artificial colors to enhance the color differences. The colored shadow demonstration shows how a few colors can combine to make many colors or white, which is all colors combined.

Note: It is difficult to get a completely white screen with indoor/outdoor floodlights. The colors produced by them are not entirely monochromatic. Using much more expen-sive lamps produces a better white but the whiteness is not significantly enhanced. An alternative to the colored lamps is to obtain red, green, and blue theatrical gels (filters) and place them (one each) on the stage of three overhead projectors. Aiming each of the three projectors to the same place on

the screen produces the same effect as the lamps, but the colors are more intense.

For Further Research:

  • Look at color magazine pictures. How many colors do you see? Examine the pictures with a magnifying glass. How many colors do you see? Also examine the picture on a color television screen.
  • What common devices use red, green, and blue to produce colored pictures?
  • Is there any difference in the additive color process between using lights and using paints?
  • Punch a 2 cm hole in an opaque piece of paper. Adjusting the distance of the paper to the screen may help students investigate the color additive process.

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Last modified prior to September, 2000 by the Windows Team

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