Physics · Unit 7

Light and Sound

Seeing and hearing the world

Light and sound are grouped because both travel and both carry information, but they are fundamentally different: one is an electromagnetic wave that needs no medium, the other a pressure wave that cannot exist without one.

The unit covers how light travels, shadows and reflection, colour, how sound is produced, and pitch and volume.

This unit breaks down into 20 short steps and 119 questions, starting at difficulty 1 and building to 2. Below you can see exactly what it covers, how the path is structured, and worked examples with explanations.

Steps: 20
Questions: 119
Difficulty: 1-2

What this unit covers

Pitch and Volume
Colour and the Rainbow
How Sound Is Made
How Light Travels
Shadows and Reflection

Where this fits

An early unit. Waves and Sound and Light and Optics are the advanced treatments.

Where people slip

Sound needs a medium and light does not. That single difference explains why space is silent and not dark.

How the unit is structured

Light and Sound runs as 20 short steps that unlock in order. 15 are practice rounds and 5 are challenge rounds that pull together everything before them. Questions start at difficulty 1 and climb to 2 as you progress.

Step 1 · easierStep 20 · harder

Challenge rounds

Example questions

30 real questions from this unit, with the answer and the reason behind it, grouped by what they practise. There are 119 in the unit altogether.

Colour and the Rainbow

Fact or fibLevel 1
1. A rainbow forms when sunlight shines through raindrops.
Answer: True
Raindrops split sunlight into its colours, which is why rainbows appear when it is both rainy and sunny.
Fill the blankLevel 1
2. A glass ____ can split white light into all the colours of a rainbow.
- prismcorrect
- mirror
- window
- brick
A prism bends the different colours in white light by different amounts, spreading them into a rainbow.
Guess the numberLevel 1
3. How many colours are usually counted in a rainbow?
Answer: 7 colours
A rainbow is usually said to have 7 colours: red, orange, yellow, green, blue, indigo and violet.
Multiple choiceLevel 1
4. Why does fresh grass look green to us?
- It reflects green light and soaks up the other colourscorrect
- It makes its own green light
- It blocks all light
- It turns sunlight into water
Grass reflects green light back to our eyes and soaks up the other colours, so it looks green.
Picture questionLevel 1
5. 🌈 What do we call the band of colours that appears in the sky after rain?
- A rainbowcorrect
- A shadow
- A sunset
- A cloud
A rainbow appears when sunlight shines through tiny raindrops and splits into its colours.
Choose all that applyLevel 2
6. Which of these are the three primary colours of light?
- Redcorrect
- Greencorrect
- Bluecorrect
- Yellow
The primary colours of light are red, green and blue; mixing all three makes white light.

How Light Travels

Build the sentenceLevel 1
7. Build the sentence about what the Sun gives us.
Answer: The Sun gives us light and heat
The Sun sends both light and heat to Earth across empty space.
Fill the blankLevel 1
8. Light does not bend around corners. It travels in a straight ____.
- linecorrect
- curve
- circle
- corner
Light travels in straight lines, which is why it cannot bend around a corner to reach a hidden object.
Guess the numberLevel 1
9. Light is the fastest thing there is. About how fast does it travel through space?
Answer: 300000 km/s
Light travels at about 300,000 kilometres every second, faster than anything else in the universe.
Multiple choiceLevel 1
10. Which part of your body do you use to see the light from objects?
- Our eyescorrect
- Our ears
- Our nose
- Our feet
We see when light enters our eyes, so the eyes are the body parts we use for seeing.
Odd one outLevel 1
11. Three of these make their own light. Which one is NOT a source of light?
- A mirrorcorrect
- A candle
- A torch
- The Sun
A candle, a torch and the Sun all make their own light, but a mirror only bounces light that comes from somewhere else.
Choose all that applyLevel 2
12. Which statements about the image in a pinhole camera are correct?
- It is a real image that can fall on a screencorrect
- It is inverted (upside-down)correct
- It is always larger than the object
- It stays sharp even with a very large hole
A pinhole camera forms a real, inverted image; it is not always larger, and a huge hole would blur it.

How Sound Is Made

Fact or fibLevel 1
13. You could hear a loud explosion in outer space, just like on Earth.
Answer: False
There is no air in space to carry the vibrations, so sound cannot travel and you would hear nothing.
Fill the blankLevel 1
14. When you pluck a guitar string, it ____ quickly to make a sound.
- vibratescorrect
- freezes
- melts
- glows
A plucked string vibrates back and forth very fast, and that vibration makes the sound we hear.
Multiple choiceLevel 1
15. What does sound need in order to travel from one place to another?
- Something to travel through, like air or water
- A bright light
- A shadow
- A rainbow
Sound needs a material such as air, water or a solid to travel through, so it cannot move through empty space.
Picture questionLevel 1
16. 🥁 When you bang a drum, what actually makes the sound?
- The drum skin vibratingcorrect
- The colour of the drum
- The shadow of the drum
- The light from the drum
Hitting a drum makes its skin vibrate up and down, and those vibrations create the sound.
Guess the numberLevel 2
17. Roughly how fast does sound travel through air?
Answer: 340 m/s
Sound travels through air at about 340 m/s, far slower than light.
Match the pairsLevel 2
18. Match each instrument to the part that vibrates to make its sound.
Answer: Guitar = Vibrating string; Drum = Vibrating stretched skin; Flute = Vibrating air column; Xylophone = Vibrating wooden bar
Instruments make sound through resonating vibrations: a plucked string, a stretched drum skin, a column of air, or a struck bar.

Pitch and Volume

Fact or fibLevel 1
19. A guitar's thin strings make higher notes than its thick strings.
Answer: True
Thin strings vibrate faster than thick ones, so they make higher-pitched notes.
Fill the blankLevel 1
20. How high or low a sound is is described by its ____.
- pitchcorrect
- colour
- weight
- shadow
Pitch tells us how high or low a sound is, like a squeak being high and a rumble being low.
Match the pairsLevel 1
21. Match each kind of vibration to the sound it makes.
Answer: Fast vibrations = High pitch; Slow vibrations = Low pitch; Big vibrations = Loud sound; Small vibrations = Quiet sound
Fast vibrations make high sounds and slow ones make low sounds, while big vibrations are loud and small ones are quiet.
Build the sentenceLevel 2
22. Build the sentence that describes how the ear detects sound.
Answer: Sound waves make the eardrum vibrate
Sound waves entering the ear make the eardrum vibrate, and these vibrations are turned into signals for the brain.
Choose all that applyLevel 2
23. Which of these are real uses of ultrasound?
- Scanning an unborn baby in the wombcorrect
- Cleaning jewellery and surgical instrumentscorrect
- Detecting hidden cracks in metal partscorrect
- Lighting up a dark room
Ultrasound is used for prenatal scanning, cleaning delicate objects, and detecting cracks in metal; it cannot light a room.
Guess the numberLevel 2
24. What is the lowest frequency a healthy human ear can usually hear?
Answer: 20 Hz
Human hearing ranges from about 20 Hz at the low end up to about 20,000 Hz.

Shadows and Reflection

Choose all that applyLevel 1
25. Which of these can show you a reflection of your face? Pick all that work.
- A mirrorcorrect
- Still pond watercorrect
- Dry sand
- A wool blanket
Smooth, shiny surfaces like a mirror or still water reflect light clearly, but rough or dull things do not.
Fact or fibLevel 1
26. Shadows are longer when the Sun is low in the sky.
Answer: True
When the Sun is low, like in the early morning or evening, it casts long shadows across the ground.
Fill the blankLevel 1
27. A smooth, shiny mirror ____ light to make a clear picture of you.
- reflectscorrect
- blocks
- soaks up
- melts
A mirror reflects light back very evenly, so you can see a clear image of yourself in it.
Match the pairsLevel 1
28. Match each surface to what it does with light.
Answer: Mirror = Gives a clear reflection; White wall = Reflects light but no image; Black cloth = Soaks up most light; Clear glass = Lets light pass through
Shiny surfaces reflect light, dark surfaces soak it up, and clear surfaces let light pass straight through.
Multiple choiceLevel 1
29. A shadow is usually the same shape as what?
- The object blocking the lightcorrect
- The Sun
- The ground
- A rainbow
A shadow copies the shape of the object that blocks the light, so a ball makes a round shadow.
Guess the numberLevel 2
30. A ray of light hits a flat mirror at 35 degrees to the normal. At what angle to the normal does it reflect?
Answer: 35 degrees
By the law of reflection, the angle of reflection equals the angle of incidence, so it is 35 degrees.

Where these questions come from. Each unit starts as a plan of the concepts it should cover and the difficulty it should span. Questions are written against that plan with AI assistance, then checked by a validator that rejects anything without a single defensible answer, an explanation, or plausible wrong options. How we write questions sets out the whole process, and corrections are fixed in the bank and reach the site and the app the same day.

How you practise

This unit mixes 17 different question formats, so you are recalling and applying rather than recognising the same layout every time.

Build the sentence
Choose all that apply
Fact or fib
Fill the blank
Guess the number
Listen and choose
Match the pairs
Multiple choice
Odd one out
Picture question
Put in order
Sequence recall
Sort into groups
Spell it
Tap the pairs
True or false
Type the answer

Practise Light and Sound

119 questions across 20 steps. Start with step one and crawl at your own pace.

Play this unit

Read about Light and Sound

Explainers from our blog on what this unit covers. Each one ends with real questions from the bank.

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