Cambridge Primary Checkpoint 0846 · Topic 9 of 10

Light and sound

How light travels, how we see, shadows, reflection and refraction, and how sounds are made and travel.

📌 Key points

Light travels in straight lines from a light source, such as the Sun, a fire or a lamp.
The Moon is not a light source. We see it because it reflects light from the Sun.
We see an object when light from it enters our eyes. Most objects reflect light from a source into our eyes.
A shadow forms when an opaque object blocks light. The closer the object is to the light source, the bigger its shadow.
Transparent materials let light through (clear glass), translucent materials let some through (tracing paper) and opaque materials let none through (wood).
Light reflects (bounces) off surfaces. Smooth, shiny surfaces like mirrors reflect light best. Refraction is light bending as it passes from one material into another.
Sounds are made when objects vibrate. The vibrations travel through solids, liquids and gases to our ears.
Sound cannot travel through a vacuum (empty space), so there is no sound in space.
Pitch is how high or low a sound is: faster vibrations make a higher pitch. Volume is how loud a sound is: bigger vibrations make a louder sound.

Light source: Something that gives out its own light, like the Sun.
Opaque: Does not let any light through.
Transparent: Lets light pass straight through, so you can see through it clearly.
Reflection: When light bounces off a surface.
Refraction: When light bends as it passes from one material into another.
Vibration: A quick movement backwards and forwards.
Pitch: How high or low a sound is.
Volume: How loud or quiet a sound is.

Explain how you hear a drum when it is hit, and why hitting it harder makes it louder.

Hitting the drum makes the drum skin vibrate.
The vibrating skin makes the air next to it vibrate, and the vibrations travel through the air.
The vibrations reach your ear, your eardrum vibrates, and your brain hears the sound.
Hitting harder makes bigger vibrations, so the sound is louder.

💡 Test tip

In sound answers, always mention vibrations. In light answers, remember that light travels in straight lines.

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