How are rainbows made?
Quick answer from Eartha
Rainbows happen when sunlight meets raindrops still floating in the air. Each raindrop acts like a tiny prism, bending the sunlight and splitting it into all its colours. The light bounces inside the droplet and comes back out, spreading into a curved band of red, orange, yellow, green, blue and purple.
The longer story
A rainbow needs two things at once: sunshine and raindrops. That's why you often spot one right after a shower, with the sun peeking out behind you.
When sunlight hits a raindrop, it slows down and bends as it goes in. This bending splits the white sunlight into all the colours hiding inside it, a bit like a tiny glass prism.
The light bounces off the inside back of the droplet like a mirror, then bends again as it exits. Millions of droplets do this at once, each sending out one colour towards your eyes.
Because every colour bends by a slightly different amount, they line up in the same order every time: red on the outside, then orange, yellow, green, blue and purple. You always see a rainbow with the sun behind you and rain in front.
Try this at home: make an indoor rainbow
- Stand with your back to the sun, holding a garden hose or spray bottle on the mist setting.
- Spray a fine mist of water into the air in front of you.
- Look for a rainbow appearing in the mist.
Words to know
- prism
- Something that bends light and splits it into colours.
- refract
- To bend as light moves from one material into another, like air into water.
- spectrum
- The full range of colours hidden inside sunlight.
For grown-ups: what is my child learning here?
Age band: Ages 5-8
Curriculum link: Australian Curriculum v9 Science, Year 3 to Year 4, Physical Sciences strand: exploring how light behaves, including reflecting and bending.
The concept: The child is learning that white light contains many colours that can be separated by water droplets.
More classroom ideas are on our teachers page, and safety notes for families are on for parents.
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