes) you can deduce a half wavelength and use this together with the frequency from the signal generator to calculate the speed of sound in the gas ( higher than in air)
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Stationary wave with Kundt’s tube
Description:
In this demonstration a loudspeaker is attached to one end of long transparent pipe. The other end is blocked with a bung (or adjustable piston). Cork dust / styrofoam or polystyrene beads are spread along the whole length of the tube. A signal generator is connected to the loudspeaker and the frequency adjusted to form stationary waves. The cork dust or beads jump around a lot at the antinodes. Styrations also form.
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Measuring the speed of sound using a resonance tube �(loud speaker, microphone and oscilloscope)
Description:
A measuring cylinder is filled with varying volumes of water to vary the length of “a pipe” open at the top and closed at the bottom. A small loudspeaker is positioned at the mouth of the pipe and the frequency of sound is increased using a signal generator to the first frequency at which a noticeably louder sound is observed which corresponds to the fundamental stationary wave in the pipe. A microphone connected to an oscilloscope allows more accurate identification of the resonance. The speed of sound can then be calculated using the wave equation.
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Measuring the speed of sound resonance tube with tuning fork
Description:
A plastic tube is immersed in tall measuring cylinder of water so that the length of pipe that a stationary wave can form in can be adjusted by moving the tube up and down. A tuning fork is held over the mouth of the tube and the length is gradually increased until the sound of the tuning fork is clearly heard. The length of pipe will be a quarter wavelength and so that together with the tuning fork frequency can be used to calculate the speed of sound using the wave equation.
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Double slit / Two source interference
Two source interference in ripple tank
Description:
Using two point dippers you can create a two source interference pattern in a ripple tank. It is easier to see if your make a slowmo video.
This is much easier to show clearly if you have one of the modern ripple tanks which connects to a signal generator and in built strobe. This one is an example.
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Two source interference with sound
Description:
Connect two loudspeaker positioned about 1m apart to the same signal generator set at about 1500 Hz. Stand 1 m away from the speakers with your head at speaker height. Walk from side to side in front of the speakers with your hand covering the ear that faces away from the speakers and you can hear the points of constructive (loud) and destructive (quiet) interference.
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Two source interference with microwaves
Description:
A double slit for 2.8cm microwaves can be created using two wide metal sheets and a narrower one. A detector moved slowly across will move through areas of constructive and destructive interference.
Using audio frequency modulated microwaves and connecting the receiver to a loudspeaker allows students to hear the results.
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Simulations to understand Double slit with light
Description:
Two useful simulations to use when teaching Young double slit:
This one (shown on the right shows) wavefronts: https://javalab.org/en/youngs_double_slit_en/
Whereas this one shows waves and highlights the path difference: https://ophysics.com/l4.html
The phet one allows you to show sound waves as well as light and water ripples: https://phet.colorado.edu/en/simulation/wave-interference
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Two source interference 3D simulation
Description:
A lovely 3D simulation showing two source interference with waves along with photon arrivals. You can rotate it to view from any angle which makes it clear and engaging.
https://www.quantum-physics.polytechnique.fr/young.php?lang=1
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Emailed to ask permission to use a screenshot
Screen shot used with kind permission of Manuel Joffre
Young Double Slit Experiment with laser
Description:
The classic experiment is very simple to conduct with a laser. A slit separation of 0.1mm works well as a typical laser beam will easily cover both slits. Usual laser safety needed to ensure laser or reflections don’t go into anyone’s eyes.
It is instructive to show the effect of changing wavelength by shining different coloured lasers through the same slits. Follow the usual laser safety guidance.
Young is said to have developed his model for interference after observing the ripples generated by a pair of swans on Emmanuel College pond.
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Young Double Slit Additional Guidance
Further Guidance:
If you are short of equipment then the following suggestions may help:
See next slide for using travelling microscope and alternatives.
If you wish to show how the double slit pattern is covered by the single slit diffraction envelope then you can carefully adjust the position of the the laser so it changes between illuminating both slits and just one slit. See the video on the right which starts with the light on just one slit and moves onto both slits.
Measuring double slit separation with a travelling microscope
Description:
A travelling microscope is an ideal way to measure the slit separation if you have one. Move the crosshairs/wire from directly over one slit to directly over the other and find the difference between the two positions using the sliding vernier scale.
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Young double slit with white light
Description:
If you stick a double slit over a phone camera and view a filament lamp with a thin vertical filament you can see the fringe pattern from white light.
You can also insert red, green and blue colour filters to compare the fringe separation with different colours.
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Double slit OHP teaching model
Description:
A teaching aid model to let students see the effect of changing different variables in the young double slit experiment. Waves are printed onto OHP transparency film (yes you can still buy this). And then it is attached to the template using two paper fasteners. Students can then rotate the waves coming out of the two slits to see where they arrive in phase and constructively interfere and where they arrive in antiphase and destructively interfere.
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Diffraction gratings
Diffraction gratings basic demonstrations
Description:
When starting to look at diffraction gratings it is helpful to use some introductory demonstrations before later in the topic students complete their own practicals. I like to do the following:
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Diffraction grating diagrams and explanations
Description:
Before introducing the diffraction grating equation it is helpful to get students to explain what is creating the bright fringes and wide dark fringes.
You can give students some diagrams to annotate. The slides provide a lot of structure which may not be needed with more able students.
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Lines per mm traffic cone analogy
Description:
If students find it difficult to understand how to calculate the slit separation in a diffraction grating from the lines per mm then give them the traffic cone analogy.
Ask: “If there are 250 cones per km of road works what is the distance between the cones?”
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Image by Jack Gavin CC BY-SA 4.0 from Wikipedia
Diffraction grating simulations
Description:
There are lots of really useful simulations to use when teaching about diffraction gratings. Here are three of my favourites:
Shows the path difference: https://javalab.org/en/diffraction_grating_en/
Shows the beams: https://ophysics.com/l5b.html
Shows how spectra overlap: https://www.thephysicsaviary.com/Physics/Programs/Labs/EMSpectrum/
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Screen shot used with permission from Javalab Diffraction Grating: https://javalab.org/en/diffraction_grating_en/
Finding the wavelength of a laser using a diffraction grating
Description:
A standard A-Level practical for most exam boards. By measuring the diffraction
Works best using an 80 lines per mm diffraction grating as you will then get at least 5 orders which means you can analyse the results by plotting a graph of sinθ against n and the gradient of the graph will give you the wavelength over the slit spacing.
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Diffraction grating with white light
Description:
This demonstration is easiest to set up if you have an old slide projector which you can then project an image of a white slit onto the wall (You can also use an old OHP projector to make the image of the white slit). Then place the diffraction grating directly in front of the lens of the projector and you will have a beautiful spectrum.
As an alternative look through a diffraction grating at a filament lamp with a narrow filament (video here)
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Using smoke spray to reveal diffraction beams
Description:
In the same way as using smoke spray or a fine water mist spray to show a single laser beam you can show the diffraction beams by shining the laser through a diffraction grating and then through the smoke/water mist.
Nice to change between red and green laser. With difficulty you can also achieve the effect with white light as shown in the video on the right. Usual laser safety needed to ensure laser or reflections don’t go into anyone’s eyes.
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Measuring wavelength of LED (or infrared remote control)
Description:
An LED or remote control viewed through a diffraction grating with a ruler allow the angle of the fringe to be calculated with trigonometry and then the wavelength calculated.
You only need the mobile phone if you are trying it with an infrared remote control. If you are using an LED (see photos bottom right) you only need to look through the diffraction grating.
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Canadian Bank Note Diffraction
Description:
This is a very simple demonstration. Shine a laser through the maple leaf on a canadian bank note and the interference pattern created on a screen shows the value of the note.
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Bird feather diffraction gratings
Description:
This beautiful photograph by Andrew Fusek Peters makes a great next time question to ask when you have been studying diffraction gratings - why all the different colours from the sunlight passing through the feathers.
In fact James Gregory described using a bird feather to produce diffraction in a letter in 1673 which was one of the earliest reports of diffraction.
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Blue tit at dawn ©Andrew Fusek Peters used with kind permission
Other natural diffraction gratings
Description:
There are lots of examples of everyday objects behaving as diffraction gratings. Bird feathers are dealt with on the next slide.
The photographs show two examples a street light viewed through a net curtain (left) and a halogen spotlight reflected in an ipad mini screen. Both produce 2D diffraction grating patterns. The patterns on the James Webb Telescope images are another interesting example.
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CDs as diffraction gratings and estimating the track spacing
Description:
CDs act as reflection diffraction gratings. If you shine a laser onto the CD you can measure the fringe spacing and calculate the spacing of the tracks and estimate the data stored on the CD. This worksheet goes through it.
Note you need to be very careful to avoid reflections into anyones eyes as the laser points towards the CD and the interference pattern is reflected back towards the laser direction. I fix black sugar paper behind the CD to prevent any laser light going beyond the CD.
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Why reflection of CD looks different?
Description:
This is a lovely demonstration and/or next time thinking question. If you look at the colours produced by a CD acting as a reflection diffraction grating with a mirror behind it then the colours are different in the reflection to the direct view of the CD. The article linked below fully explains the effect but essentially you are viewing light from a different angle when looking at the reflected view of the CD.
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Role Model - Kathleen Lonsdale
Description:
Kathleen Lonsdale (1903-1971) was a Irish physicist and pioneer of X-ray crystallography, a friend of Dorothy Hodgkin and personally selected to work directly with William Bragg. She showed conclusively that the benzene ring was flat, something chemists had been arguing about for 60 years. She also went on to work on the synthesis of diamonds.
Text used with permission from OCR STEM contributors resource - link to resource below.
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Image Credit: FC Livingstone Smitsonian http://www.si.edu/copyright/