Science
How does a rainbow form?
A rainbow forms when sunlight passes through raindrops, which bend and split the light into its colors. Each droplet acts like a tiny prism, separating white light into red, orange, yellow, green, blue, and violet, and reflecting them back to your eyes.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a rainbow works.
Step by step
- 1Sunlight enters a raindrop and bends (refracts).
- 2Different colors bend by slightly different amounts, spreading them out.
- 3The light reflects off the back of the drop and exits, split into colors.
- 4You see a rainbow with the sun behind you and rain ahead.
- 5It's always a circle, though the ground usually hides the lower half.
Frequently asked questions
- Why does a rainbow have colors?
- White sunlight is a mix of colors; a raindrop bends each color by a slightly different amount, fanning them out into the visible spectrum.
- Why do you need the sun behind you to see a rainbow?
- The drops reflect sunlight back toward its source, so you see the bow when the sun is behind you and the rain is in front.
- Are rainbows actually circular?
- Yes — a rainbow is a full circle of light, but the horizon usually blocks the bottom; from a plane you can sometimes see the whole ring.