How Rainbows Form

To see a rainbow, you need to face away from the sun. That's not coincidence — it's physics.

What Happens Inside a Raindrop

When sunlight (white light) enters a raindrop, refraction occurs. Light slows down and changes direction as it moves from air into water.

The thing is, light isn't a single wavelength. Red light (long wavelength) bends a little, violet light (short wavelength) bends a lot. That's dispersion.

After reflecting off the inner wall of the raindrop and exiting again, another refraction occurs. The result: each color reaches our eyes at slightly different angles.

The Secret of 42 Degrees

Rainbows appear at about 42 degrees from the antisolar point. That's the optimal angle for reflected light from raindrops to reach an observer's eyes.

Every raindrop creates a rainbow, but we only see light from the drops positioned at exactly 42 degrees.

Double Rainbows

Sometimes you see two rainbows. The outer one results from light reflecting twice inside the raindrop. That's why its color order is reversed (inner: red→violet, outer: violet→red).