Colors

Schaumburg, Carl                     Von Stueben MSC
                                     1-312-509-5000
                           
Objective

1. Students will understand what colors are in white and other colors of light. 
2. Students will understand complementary colors and that colors we see are the 
   result of some colors being removed from white light. 

Apparatus Needed

An overhead projector
Various colored pieces of plastic (the whole spectrum if possible) 
Various pieces of colored paper

Recommended Strategy

    Starting with a clear piece of plastic on the overhead screen, ask, "Has anyone 
heard that white light contains other colors.  How can white be separated into its 
colors?"  Answers of prism, etc. may be suggested.  None of these should be present.  
Place a piece of red plastic accidentally over the clear piece.  "Is there red light 
in white?"  Yes, because you can see the red light coming through.  "What about other 
colors in white?  Are there other colors in yellow and other colors?"  Have class 
find out by overlapping colored pieces of plastic and holding them up to the light.  
Data table can be developed and discussed. 
    Ask, "Why is the asphalt street so much warmer than the sidewalk if you are 
walking in bare feet?  What colors come through black?"  None, the colors are changed 
to heat.  "What happens to the colors that don't come through various colors?"  
Changed to heat too.  "How could we check this out?"  Thermometer. 
    We can get our eyes to automatically show what colors are removed from light when 
we look at any color.  Place a white piece of paper on the desk with a small x in the 
center.  Place a colored piece of paper next to the white page and stare at the 
center of the colored piece, counting to 30.  Quickly shift your gaze and 
concentration to the x on the white sheet.  The color removed from white light (the 
complementary color) when you looked at the first color should now appear.  Make a 
table of the complementary colors.  To test your results, select a color and place a 
small piece of its complement in the center.  Count and shift your vision.  If your 
colors are complementary, they will switch places.  Discuss how this is useful; 
looking at objects under mercury or sodium vapor lights at first appear the wrong 
color, but eventually the colors seem more normal. The concept that colors are 
removed from white light could be discussed by asking what colors are removed 
(complementary colors) by looking at colors of clothing around you and what colors 
are removed from light by leaves. 
    Finish up by projecting on the overhead a flag with green stripes in place of red 
with opaque stripes of masking tape for the white, yellow field in place of blue, and 
paste-on opaque stars.  Play the Star Spangled Banner.  About half-way through the 
song remove the overhead slide, but have everyone continue to stare at a spot on the 
screen.  The normal colors will appear for the rest of the song.