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White Light and Colored Shadows

  • Introduction
  • Video& Results
  • Materials
  • Procedure
  • Preparation & Notes
  • Download Files

White Light and Colored Shadowscolor_spheres

Not all shadows are black! In this activity, students will see that the sum of red, green and blue (RGB) light is white light. When one color of light is blocked with an object, the color of its shadow is the sum of the two remaining colors. 

Colored light are added to produce a  new light as follows:rgb hand shadow

red + blue = purple
red + green = yellow
blue + green = aqua

 

 

None for this activity.

 

 

Materials – Projecting White Light

  • 1 power strip with at least 7 plugsrgb materials
    (check to make sure the chord is long enough)
  • place to plug into the wall
  • white surface to shine the light in a darkened space
  • 1 green, 1 red and 1 blue light bulb
    (50 watt bulbs we used get hot)

    In San Diego, Light Bulbs Unlimited & Lighting Solutions is helpful.
    1017 Morena Blvd.
    San Diego, CA 92110
    Phone: 619-296-2454
    Fax: 619-295-4922
    Email: lightbulbsu@aol.com


Activity – Creating colored shadows

  1. Screw light bulbs into socket adapters.
  2. Plug light bulbs into the powerstrip with switch off.
  3. Flip switch on and project onto a white wall in a darkened space.
    project_rgb_explore		
    (Image adapted from http://www.exploratorium.edu/snacks/colored_shadows/index.html)
  4. Allow children to create shadows with their hands and objects.
    rgb_setuphand shadow
  5. Cover one bulb at a time and have the students identify the color of the light on the wall and the color of their shadows.
  6. Have the students formulate methods for creating red, green, yellow and blue shadows

Preparation Ahead of Time & Information
No advanced preparation really necessary. The bulbs get hot, so it will be useful to create a stable base and to have some extra bulbs in case one breaks.

References and other sources

http://www.exploratorium.edu/snacks/colored_shadows/index.html