How are rainbows made?

You ask: How rainbow made?

Need two thing for rainbow: sun behind Caveman, rain in front. Sunlight look white, but it hold all the colors hiding inside. Light dive into a round raindrop. As it enter, water bend it — light move about a quarter slower inside water than in air, and that slowing is what make it bend. And each color bend a little different amount. Light bounce off the back wall of the drop, come back out, bend again. Colors spread apart, like berries rolling to their own spots. Red bend least, blue bend most. Each drop send just one color to Caveman eye, at the just-right angle. Many many drops together paint the whole arc. Cave wisdom: rainbow not up in sky — it inside the water, and only Caveman eye at the right spot ever see it.