How Do Rainbows Form

A rainbow is one of nature's most colorful shows. It appears when sunlight shines through millions of tiny raindrops. Each raindrop acts like a tiny prism. The raindrop bends the white sunlight and splits it into the different colors we see. Red is always on the outside and violet is on the inside.

Inside a Raindrop

When a beam of sunlight enters a raindrop, it slows down and bends. This bending is called refraction. The light bounces off the back of the raindrop like a mirror. As it leaves the raindrop, it bends again. Each color of light bends at a slightly different angle, so the colors spread out.

Seeing a Rainbow

To see a rainbow, the Sun must be behind you and rain must be in front of you. The light enters the raindrops, bounces around inside, and comes back toward your eyes. You need to be at just the right angle, about 42 degrees from the sunlight. That is why rainbows appear as an arc in the sky.

Fun Facts

• No two people see exactly the same rainbow because each person is at a different angle.
• Rainbows can form in fog, mist, spray from waterfalls, and even in your garden hose.
• A moonbow is a rainbow made by moonlight instead of sunlight. It is very faint.

Did You Know?

A rainbow is actually a full circle, but you can only see the top half because the ground is in the way. From an airplane or a tall mountain, you can sometimes see a complete circular rainbow!