How Does Light Make Colors?
Talk It Over
What color is light? What is a rainbow? Why do objects look different colors? How can we find out about different colors of light?
- Cellophane*: red, blue, and green
- 3 strong flashlights
- White paper
- Dark room
- Colored pencils or markers
- Cellophane in other colors
- Cut pieces of red, blue, and green cellophane big enough to cover the lights of the three flashlights. Tape the pieces in place—one color per flashlight.
- In a dark room, shine each of your lights on a white piece of paper. If the color looks too pale or the light beam too white, tape on another layer or two of cellophane. (Your goal is a brightly colored light, and cellophanes vary in their thickness and color intensity.)
- In a dark room, shine the three colors of light on the white paper so that they overlap, like this:
- Study the overlap areas carefully. Try holding the flashlights closer to the paper and then farther away. The overlap areas may be easier to observe if you back off.
- Make and color a drawing to record what you see. Be sure to show the individual colors plus what you see in all four areas of overlap. (Hint: The overlap areas are blue/red, red/green; green/blue, and blue/red/green.)
- Repeat the experiment with any other colors you want to test.
Stumbling around in dark rooms can be dangerous. Be sure to set up your experiment before you turn off the lights.
The "Go" procedure will work for you.
Natural light is white, but it contains all the colors. A prism breaks white light into its colors. You see those colors in a rainbow. Red objects look red because they absorb all the colors except red. They reflect (bounce) red light back to your eyes. In the same way, blue objects look blue because they absorb all the colors except blue. However, objects look their true color only in white light. Shine different colors of light on them, and their color changes. You can investigate how this works by shining colored lights on colored objects in a dark room and recording the colors they appear to be. Try to discover a rule that accurately predicts how the color of light and the color of an object interact.
Show Your Results
For "Go" and "Go Easy," display the diagrams that show your results. Write a few sentences to describe and explain what you observed.
For "Go Far," display—along with your drawings—some of the objects and colors of light you investigated. Report your observations and any "rule" you devised to explain them.
Tips and Tricks
- Juggling three flashlights at once can be tricky. Get a friend to help you hold the flashlights in the right places.
- Expand your project. Cut pieces of red, blue, and yellow translucent plastic* from the backs of report covers. Without looking at the sun, place the pieces on a bright window and move them around. Can you make the colors of the rainbow? Try to figure out why these results differ from what you observed with colored light.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.