How is a rainbow created

How do I explain how a rainbow is created in a way that a toddler will understand the explanation?

It doesn't reflect (bounce off); it refracts (bends). You can see rainbows only when the sun is shining behind you and it is raining in front of you. Rainbows form when sunlight shines through millions of raindrops. Sunlight is a mixture of colours. When it passes through a raindrop, it is refracted (bent) and the light splits and spreads into seven colours.

Since children sometimes learn concepts like this by doing, here is a link to an experiment to make a rainbow. Have fun!
http://www.first-school.ws/activities/science/rainbow-experiment.htm

Tell them that the water in the sprinkler reflects the light of the sun, which is then split up into it's many parts. Say that sunlight is made up of every color imaginable, and the water splits up the sunlight so you can see the many colors that make up the sunlight. Hope that helps.

When sunshine hits the water drops just right it brings out all the colors in the water that we can't see at any other time.

It's like a surprise that you weren't expecting, so everyone goes out to take a look.

you can create a fake rainbow for him with a hose . put your finger on the hose and face it to the sun and colors will spread out like a rainbow and that is preety much what a rainbow is water and light.

good idea kcutie. Or say, sun meats rain and a rainbow is created.