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Finding Color In Light!

Light is the part of the electromagnetic spectrum. It usually travels through space as electromagnetic waves. Light can be seen, while many other waves of the electromagnetic spectrum cannot be seen. The electromagnetic spectrum includes radio waves, infrared rays, visible light, ultraviolet rays, x-rays and gamma rays.

Often, people think of light as being the typical white light that is seen. White light is made up of many different colors. In fact, when you see a rainbow, the colors displayed are those that make up the visible spectrum. Have you ever heard the acronym ROY-G-BIV? It stands for the colors that make up the visible spectrum or the colors that we see including: Red, Orange, Yellow, Green, Blue, Indigo, and Violet. Each color of light has a different wavelength. Our eyes respond to the different wavelengths (frequencies) by seeing the different colors. Did you know that the color you see is the color being reflected and all other colors are being absorbed by the object?



  • Small empty baby food jar
  • Empty can
  • White paper
  • Water
  • Directional light source (such as a bright flashlight)
Safety concerns: icon Be sure to keep all glassware, eye, electrical, and chemical safety rules. As with all science lab activities, the most important safety rule is to follow all teacher directions.



  1. Set the can at one end of the white paper.
  2. Set the baby food jar on top of the can.
  3. Direct the light source across the top of the jar at a sharp angle so the shadow from the can falls across the paper.
  4. Fill the jar with water until it brims above the lip.
    • The rounded edge of the water should refract a spectrum of color onto the shadow part of the white paper.


  1. List the colors as you see them. (If you did this correctly, you should see six different colors.)
  2. Place the colors in order of decreasing wavelength (hint: red light has the longest wavelength.)
  3. What differences in observation did you notice as you added water to the jar?
  4. What do you think would happen if you tried to grow a plant using only one color of light? Example: Only shine green light on the plant.


  • Use the previous experiment as your control and now introduce new variables.
  • You might try the following:
    • A different light source (perhaps using a mirror to direct sunlight or an over head projector.)
    • Use different colors of Saran Wrap® over a flashlight or use colored light bulbs.

Review Science safetey rules here.

Get the plug-ins: Get Adobe Acrobat Reader , and Get Quicktime Player. (The QuickTime plug-in is needed to play sounds and movies correctly.)

Want to share photos of you or your friends doing this activity? Send it in an e-mail with the following information:

  1. The title of the activity
  2. The URL (Internet address)
  3. Your name.

Remember that no pictures can be used that show student faces or student names on it. 

Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 8th grade science core.

Updated October 24, 2008 by: Glen Westbroek

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