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Here are all the things you need to try this activity at home.

Basic Materials List

  • White surface: A white wall, white posterboard, or a large piece of white paper taped to a cardboard box works well. Do not use a beaded or metal slide projection screen.
  • Red, green and blue light bulbs or flood lamps, one of each color. Color compact fluorescent bulbs work well. In the video, we use 13-watt bulbs made by FEIT. Small, dimmer bulbs (such as clear-glass Christmas lights) are fine for tabletop use by a few students but for a large-group demonstration, bigger, brighter bulbs are better.
  • Three light sockets of any type, arranged so the light from the three bulbs is directed simultaneously towards the same area of the white surface.
  • A power source, such as the electrical socket strip shown in the video.
  • Any solid object such as a pencil, ruler, finger, etc.