Your children will like this simple experiment of refraction by only using these simple tools: a bowl, water, and a coin. Fill a half of the bowl with water. Put the coin into the water. Ask your children to step back until they can't see the coin over the lip of the bowl. Tell them not to move too far. Next, pour the water into the bowl until they can see the coin. Explain them that the coin is actually still on the bottom of the bowl. They can see it as the light bends when the coin's image passes through the air and water interface.
You can give them another simple experiment of light refraction. Take a pencil and a transparent glass of water. Ask your children to see both from above and the side of the glass. They will see that the pencil seemingly bends. Nevertheless, from the side of the glass, the pencil is still on the straight position. The bending pencil occurs due the refraction process between the air and water interface while it remains in real condition as the light passes through the flat glass surface.
Then they will be interested in how a rainbow can happen. You can give them simple experiment with a prism to create spectrum of colors. Prepare a flashlight, a prism, and a shoebox. Switch on the flashlight and put it into the shoebox. Make sure the box has slits that the light can come out. Then locate the prism in position to catch the light from the slit. Direct the prism to the wall. The prism will project the light and refract it twice into spectrum of colors.
Do these experiments as if you and your children were playing. It is because children prefer playing to studying. As they enjoy the experiments, they are actually studying.
