Children zamazed and delighted by the results of this simple experiment to make your own rainbow. In addition, you will be teaching a memorable lesson on refraction, how light slows down and seems to bend when it hits water.
After it rains, when the light hits the tiny water droplets in the air, it slows down and bends. There is the arch of the rainbow. White light (sunlight) is made up of the 7 colors of the rainbow. When refraction occurs through air moisture it causes those colors to separate so that you can see them individually.
Fill your glass about 3/4 of the way with water.
Put the mirror in the glass while carefully trying to position it so it stays angled at the bottom, facing slightly upwards.
darken the room a bit and shine the flashlight on the mirror that is submerged in the glass.
Look around the room for your rainbow. Feel free to move the light which will cause the rainbow to shift. Allow the children to discuss their observations. Ask them to name the 7 colors of the rainbow (red, orange, yellow, green, blue, indigo, violet).
TL;DR (Too Long; Didn't Read)
When doing this experiment with children, allow them to do as many steps as possible on their own. This builds their self esteem, independence and love of learning.