Topic 8P3: Waves
States of matter (solids, liquids and gases)
If something has energy what does that mean?
nuclear
Energy can be transferred in 4 ways
mechanically
electrically
heating by particles
by radiation
Year 7 Waves and Year 8 Energy Recall
Answer as many of the questions on page 66 as you can.
Check and improve your answers as we go through the next few slides.
Water waves travel�
������through moving particles.
Sound waves travel�������through moving particles���
Light waves travel�������through moving waves of energy��
Check your answers
energy
information
matter
perpendicular
parallel
✔
✔
How could you use an echo to work out the speed of sound?
3
5
2
1
4
Parts of a wave
Top of the wave.
Bottom of the wave.
How tall the wave is.
Distance between wave tops
Crest
Trough
Amplitude
Wavelength
How many waves there are
Frequency
Sound waves
Topic 8P3: Waves
What do you think happens to the light as it hits the three surfaces?
Copy the arrows showing the incident rays onto the diagrams on page 69 and then draw what you think will happen to one arrow for each of the materials.
Carefully watch the demonstration to show how to set up a ray box and shine a light from it.
Remember to take care not to leave the ray box on for too long as it can get very hot.
Set the power pack at 9v.
Practical – page 70
transmitted
(like through a window)
Light waves can be:
reflected
(like in a mirror)
absorbed
(like by blackout curtains)
refracted
(like in a glass of water)
Refraction is also what happens to light as it passes through a camera lens or the lens in your eye.
Answer the questions on page 71
2. What happens to light when it strikes the mirror?
1. What is the difference in the way in which light travels through normal glass and through frosted glass? Draw diagrams to help explain your answer.
3. What happens to light when it interacts with the camera lens?
2. What happens to light when it strikes the mirror?
1. What is the difference in the way in which light travels through normal glass and through frosted glass? Draw diagrams to help explain your answer.
3. What happens to light when it interacts with the camera lens?
2. What happens to light when it strikes the mirror?
3. What happens to light when it interacts with the camera lens?
Topic 8P3: Waves
Sound waves travel through moving particles����������
Water waves travel through moving particles.
Light waves travel through moving waves of energy��
The differences between sound and light
Answer the questions on page 72 after watching the demo.
Answer these questions on page 73.
Then, read the phrases in the box at the bottom of the page and decide whether each is true for water waves, light waves and sound waves.
Complete the Venn diagram on page 74 using the phrases in the box at the bottom of page 73
Topic 8P3: Waves
Reflection in a Mirror
Normal - a dashed line that is 90° (right angles, perpendicular) to the mirror
Incident light - this is the light that falls on the mirror
Angle of incidence - the angle that the incident falls at
Reflected light - the light that is reflected by the mirror
Angle of reflection - the angle the light is reflected at
Both angle are always measured between the ray of light and the normal
The Law of Reflection
Complete the gap-fill sentences at the bottom of page 75.
Practical investigation into reflection
You will be investigating the relationship between the angle of incidence and the angle of reflection of light in a plane mirror.
Independent Variable:
(which variable are you changing?)
Dependent Variable:
(which variable are you measuring?)
Control Variables:
(which variables are you keeping the same?)
Reflection Practical
Collect the following equipment:
Reflection Practical
Results table
Angle of Incidence | Angle of Reflection |
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You are in the dark in the cupboard under the stairs with your cat. �There is a mirror on the wall�What can you see after 10 minutes in the dark?
A | You can see everything, but it is very dim. |
B | You can only see the cat’s eyes. They are shining. |
C | You can only see the mirror. It is shining dimly. |
D | You can’t see anything at all. |
A | 1, 2 and 3 |
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|
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B | 1 and 3 only |
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C | 1 only |
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D | 3 only |
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Spotting light
John has lost his pet cat in the dark.
He uses a torch to find it in his garden. Where is there light?
Put a tick (✔) in the box next to the best answer.
Seeing a luminous object
A luminous object gives out light and can also be called a light source.
Light travels in a straight line directly into your eye.
How does light from a light bulb and other light sources reach your eye?
13/02/2025
Objects that do not give out light are non-luminous.
Light from the light source strikes the book and some of the light is reflected into your eye.
1 | Light travels out in all directions from the Sun. | |||
2 | Sunlight passes through the window into the room. | |||
3 | Some light from the Sun falls on the book | Some light from the Sun goes into my eyes. | Sunlight fills the room and makes it bright. | |
4 | Light is given out by the book. | Light is scattered by the book. | Light is soaked up by the book. | |
5 | As a result, some light travels from the book to my eyes | At the same time, some light goes from my eyes to the book. | ||
6 | I see the book because it is lit up. | I see the book because this light enters my eyes. | ||
Seeing an explanation
Imagine you are in a room.
It is lit by sunlight and you are
looking at a book on the table.
How do you see the book?
Page 77 - pick one statement in each row to explain how – put a line through the others.
Seeing an explanation
Light travels out in all directions from the Sun.
How do you see the book? Pick one statement in each row to explain how.
1
2
3
4
5
Some light from the Sun falls on the book
Some light from the Sun goes into my eyes.
Sunlight fills the room and makes it bright.
As a result, some light travels from the book to my eyes
At the same time, some light goes from my eyes to the book.
Sunlight passes through the window into the room.
Light is emitted by the book.
Light is scattered by the book.
Light is absorbed by the book.
I see the book because it is lit up.
I see the book because this light enters my eyes.
6
Some light from the Sun falls on the book
Light is scattered by the book.
As a result, some light travels from the book to my eyes
I see the book because this light enters my eyes.
Sunlight passes through the window into the room.
Light travels out in all directions from the Sun.
Mirror reflection
How can you describe Harry’s reflection?
A
Harry’s reflection is on the mirror
B
Harry’s reflection looks back to front
C
Harry’s reflection is the same size as Harry
D
Everyone looking at the mirror sees the same reflection that Harry sees
I am sure this is right
I think this is right
I think this is wrong
I am sure this is wrong
Mirror writing
What can you say about the reflection?
A
The mirror turns the reflection round
B
The mirror reflects back what is in front of it
C
Looking through the back of the writing, we see the same as the reflection
I am sure this is right
I think this is right
I think this is wrong
I am sure this is wrong
Behind the mirror
Why does the reflection look as if it is behind the mirror?
What is the best reason?
A
The object’s image bounces (reflects) off the mirror
B
The object’s image reflects off the mirror at an equal angle
C
Light appears to come from an object behind the mirror
D
The mirror makes an image of what is in front of it
Object
The reflection looks as if it is here
How can you see the ball reflected in a mirror?
object
reflection
Drawing a reflection
Draw ray diagrams to show how these objects are reflected in a mirror.
Object
Reflection
1
Object
2
Object
3
Two eyes looking
Object
4
Two ends of an object
Object
3
Two eyes looking
Drawing a reflection
Draw ray diagrams to show how these objects are reflected in a mirror.
Object
Reflection
1
Object
4
Two ends of an object
Object
2
Reflection
Reflection
Reflection
Topic 8P3: Waves
Colours practical
Person 1 - Collect 2 ray boxes, a ray box board, a red, a green and a blue filter.
Person 2 – Collect a power pack
Set the power pack to 6V (increase the voltage if you need a brighter light) and check the ray box works.
Shine light through the filters as shown on page 80 and fill in the blanks beside the diagrams – hold a white page up to see the best results.
Answer the question at the bottom of the page.
Complete the practical, fill in the gaps and then answer the question at the bottom of page 80.
Filtering White Light
67
Red light
White light
Absorption of visible light
White (!) light is actually made of different colours of light.
When light passes through a coloured filter, some colours (wavelengths) of light get absorbed.
Complete the top table on page 81.
If you were mixing paint, this is what happens:
But, mixing light is different, lets see what happens.
Follow the instructions at the top of page 82.
Mixing colours
70
Green
Yellow
Cyan
White
Red
Magenta
Blue
Colours of light | Colour in overlap |
red + blue | |
blue + green | |
red + green | |
red + blue + green | |
Electromagnetic / EM radiation��.... is caused by a disturbance in electric and magnetic fields�.... it travels at 300 000 000 m/s in a vacuum �.... differences in wavelength causes different types of EM radiation
The electromagnetic spectrum
The visible light spectrum
.... is the part of the em spectrum visible to the human eye.
740 – 625 625 – 590 590 – 565 565 – 520 520 – 300 500 – 435 435 – 380
Wavelength (nanometers)
Seeing colour
Seeing colour
Seeing colour
Seeing colour
Seeing colour
Seeing colour
Complete the bottom table on page 81.
81
Red
Black
Black
Black
Blue
Black
Black
Black
Green
Red
Blue
Black
Tick or change your answers as we go through them
Answer the questions on page 83
The final question....
Explain what happens to the temperature of objects in terms of the energy transferred by light.....
The more light an object absorbs the higher its temperature.
Topic 8P3: Waves
Ripples occur in 2 ponds.
What could I measure to know the differences between the waves?
Because waves are repetitions of oscillations we can plot some of this information like a graph...
Top of the wave.
Bottom of the wave.
Size of the gap between 2 waves
How many waves pass a point every second
Rest position.
Height of the wave from rest to top or bottom
amplitude
rest position
wavelength
wave speed
period
frequency
crest
trough
Top of the wave.
Bottom of the wave.
Size of the gap between 2 waves
How many waves pass a point every second
Rest position.
Height of the wave from rest to top or bottom
Copy these labels onto the diagram on page 84
Which wave has the smallest amplitude?
1/8
Which wave has the largest wavelength?
Which wave has the highest frequency?
How many waves are shown in this diagram?
2
4
8
16
If it took one second to produce these two wavelengths, what is the frequency of the wave?
2 Hz
1 Hz
0.5 Hz
16 Hz
1 s
What is the amplitude of this wave?
0 cm
12 cm
10 cm
5 cm
Answer the questions on pages 85 - 87