Adding Colors: An Optical Experiment

What You Need:

  • 3 flashlights
  • transparent plastic report covers (red, blue, and green)
  • a pair of scissors
  • adhesive tape

What You Do:

  1. Cut out a disk from each report cover about the size of the flashlight lens.
  2. Tape one disk over the clear lens of each flashlight. Aim the red beam at a nearby white wall. What color do you see?
  3. While the red remains on, aim the beam of blue so that it overlaps half of the red spot. What happens?
  4. Now aim the beam of green so that all three colors fall on the same spot. What happens as the colors are added to each other?

The Science

When light beams mix, the combined colors are added together. Unlike the mixing of paint pigments, this additive process produces lighter colors. When the right combination is produced, we "see" white.

Real-World Connection

The next time you're in a performance theater, take a look at the stage lights. Most likely, you'll see a row of lights that surround the stage. These border lights aren't white. Instead, they consist of a pattern of colored lights. When projected, these different colors create white.

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