ELI5: how rainbows are formed

A rainbow is formed when sunlight shines through raindrops in the air, which bend the light and split it into all its hidden colors.

Think of sunlight as a team of hidden colors traveling together. Even though the light from the sun looks clear or white, it is secretly made of red, orange, yellow, green, blue, indigo, and violet all mixed up.

To see how this works in everyday life, imagine playing in the yard on a hot summer day:

• Catching the light: When the sun shines right after it rains, the air is filled with millions of tiny, floating water drops. Each little raindrop acts like a tiny glass ball or a mini mirror.
• Bending the light: When a ray of sunlight enters a raindrop, the water slows it down and bends it. This bending is called refraction. Because each color bends at a slightly different angle, the colors start to separate.
• Bouncing the light: The separated colors hit the back of the raindrop and bounce back, like a rubber ball bouncing off a bedroom wall. This is called reflection.
• Showing the colors: As the light leaves the raindrop, it bends one more time and spreads out across the sky, pointing straight toward your eyes.

Whenever you see a rainbow, remember that the sun is behind you, the rain is in front of you, and millions of tiny raindrops are working together to paint a colorful picture in the sky.