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Sound

What is that sound?

Do Now

1.

8.

7.

6.

5.

4.

3.

2.

9.

10.

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  • What is sound?
  • Properties of sound wave
  • Describe different sounds
  • How do we hear sounds?
  • How do we use sounds?

Sound

What will you know?

Overview

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  • Be able to explain how vibrations make sound waves.
  • Be able to state the speed of sound in air.
  • Know about how sound travels in different mediums (gas, liquid, solid)
  • Describe the parts of a wave

Sound

By the end of the lesson, I should….

Learning Objectives

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  • pitch
  • amplitude
  • frequency
  • hertz
  • trough, crest, rest position (of wave)
  • decibels
  • deaf
  • oscilloscope
  • ultrasound
  • noise
  • wavelength
  • Vacuum
  • Rarefaction
  • ultrasound

Sound

Add definitions to your keywords as you go.

Keywords

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  1. Everything is made of particles
  2. Particles are attracted to each other
  3. Particles are always moving
  4. When heated, particles move faster

Sound

The 4 principles of the particle theory of matter are:

Starter

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  • Sound is a form of energy that travels as a longitudinal wave.
  • Sound is caused by vibrations.
  • Sound travels at 340m/s.
  • Sound travels fastest through solids because the particles are closer together

Sound

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There a 3 states of matter:

  • Solid
  • Liquid
  • Gas

Title: The Particle Theory

Before you start:

Use pencil

Particles should be the same size

Particles should not be too big or too small

Show what the particles are doing using arrows and lines

Sound

Draw a diagram with to show particles in each state of matter

Starter

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Sound

In your notebooks, write down as many kinds of waves that you can think of.

Do Now

Some you might have thought of �(and maybe some you didn’t…)

  • Seismic Waves (Earthquakes)
  • Light Waves
  • Sound Waves
  • Water Waves
  • Brain Waves

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Sound

What are the two types of waves?

Starter

  • Longitudinal Waves – motion of the particles is parallel to the motion of the wave.

  • Transverse Waves – motion of the particles is perpendicular to the motion of the wave.

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Sound

What is a transverse wave?

Task 1

Vocabulary:

A wave crest is where particle distance from its original position is a maximum.�

A wave trough is where particle distance is minimum.

Energy is moving perpendicular (forward) to particles (upwards).

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Rest position

Amplitude – the height of the wave. Measure from rest position to crest or trough

Wavelength – the distance from one crest to the next crest (or trough to next trough)

Sound

Describing a wave

Task 1

1

2

3

4

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Sound

Longitudinal Waves

Task 1

Vocabulary:

A rarefaction is where particle spacing is maximum�

A wave compression is where particle spacing is minimum.

motion of the particles is parallel to the motion of the wave.

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Vibrating objects move back and forth.

When it moves forward, gas particles get pushed together. This is called compression

Compression

(High density area)

Rarefaction

(Low density area)

Rarefaction

(Low density area)

Sound

When does a compression occur?

Task 2

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When the vibrating object moves away, the air particles can spread out again.

This is called rarefaction.

Compression

(High density area)

Rarefaction

(Low density area)

Sound

When does a rarefaction happen?

Task 2

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This happens quickly over and over again.

Compression

(High density area)

Rarefaction

(Low density area)

Rarefaction

(Low density area)

Compression

(High density area)

Sound

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See if you can create several compressions and rarefactions.

Sound

Modelling Sound Waves

Practical Task 2

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  • Sound is a form of ______ that travels as a ______________wave.

  • Sound is caused by __________.

  • Sound travels at _______________.

Sound

What do you know about sound?

Task 1

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A sound begins with a vibration

Sound

Make a vibration

Task 1

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We can produce these vibrations by :

          • Making a column of air vibrate,
          • plucking a string, or
          • by hitting an object

Sound

Find an object from your belongings to make a sound

Task 2

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We know that gas particles in the air are easily __________.

compressed

(squashed together)

Challenge: What does this have to do with sound waves?

Sound

Vibrations make waves

Task 2

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This shows sound waves carry energy!

Kinetic or potential?

Sound

A sound has moving particles

Demonstration

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Sound

In what direction can waves travel?

  • The best way to think about waves is as a disturbance that travels through a medium – some substance made of molecules.�
  • Because the particles always return to their original position, waves transfer energy without transferring matter.

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How do waves move?

Yes! Sound travels faster and further through a liquid than it does a gas.

Sound

Can sound waves travel through liquids?

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How do waves move?

Do you remember playing with these?

Your voice sends vibrations from one end to the other.

YES!

Sound

Can sound waves travel through solids?

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How do waves move?

Sooo Snnnneaky.

Snakes don’t have ear openings like we do, but can hear by sensing vibrations from the ground.

Sound

Snakes do not have ear openings

Did you know?

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How do waves move?

No!

WHY?

There are no particles in a vacuum.

Can sound waves travel through a vacuum?

Vacuumspace in which there is no matter or in which the pressure is so low that any particles in the space do not affect any processes being carried on there

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  • Through air 300 m/s
  • Through water 1500 m/s
  • Through iron 5000 m/s

WHY?

Think about the density of each state of matter.

Sound

How does the medium (state of matter) affect the speed of sound?

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Sound

Seeing and Visualising Waves

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?

How to perfect the drawing of a sound wave..

Starter

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  • Oscilloscope - An instrument that allows us to “see” and study sound waves.

What is an oscilloscope and what does it do?

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Rest position

Amplitude – the height of the wave. Measure from rest position to crest or trough

Wavelength – the distance from one crest to the next crest (or trough to next trough)

Sound

Describing a wave

Task 1

1

2

3

4

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Sound

What is pitch?

Pitch – the highness or lowness of a sound – is determined by the frequency of the sound.

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Loudness of a sound is determined by the amplitude – how far do the molecules move from their original position (size of the wave). �

Sound

What is loudness determined by?

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Sound

How does the wave effect the sound?

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Sound

Complete the worksheet

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Sound

What is Frequency?

We could also ask: How many cycles does this wave complete each second?

  • This quantity is called frequency – it is the number of cycles completed per unit time (usually per second). �
  • This is given the symbol ‘f’ and the standard units are Hertz (Hz). 1 Hz is 1 cycle per second (since cycle has no units, the units are actually just “per second” or s-1)�

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Sound

What is the time period?

We could ask: How long does it take for one complete repetition (or cycle)?

This is called period – the length of time that it takes for one full cycle to complete. It is usually given the symbol ‘T’ and is usually measured in seconds.

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Sound

Period and Frequency

 

The speed of a wave through an unchanging medium is constant

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  1. Water waves in a ripple tank are being created at a rate of 12 waves each second. Calculate the period of the water waves.

 

Sound

Period and Frequency worked example

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2) A singer hitting a high C has a period of about 1.91x10-3 s. Calculate the frequency of this note.

 

Sound

Period and Frequency worked example

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Sound

Period and Frequency

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Sound

The speed of sound through different mediums

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  •  

Sound

Calculating the speed of sound waves

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  •  

Sound

Examples.

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  •  

Sound

Examples.

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  •  

Sound

Examples.

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Example 1

  •  

Example 2

 

Sound

Worked Examples

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  •  

Sound

Worked Examples

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Amplitude measures how much energy is in the wave.

Big amplitude = BIG SOUND

Sound

How does amplitude effect sound?

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Sound

How does amplitude effect sound?

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Amplitude determines LOUDNESS!

An amplifier increases the amplitude of sounds.

Sound

What is loudness?

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  • Frequency – the number of waves per second.
  • Has the units of hertz, Hz

low frequency = low pitch

high frequency = high pitch

Long/large wavelength means…

Short/small wavelength means …

Wavelength and frequency

What is frequency

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The pitch depends on how many vibrations there are.

The more frequent the vibrations the higher the note.

The fewer the vibrations the lower the note

Sound

How does frequency affect sound?

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The higher the note, the more waves per second so the waves are squashed together.

The waves will have a short wave length.

Guess the sound

?

Sound

How does frequency affect sound?

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The lower the note, the FEWER waves per second so the waves are spread out.

The waves will have a longer wave length.

Sound

How does frequency affect sound?

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Mouse’s squeak: Low amplitude

High freq

Lion’s roar: High amplitude

Low freq

?

?

high or low?

?

?

Sound

Fill in the missing words

Checkpoint

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Sound

Summary

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  • When sound hits a medium that is more dense, most of the energy will reflect back, just like light. �
  • When we hear a reflected sound after hearing the original, we refer to it as an echo.

  • The reflection of sound is useful for many animals and technologies

Sound

What is an echo?

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The frequency range of humans is from 20Hz to 20,000Hz.

Below 20Hz are infrasounds, above 20,000 are ultrasounds.

Sound

What is hearing range?

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  • Ultrasounds are sounds that are too high (more than 20,000 Hz) for humans to hear.

Sound

What is ultrasound?

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  • Cleaning things

Sound

What are some uses of ultrasound?

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  • Scan pregnant women

Reflected ultrasound are sent detected and sent to a computer

Computer changes ultrasound signal into an image

Sound

What are some uses of ultrasound?

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Many uses of science have moral and ethical issues.

Sound

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  • Good
    • Gives first picture for family album
    • Gives parents early warning if twins...etc

  • Bad
    • Can tell gender of baby.
    • Parents may not want “the wrong” gender.

Sound

Ultrasound scans – Good or bad?

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Sound

Hearing and Deafness

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When a sound is made, the air around the sound vibrates.

Hearing starts when some of the sound waves funnel into the ear.

Sound

How do we hear?

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Sound

How do we hear?

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Sound

How do we hear?

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1. Ear flap (Pinna)

2. Ear canal

3. Ear drum

5. Anvil

6. Stirrup

7. Cochlea

4. Hammer

8. Eustachian tube

9. Auditory nerve

Sound

Parts of the ear

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Outer Ear - The earflap and the ear canal

Collects and directs the sound waves to the middle.

Sound waves go directly or get reflected into the auditory canal.

Ear wax in outer ear can stop sound waves from reaching the middle ear.

A human ear has 3 parts:

outer ear, middle ear, inner ear

Sound

Parts of the human ear

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Middle Ear – eardrums and 3 ear bones

Changes energy of sound waves into vibrations.

Sound waves reach eardrum and makes it vibrate.

The vibrations cause the hammer, anvil and stirrup (the three ear bones) to vibrate.

High energy waves from loud sounds can tear a hole in the eardrum

Sound

Parts of the human ear

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  • Sound becomes painful at about 130db
  • The eardrum breaks at 185db

OUCH!

Sound

Ouch

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Inner Ear – cochlea, Eustachian tube, auditory nerve

Changes vibrations into nerve impulses and send them to the brain.

Vibrations from ear bones travel through a liquid and to the cochlea.

Cochlea is lined with 20,000 tiny hair-like nerve cells.

Each nerve cell has different length and detects a different frequency of sound.

The tiny “hairs” are damaged by loud or constant noise. Be careful! Once you lose them, they never grow back!

Sound

Parts of the Human Ear

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Nerve cells on the hairs detect this movement.

They send signals to the brain.

You hear the sound.

Tiny hairs – cilia – hang down into the liquid. Vibrations travelling through the liquid push the hairs.

Sound

What are the tiny hairs in our cochlea?

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Sound waves are focused by the pinna and enter the ear canal.

The ear drum vibrates.

In the cochlea, vibrations are changed into electrical messages

The auditory nerve passes the electrical messages to the brain

The vibrations are passed on by the anvil, hammer and stirrup

We hear the sound.

Sound

Summary of how we hear

Activity – put these in the correct order

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1. Sound waves are focused by the pinna and enter the ear canal.

2. The ear drum vibrates.

4. In the cochlea, vibrations are changed into electrical messages

5. The auditory nerve passes the electrical messages to the brain

(Semi-circular canals are for balance)

3. The vibrations are passed on by the anvil, hammer and stirrup

6. We hear the sound.

Sound

Summary of how we hear

Activity – put these in the correct order

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What is this?

Why is it not good for this?

Sound

Hearing and Deafness

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The vuvezela is a horn that is popular at football matches in Africa. It creates a loud noise, but how loud?

Loudness is measured in decibels (dB)

faint

moderate

loud

very loud

painful

0

20

40

60

80

100

120

140

160

dB

whisper

alarm clock

lawnmower

chainsaw

conversation

jet engine

right next to the speakers at a rock concert

Where do you think those go on the decibel scale above?

a vuvezela

Sound

Hearing and Deafness

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  • Loudness is measured in decibels, dB

Any sound that is unwanted is called noise.

Sound

Decibel scale

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Sounds louder than 80 decibels are considered potentially dangerous.

Sound

Decibel scale

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Take care

of me!

X

Sound

Taking care of your ears

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Light and Reflection

Why do we see lightning before we hear thunder?

Do Now

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Light

What is light?

Starter

Light carries energy and travels as a wave.

Light waves travel in straight lines.

Light travels at a speed of 300,000,000 metres per second, which is much faster than the speed of sound.

Light is produced by the Sun, and by objects such as light bulbs and matches.

Summarise this in 5 words or less

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Light

How do we see things?

Task 1

An object that gives out light is described as luminous. How does light from a luminous object such as a light bulb reach the eye?

Light travels in a straight line directly into the eye.

LUMOS!

Make a list of 5 objects that are luminous

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Light

How do we see things?

An object that does not give out light is non-luminous. How does your eye see a non-luminous object such as a comb?

Light hits the comb and some of it is reflected into the eye.

Make a list of 5 objects that are non- luminous

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  1. Circle the luminous sources

  • Label the luminous sources

  • Draw how the one-armed man would be able to watch television.

  • Draw how the man would be able to see the chair.

Light

How do we see things?

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Light

How do we see things?

Light bulb

sun

TV

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  • 1. Light travels in _________________ lines
  • 2. Luminous objects ________________________ light
  • 3. The Sun is ________________________ because___________________________________________
  • 4. Light travels at _________________________ m/s
  • 5.Non-luminous objects ________________ the light into our eyes so we can see the object.

Light

Answer the following question in your books

Checkpoint

straight

give out

luminous

It gives out light

340

reflect

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Light

Are all objects the same?

Task 2

Opaque: no light will pass through

Transparent: all or most of the light passes through

Translucent: some light passes through

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  • An object that allows all light to pass through it is called………………………………………………

  • An object that allows just some light to pass through it is called…………………………………

  • An object that allows no light to pass through it is called………………………………………………
  • translucent transparent opaque

Leave some space under each one to draw something!

Light

Answer the following question in your books

Checkpoint

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1

2

3

  1. Transparent

  • Translucent

  • Opaque

Match 1 2 3 and A, B, C together!

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Transparent – these are materials which let all of the light straight through.

Translucent – these materials let light through but it is randomly scattered.

Opaque – these materials let no light through.

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clear glass

frosted glass

wood

wine glass

tracing paper

book

brick

cling film

steel

marble ball

pencil

curtains

cardboard

water

Light

Design a table to show whether these objects are transparent, translucent or opaque

Challenge: Can you think of any other objects for each category?

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Light

Why do you shadows form?

Task 3

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1 Which of these statements is true?

A Light travels in straight lines.

B Light is stopped when it meets a solid object.

C Light does not travel in straight lines.

D Light will only travel for about 2000km before it stops.

Light

Checkpoint

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2 Which of these is not a source of light?

A a light bulb

B the Sun

C a mirror

D a TV

Light

Checkpoint

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3 Shadows are formed because:

A light will only travel a certain distance before it stops.

B a substance called ‘darkness’ collects behind some objects.

C some objects do not give out light in all directions.

D light cannot go through some objects.

Light

Checkpoint

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4 Which statement is true?

A Sound travels faster than light.

B Sound will not travel. Only light can travel.

C Light travels faster than sound.

D Light and sound travel at the same speed.

Light

Checkpoint

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5 Objects that light can easily pass through are said to be:

A transparent.

B apparent.

C opaque.

D oblong.

Light

Checkpoint

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6 Which phrase best completes the following sentence? We see things because:

A they are luminous.

B the Sun shines on them.

C light from them enters our eyes.

D light from our eyes shines on them.

Light

Checkpoint

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7 Opaque objects can:

A transmit and reflect light.

B transmit and absorb light.

C reflect and absorb light.

D only reflect light.

Light

Checkpoint

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8 Which of these will absorb the most light?

A a white sheet of paper

B a sheet of clear glass

C a black piece of card

D an orange piece of card

Light

Checkpoint

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9. Which of these diagrams show how light rays travel?... There may be more than one that is right!

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ANSWERS

Light

Swap your books to mark each other’s answers.

Checkpoint

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1 Which of these statements is true?

A Light travels in straight lines.

B Light is stopped when it meets a solid object.

C Light does not travel in straight lines.

D Light will only travel for about 2000km before it stops.

Light

Swap your books to mark each other’s answers.

Checkpoint

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2 Which of these is not a source of light?

A a light bulb

B the Sun

C a mirror

D a TV

Light

Swap your books to mark each other’s answers.

Checkpoint

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3 Shadows are formed because:

A light will only travel a certain distance before it stops.

B a substance called ‘darkness’ collects behind some objects.

C some objects do not give out light in all directions.

D light cannot go through some objects.

Light

Swap your books to mark each other’s answers.

Checkpoint

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4 Which statement is true?

A Sound travels faster than light.

B Sound will not travel. Only light can travel.

C Light travels faster than sound.

D Light and sound travel at the same speed.

Light

Swap your books to mark each other’s answers.

Checkpoint

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5 Objects that light can easily pass through are said to be:

A transparent.

B apparent.

C opaque.

D oblong.

Light

Swap your books to mark each other’s answers.

Checkpoint

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6 Which phrase best completes the following sentence? We see things because:

A they are luminous.

B the Sun shines on them.

C light from them enters our eyes.

D light from our eyes shines on them.

Light

Swap your books to mark each other’s answers.

Checkpoint

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7 Opaque objects can:

A transmit and reflect light.

B transmit and absorb light.

C reflect and absorb light.

D only reflect light.

Light

Swap your books to mark each other’s answers.

Checkpoint

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8 Which of these will absorb the most light?

A a white sheet of paper

B a sheet of clear glass

C a black piece of card

D an orange piece of card

Light

Swap your books to mark each other’s answers.

Checkpoint

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9. Which of these diagrams show how light rays travel?... There may be more than one that is right!

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I still feel unsure. I need some more help to understand.

I feel ok. I need to do some more work to check my understanding.

I am happy and feel I understand and can explain the main points.

:

(

:

)

:

|

(L4) Describe how light travels from luminous sources.

(L5) Explain how we see both luminous and non-luminous light sources.

(L6) Use ray diagrams to show how we see both luminous and non-luminous objects.

Light

Are you now able to…

Checkpoint

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AMBULANCE

WE

ARE

LEARNING

ABOUT

REFLECTION

Reflection

Try and draw mirror images of the words:

Do Now

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Reflection

Can you decipher the hidden message?

Do Now

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Reflection

How could you explain why this is happening?

Starter

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Reflection

What types of reflection is there?

Task 1

Mirror

Specular

Diffuse

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  • About reflection?

  • About the image that is reflected?

  • Is the image real?

Why does the image in the reflection look the same?

Reflection

What does this tell us.....

Do Now

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  • Have smooth, shiny surfaces and are usually pale colours.
  • Give clear images because they reflect light regularly.

Reflection

What objects reflect light well?

Task 1

The Law of Reflection =  the angle of reflection is equal to the angle of incidence

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Reflection

Write the correct name for each number

Task 2

1.

2.

3.

4.

5.

6.

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Reflection

Reflection Experiment

Task 2

You will need:

    • Ray box
    • Slit
    • Paper
    • Protractor
    • Ruler
    • Mirror
    • Pencil

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Method

  1. Draw a mirror line on paper
  2. Add a normal line at 90° to the mirror
  3. Put the mirror on the paper and shine the ray at it.
  4. Use a pencil to mark the incident and reflected rays.
  5. Measure the angles between the incident and reflected rays.

Created by H Rogerson

normal

Incident ray

Reflected ray

Light

What is the method?

Task 2

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What happens when you do each of the following?

  • Move the box closer to the mirror?

  • Move the ray box further away from the mirror?

  • Shine the light straight down the normal line.

Light

Try this…

Task 2

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Conclusion

  • Use the following words and write your own conclusion to the experiment:

  • Angle, incidence, reflected, ray, normal, same

Created by H Rogerson

Light

Conclusion

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reflection, changing, normal, measuring, angle, perpendicular, light

I will find out what the relationship is between the _________ of incidence and the angle of _________________. I will do this by shining a ray of ___________ onto the mirror. I will then measure the angles on each side of the ______________ line using a protractor. The normal line is _________________ to the mirror. I will repeat the experiment by _____________ the size of the angle of incidence and ________________ the angle of reflection.

Reflection

Conclusion Support

Task 2

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Reflection

Answer the following questions in your books

Checkpoint

Just write the answers

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Light

True or False.

Checkpoint

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Reflection

How can we use reflection in the real world?

Task 3

The two plane mirrors must be positioned at 45° from the vertical. Light is reflected at right angles from the top mirror onto the bottom mirror and into the eye of the viewer.

How does a periscope use reflection?

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Reflection

How can we use reflection in the real world?

Task 3

Reflection can be very useful.

High-visibility strips are very reflective and make sure that this cyclist gets noticed when there is little light.

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Reflection

Captain Khan’s Tropical Treasure Hunt

Task 4

Ahoy there me harties! I have buried a hoard o’ treasure somewhere on this tropical island. Use this map and the laws of reflection to find the path.

Only those who listened to their science teacher will be loaded with gold (that’ll teach ya!) The landlubber who comes the closest shall receive the booty.

A word of warning to ya, only fools will climb the doom...

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Reflection

A teacher has a small torch. He switches it on and points it towards a mirror.

Exam Question

Exam question:

A ray of light from the torch reflects off the mirror. Use a ruler and protractor to draw the ray of light:

(i) from the torch to the mirror;

1 mark

(ii) reflecting off the mirror.

2 marks

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Refraction

Write the correct name for each number

Do Now

1.

2.

3.

4.

5.

6.

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1

2

3

  1. Transparent

  • Translucent

  • Opaque

Match 1 2 3 and A, B, C together!

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Transparent – these are materials which let all of the light straight through.

Translucent – these materials let light through but it is randomly scattered.

Opaque – these materials let no light through.

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Refraction

What is happening in each of the photos?

Starter

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Refraction

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  1. Draw a line around the glass block;

  • Draw a normal line, on one side of the glass, which is at a right angle to the surface of the block;

  • Use a ray box to shine a ray of light into the glass block, entering it at the normal line;

  • Mark the path of the ray of light through the block with two crosses;

  • Mark the position of the light leaving the glass block with two crosses,

  • Remove the glass block and draw a normal line at the point where the light exits;

7 Plot the path of the ray of light.

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Refraction

Investigating Refraction

Angle of incidence

i

Angle of refraction

r

Angle of emergence

e

i

r

e

glass block

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Refraction

In pairs you need to collect

Everything shown in this diagram plus a protractor!

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Refraction

I noticed that the ray of light is refracted (away from/towards) the normal when it goes into a glass block.

The ray of light is refracted (away from/towards) the normal when it comes out of a glass block.

The angle of incidence is (smaller than/equal to/larger than) the angle of emergence.

The angle of refraction is (smaller than/equal to/larger than) the angle of incidence.

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WHY did the light bend both as it went into the glass block and as it left the glass block?

Talk to the person next to you about this for 1 minute.

Refraction

Why was the light refracted?

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This is because glass is more dense than the air and it slows down the light.

The light ray bends away from the normal again when it travels into air which is less dense.

The light ray bends towards the normal when it enters the glass from the air.

Refraction

Why was the light refracted?

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Refraction

Why was the light refracted?

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Refraction

Can you now explain what is happening in each of these photos?

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This diagram shows what happens to light which is reflected by the pencil.

The light bends when it leaves the water.

Your brain thinks that light always travels in straight lines so the pencil tip seems to be nearer the surface than it really is.

Refraction

Can you now explain what is happening in each of these photos?

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  • Because of this bending, a fish in water looks nearer to the surface than it really is.

  • Aborigine hunters have trained themselves to correct for this when fishing so that they catch their tea successfully.

Refraction

Can you help Mr Trent catch the fish?

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1 The disappearing coin trick works by refraction.

a) Copy the two lower diagrams and complete the second one.

b) Explain how the trick works.

Refraction

Can you hide the coin?

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b) Explain how the trick works.

The water refracts the light rays coming from the coin.

Refraction

1. The disappearing coin trick works by refraction.

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When a pencil is put into a beaker of water it looks bent. This is because the light is refracted as it leaves the water. The light travels faster in air than water

slower reflected bent faster refracted

Choose three of these words to complete the sentences

Refraction

What happens to the pencil?

Plenary

1.

2..

3.

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Quiz!

Refraction

Quiz – Write your answers in your book

Plenary

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  1. Refraction is what happens when light:

A hits an opaque object.

B bounces off a mirror.

C is scattered by a rough surface.

D bends as it goes from one substance into another.

Refraction

Quiz – Write your answers in your book

Plenary

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  1. Refraction occurs because

A light speeds up when it meets a denser transparent material.

B light slows down when it meets a denser transparent material.

C light stops when it meets a denser transparent material.

D light reflects inside denser transparent materials.

Refraction

Quiz – Write your answers in your book

Plenary

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3 Which diagram shows the correct rays?

A

B

C

D

Refraction

Quiz – Write your answers in your book

Plenary

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  1. Where does refraction take place?

A in the centre of a transparent substance

B all the way through a transparent substance

C as light travels from one opaque substance into another

D as light travels from one transparent substance into another

Refraction

Quiz – Write your answers in your book

Plenary

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  1. Refraction is what happens when light:

A hits an opaque object.

B bounces off a mirror.

C is scattered by a rough surface.

D bends as it goes from one substance into another.

Refraction

Swap books – check your answers

Plenary

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  1. Refraction occurs because:

A light speeds up when it meets a denser transparent material.

B light slows down when it meets a denser transparent material.

C light stops when it meets a denser transparent material.

D light reflects inside denser transparent materials.

Refraction

Swap books – check your answers

Plenary

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  1. Which diagram shows the correct rays?

A

B

C

D

Refraction

Swap books – check your answers

Plenary

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  1. Where does refraction take place?

A in the centre of a transparent substance

B all the way through a transparent substance

C as light travels from one opaque substance into another

D as light travels from one transparent substance into another

Refraction

Swap books – check your answers

Plenary

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Refraction

Are you now able to…

Learning Objectives

I still feel unsure. I need some more help to understand.

I feel ok. I need to do some more work to check my understanding.

I am happy and feel I understand and can explain the main points.

:

(

:

)

:

|

(L3) Can state what happens to light as it hits glass at an angle.

(L4) Can describe how light bends towards or away from the normal when it changes medium.

(L5) Explain why refraction happens.

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This is because glass is more dense than the air and it slows down the light.

The light ray bends away from the normal again when it travels into air which is less dense.

The light ray bends towards the normal when it enters the glass from the air.

Dispersion

Why was the light refracted?

Do Now

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Dispersion

Explain how the trick works

Starter

The water refracts the light rays coming from the coin.

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Dispersion

What would life be like without colour?

Task 1

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Dispersion

Dull.

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Dispersion

Challenge: Can you make a rainbow using glass prism and white light?

Task 1

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Dispersion

Breaking up white light

You’ve just seen how a prism can break up white light into 7 colours.

This breaking up of white light is called dispersion. The prism disperses the light.

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Dispersion

This breaking up of white light is called dispersion. The prism disperses the light.

RED

ORANGE

YELLOW

GREEN

BLUE

INDIGO

VIOLET

top

bottom

When white light is broken up like this the 7 colours are always in the same order.

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Dispersion

Can you remember all 7?

ROY GBIV

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The shape of the prism means they spread out even more on leaving the prism.

You may see a small spectrum with a rectangular glass block but the colours do not spread out as much.

Dispersion

What is the spectrum?

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(L3) Recall that white light can be split to make a spectrum.

(L4/5) Describe and attempt to explain some effects of dispersion.

(L5) Explain why we classify some

colours as primary and secondary colours.

Why does light disperse like this?

The size of a wave is measured from one peak to the next and is called its wavelength.

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(L3) Recall that white light can be split to make a spectrum.

(L4/5) Describe and attempt to explain some effects of dispersion.

(L5) Explain why we classify some

colours as primary and secondary colours.

White light is made up of all the colours of the rainbow.

Each colour has its own wavelength.

Red has the longest and violet has the shortest wavelength.

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(L3) Recall that white light can be split to make a spectrum.

(L4/5) Describe and attempt to explain some effects of dispersion.

(L5) Explain why we classify some

colours as primary and secondary colours.

But the shorter wavelengths slow down most and so bend more sharply.

When light enters a glass prism it slows down.

Blue is a short wavelength.

Red is the longest one.

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(L3) Recall that white light can be split to make a spectrum.

(L4/5) Describe and attempt to explain some effects of dispersion.

(L5) Explain why we classify some

colours as primary and secondary colours.

As each wavelength, or colour, slows down at a different rate it therefore has a different angle of refraction to the rest.

This means the

different colours

spread out.

Blue Bends Best

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When a second prism is added ‘upside down’ the dispersion of the second prism is in the opposite direction to the original dispersion.

White light is formed again.

Dispersion

Can you recombine colours?

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Dispersion

Can you remember all 7?

ROY GBIV

Write 1-7 in your books

Write down the colour light (s) that will pass through the filter.

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Dispersion

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Dispersion

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Dispersion

Light vs Art

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Colours are made by mixing other colours of light.

There are three primary colours of light used to make all other colours. What are these colours?

red

green

blue

The three primary colours of light are red, green and blue.

magenta

The colours made by mixing two primary colours are called

the secondary colours – magenta, yellow and cyan.

Dispersion

Can you remember all 7?

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A red filter absorbs all colours…

A blue filter absorbs all colours…

A green filter absorbs all colours...

…apart from red light.

…apart from blue light.

…apart from green light.

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A magenta filter absorbs all colours…

A cyan filter absorbs all colours…

A yellow filter absorbs all colours...

…apart from red and blue.

…apart from green and blue.

…apart from red and green.

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A magenta filter absorbs all colours…

A cyan filter absorbs all colours…

A yellow filter absorbs all colours...

…apart from red and blue.

…apart from green and blue.

…apart from red and green.

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Filters let certain colours of light pass through, but absorb all other colours.

object

filter

1

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Filters let certain colours of light pass through, but absorb all other colours.

object

filter

2

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Filters let certain colours of light pass through, but absorb all other colours.

object

filter

3

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Filters let certain colours of light pass through, but absorb all other colours.

object

filter

4

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Filters let certain colours of light pass through, but absorb all other colours.

object

filter

4

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Filters let certain colours of light pass through, but absorb all other colours.

object

filter

5

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Filters let certain colours of light pass through, but absorb all other colours.

object

filter

6

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Filters let certain colours of light pass through, but absorb all other colours.

object

filter

7

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Dispersion

Learning Objectives

(L3) Recall that white light can be split to make a spectrum.

(L4/5) Describe and attempt to explain some effects of dispersion.

(L5) Explain why we classify some

colours as primary and secondary colours.

I still feel unsure. I need some more help to understand.

I feel ok. I need to do some more work to check my understanding.

I am happy and feel I understand and can explain the main points.

:

(

:

)

:

|

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  1. The range of colours in a rainbow is known as a ___________.
  2. A ___________ is formed when sunlight is dispersed off raindrops.
  3. White light passing through a prism is __________ into different colours.
  4. __________ light is dispersed the most by a glass prism.
  5. __________ light is dispersed the least by a glass prism.
  6. The bending of light is known as __________,
  7. A piece of apparatus which absorbs some colours of light but allows particular colours through is called a __________.
  8. When green light hits a blue filter, it is __________.
  9. A full moon ____________ sunlight, particularly __________ coloured light.
  10. A ________________ lens is thinner in the middle and fatter at both ends.

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Electromagnetic Spectrum

What is the speed of light?

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  • All the EM waves can be arranged according to their frequency or wavelength. The result looks like this:

Electromagnetic Spectrum

What is the electromagnetic spectrum?

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  • Radio waves have long wavelengths and very low energy, so they are useful for transmitting information for radio and television.�
  • Microwaves have a shorter wavelength and higher energy. They are used for satellite and telephone communications, as well as microwave ovens.�
  • Electrical appliances like remote controllers and intruder alarms use infrared waves.

  • X-Rays are used for medicine and in security scanners, since they can penetrate light materials like fabric and skin (higher energy).

Electromagnetic Spectrum

Uses of EM ways

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  • Because X-rays can penetrate your skin, there is a chance that they can harm the cells in your body.

  • This is why you will typically be protected with a lead vest when you visit the doctor or dentist

Electromagnetic Spectrum

Safety – X-rays

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  • Since microwaves have much lower energy than X-rays, lead protection is not necessary.�
  • They typically do not have enough energy to penetrate the skin, but extended exposure is not recommended.

Electromagnetic Spectrum

Safety Microwaves

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  • Ultraviolet radiation has much more energy than microwave, and can damage skin cells with sufficient exposure. �
  • Wearing sunscreen, hats, and long clothing can prevent this, and polarized sunglasses to protect your eyes are recommended.

  • NOTE: UV radiation does not get absorbed by clouds, so you can still get burnt on a cloudy day!

Electromagnetic Spectrum

Safety - UV