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The pencil looked bent when you looked at it through the side of the glass, but when you looked from above and when you took it out of the water, of course it wasn't really bent! When light passes through the glass and water, it refracts, or bends. Since the light is being bent in different directions by the glass and the water, it hits your eye from different angles than normal and makes the pencil look bent! (The same thing happens when you dangle your legs into a swimming pool.) It also makes the pencil look bigger than it really is. As the light passes through the water, it bends in odd directions and magnifies the part of the pencil that is in the water. The more water between you and the pencil, the bigger the pencil will look. Try holding it right up to the side of the glass nearest you, and then move it to the other side and watch it grow!
Most of the time light looks white, but it is actually made up of colors: red, orange, yellow, green, blue, indigo, and violet. Those seven colors are the same ones you see in a rainbow! A prism is usually made of glass and is used to separate light into its colors. In this project, you can make your own prism to show the colors of light.
When the beam of light from your flashlight hits the outside of the glass, it bends slightly and breaks into its seven different colors. This bending is called refraction. The beam of light is separated into its different colors because each color bends at a slightly different angle. When the light comes out the other side of the glass, it is no longer a beam of white light. Instead, you see all the colors that make up white light in a rainbow shape on the white paper! This setup is a type of prism. A normal prism is a triangular piece of glass, but it works in the same way as the prism you just made.
A prism refracts light in almost the same way that raindrops refract sunlight to make a rainbow. The seven colors of the rainbow are called the visible colors of light. White light is made up of all of those colors, our eyes just can't see them until they are separated by water, glass, or something else. There are more colors of light, but our eyes can't detect them. Another way to see the rainbow colors of white light is to hold the back of a cd up to a light bulb. To see the colors even more clearly, poke a small hole in a piece of foil and cover a flashlight with the foil so the hole is in the middle, then shine it at the cd.
A rainbow should appear just above the spray of water from your hose when sunlight hits the water at the right angle. The water from the hose does the same things that rain does to make a real rainbow in the sky - it refracts the beams of sunlight so that they separate into their different colors. You can see the colors in the rainbow that appears above the water. The rainbow you made is much smaller than one you would see in the sky. Do you know why? It's because the water from your hose is only spraying in a small area. If there were more drops of water for the sunlight to hit, you would see a larger rainbow.