Light and colour

Ages 9 to 12 Read alone or together · about 30 minutes

Read together

Light travels in straight lines. When it meets something, it can be reflected, absorbed or pass through.

White sunlight is a mix of all colours. A glass prism or raindrops can split it into a rainbow, because each colour bends a little differently. Isaac Newton showed this with prisms in the 1660s.

We see an object as a colour because it reflects that colour of light and absorbs the others.

Do it

1. On a sunny day, fill a clear glass with water and stand it on a table near a window, with a white paper on the floor. Move the glass until a small rainbow appears. Never look at the sun.
2. Shine a torch through a CD or a clear glass prism onto a wall. What colours do you see, and in what order?
3. Put a mirror on a table and use a torch to reflect light onto a wall. How does the angle change?
4. Look at red, green and blue objects through a piece of coloured plastic. What changes?

Talk about it

• Why does a rainbow appear after rain?
• Why does a red apple look red?

For the grown-up

White light splits into colours when it is bent, or refracted, by water or glass. In a rainbow, sunlight is refracted and reflected inside raindrops. The Bible's rainbow in Genesis 9 is a sign of promise. Keep children from looking at the sun, and do not use laser pointers.

Mark as done

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Where this comes from

• NGSS Lead States, Next Generation Science Standards: For States, By States (National Academies Press, 2013), performance expectation 4-PS4-2 (develop a model to describe that light reflecting from objects and entering the eye allows objects to be seen)
• Isaac Newton, Opticks (1704), on the splitting of white light by prisms
• National Aeronautics and Space Administration (NASA), Science, on light, rainbows and the electromagnetic spectrum

Written with AI assistance and checked against the sources listed. Please read it before sharing it with a child.