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Name: Susan T.
Status: student
Age: 12
Location: N/A
Country: N/A
Date: 3/7/2003
Question:
How does a prism turn ordinary light into a spectrum of colors?

Replies:
Susan,

Ordinary white light is really made up of all the different colors combined together. When the white light goes through the prism, each color bends to a different angle. The prism separates the white light into all the different colors that it is made of.

An interesting experiment can be done with three flashlights and colored plastic you can see through. Cover one flashlight with red plastic. Cover one with green plastic. Cover the third with blue plastic. In the dark, shine them on a white piece of paper or a white wall. You will see a red spot, a green spot, and a blue spot. Now, shine all three on the same place at the same time. Make their spots overlap. You will se a much whiter light than any of the three spots alone.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College

Hi Susan,

Very cool question. A prism is a piece of glass that refracts or ends light. Light that we see everyday is called white light. You may already know that white light contains all the colors of the rainbow. When white light passes through a prism, each color of light bends at a slightly different speed. When this happens the colors become spread out enough that we can see a rainbow. Violet light is bent the most and red is bent the least.

Happy science!

Martha Croll

"Ordinary" white light is actually a mixture of light of all visible wavelengths, that is, colors. When light moves from air to glass and back to air again, it changes direction slightly with each change in material. Going from air to glass, blue light bends the most and red bends the least. So the rays of light of different colors that were all going the same direction move in slightly different directions, and the spectrum of colors results.

Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois


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