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Why are the colours of a rainbow always in the same order?

White lightWater dropletIt splits into coloursThe order never changes

The colours of a rainbow are always in the same order because each colour of light bends at a different angle inside a raindrop.

Sunlight looks like just one colour, but it is really hiding seven colours inside it. When light goes into a raindrop, it bends. This is called refraction. Then the light bounces back inside the drop, like a mirror, and bends again as it comes out.

Each colour of light has a different wavelength. Red has a long wavelength, and purple has a short one. Light with a short wavelength bends more, and light with a long wavelength bends less. So each colour comes out of the drop at a different angle.

Because of these different angles, the colours always line up in the same order: red at the top, and purple at the bottom. This order never changes, because light works the same way in every raindrop.

Quick facts

A rainbow has seven colours: red, orange, yellow, green, blue, indigo, and purple.
Sunlight bends as it enters a raindrop.
Each colour has a different wavelength, so each one bends at a different angle.
Red light bends the least, and purple light bends the most.
To see a rainbow, the sun must be behind us and the rain in front of us.
The colours are always in the same order because light works the same way in every drop.

Check what you remember

4 questions — all of them come from the quick facts above. There is no score and no wrong turn.

1. How many colours are in a rainbow?

2. What happens when light enters a raindrop?

3. Which colour bends the least?

4. Where must the sun be for us to see a rainbow?

Where this comes from

1 tr.wikipedia.org 85/100
Rainbow - Wikipedia
A trusted encyclopedia page that explains how rainbows form, with pictures.
2 nasa.gov 80/100
NASA
An official space agency site with scientific and accurate facts about light and sky events.
3 britannica.com 75/100
Rainbow | Britannica
A trusted encyclopedia page that explains the science behind rainbows.

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Bending Light

Light changes direction when it moves from one substance into another. This is called refraction. A raindrop is a different substance from air, so it bends the light.

🌈

White Light Is Really Colourful

Sunlight looks white to us, but it is really a mix of seven colours. When it passes through a prism, we can see each colour on its own.

📏

Wavelength

Every colour of light has a different wavelength. Red has a long wavelength, and purple has a short wavelength.

🪞

Bouncing Back

Light bounces once inside the raindrop and comes back out. This is called reflection. That is why we see a rainbow with our backs to the sun.

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