Bending White Light

L'Ouverture Perkins            William W.Carter
                               5740 S. Michigan Ave.
                               Chicago IL 60637
                               (312) 535-0860

Objectives:

The objective of my mini-teach is to demonstrate that white light is made up of 
many colors.  The process objective is to observe examples of the spectrum 
produced by white light. 

Materials Needed:

    Per Group Of 4

1 large container
1 mirror
1 flashlight
1 pitcher of water
1 roll of tape
50 cm of cord, twine or string for each student
1 set of tempera or brightly colored markers
4 sheets of cardboard (8 1/2 x 11) or construction paper
  (or you could use color wheels that have the colors of the spectrum
   on one side and a blank circle on the back.  These can be purchased
   at the American Science and Surplus store on Northwest Highway).
1 cup of dishwashing liquid with a little bit of glycerine added

Strategy:

1.  Set the mirror in the large container.  Lean the mirror against one end of 
      the container at about a 45 degree angle.  Tape the mirror to the edge of
      of the container to keep it from sliding.  Then fill the large container
      about 3/4 full of water.  The mirror should be half-in and half-out of the
      water.
2.  Shine the flashlight against the wall.  Ask students to identify what they
      see.  Explain that the light from the flashlight is called white light.
3.  Shine the flashlight onto the half of the mirror that is out of the
      water.  The reflection of the light from the flashlight may be focused on
      the wall, the ceiling, a screen, or a large piece of white paper.  Ask
      the students to observe the light and describe it.      
4.  Shine the flashlight onto the submerged part of the mirror and focus the
      reflection so that it may be seen by the class.  Ask students to observe
      and describe the reflected light.  List the colors students observe and 
      in the order in which they appear.
5.  Ask students for their hypothesis as to why the light reflected from under
      the water produced different colors.  Students may think that the colors 
      come from the water and not from the light itself.  You may want to 
      explain that white light contains all the colors of the rainbow. when
      the white light goes through the water, the colors in the light are bent.
      Some of the colors are bent more than others.  When the colors of light
      leave the water, they go in slightly different directions, thereby 
      separating the colors.

Performance Assessment:

       In this activity, students will create a "color mixer" with paper and
       crayons.  Students are to follow the directions and record their 
       observations.
1.   Use brightly colored paint or markers to color the 6 sections of your
       color wheel.  Color each section one of the following colors: red, yellow
       orange, green, blue and violet (indigo).
2.   Make two small holes near the center of the circle, about two centimeters
       apart.  Pass a 50 centimeter piece of cord through the two holes.  Tie
       the two ends of the cord together.
3.   Hold the cord by the loops in each end and ask a friend to slide the circle
       along until it is midway between your hands.
4.   Twirl the circle until the cord is tightly twisted.  Then gently pull on 
       the loops.  The circle should spin at a high speed.
5.   Watch the circle as it spins.  What do the colors appear to do?
6.   Slow down the speed of the spinning circle.  How well can you see the six
       colors?
7.   As the circle spins faster and faster, what happens to the six colors?
8.   As you watch a rapidly spinning object, such as a top or a carnival ride, 
       are you able to see the true colors of the object?  Why or why not?

References:

       Harcourt Brace Jovanovich  Teachers Guide and Resource Manual 1987