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Rainbows

Waves, sound and light · level 1, lesson 5 of 6

A question to start

The Sun's light looks white. But when the Sun shines through rain, a rainbow full of colours appears. Where do the colours come from?

The idea

Sunlight looks white, but it is really a mix of all the colours together. When sunlight passes through raindrops, the drops bend each colour by a slightly different amount, and the colours spread out. That is a rainbow.

The colours always come in the same order:

red, orange, yellow, green, blue, indigo, violet.

To see a rainbow, the Sun must be behind you and the rain in front of you.

red on the outside,violet on the inside

Worked examples

1. A garden hose. On a sunny day, stand with the Sun behind you and spray a fine mist. You can make your own rainbow.

2. A glass prism spreads sunlight into the same colours, in the same order.

3. Bubbles. The swirly colours on a soap bubble come from sunlight too.

Try it

  1. What colour is sunlight really made of?
  2. Name the colours of the rainbow in order.
  3. Where must the Sun be for you to see a rainbow?
  4. What colour is on the outside of a rainbow?
Answers
  1. A mix of all the colours.
  2. Red, orange, yellow, green, blue, indigo, violet.
  3. Behind you, with rain in front of you.
  4. Red.

Common mistake

"The raindrops are coloured." The raindrops are clear. The colours were in the sunlight all along; the drops only spread them out.

Where it leads