- When sunlight shines through water droplets in the air, it bends (refracts) and breaks into all the colours of the rainbow.
- A rainbow's full form is in the shape of a circle – we're just not normally in the right place to see it, so we see an arc.
- In a double rainbow, the order of the colours is always reversed in the bigger rainbow.
- Physical processes
- White light
5 things you didn't know
How are rainbows made?
1. Rainbows are made when sunlight shines through water droplets (e.g. rain) in the atmosphere – the white light is refracted (which means it bends) and separated into the colours of the rainbow.
2. Sir Isaac Newton discovered that white light (e.g. sunlight) is made up of seven main colours – red, orange, yellow, green, blue, indigo and violet. He used a beam of light and a triangular clear glass prism, and observed a phenomenon now known as refraction.
3. In very special circumstances, when sky conditions are just right, you can see a rainbow in the shape of a full circle.
4. When a double rainbow occurs, the larger rainbow is always fainter and has its colours reversed, which means the inside (rather than the outside) of the arc is red.
5. You don’t just get rainbows – moonbows occur when moonlight is separated by water droplets, and fogbows occur when the tiny water droplets inside fog form white rainbows!
Spark a discussion
- What happens to sunlight to make a rainbow appear?
- We might not be able to see it very often – but what shape is a rainbow's full form?
- What happens to the order of the colours in the rainbow when you see two together?