You need three things to see a rainbow. You need bright sunlight and water drops in the air. And you must stand with the sun behind you.

Sunlight looks white. But it is made of all the colors of the rainbow mixed together.

Light bends when it goes from air into water. This bending is called refraction.

Light moves more slowly in water than in air. That is why it bends when it enters a raindrop.

Each raindrop acts a little like a tiny prism. It splits sunlight into its colors.

A rainbow shows up opposite the sun. So you must look away from the sun.

It can rain, and the sun can be low. If you see your own shadow, the rainbow circles around the shadow of your head.

The best chances come in the early morning or the late afternoon. The sun is low then. Rainbows often show up after a rain shower.

You can also see one in the spray from a hose or a waterfall.

A rainbow is really a full circle. The ground hides the lower part. From a plane you can sometimes see the whole circle.

Words to know

• refraction: light bending
• prism: color-splitting glass
• shadow: dark shape