I Can See A Rainbow!

Lorraine I. Crump              Lawndale Community Academy
                               3500 W. Douglas
                               Chicago IL 60623
                               312-534-1635

Objective: 

As a result of this lesson, students will be able to identify the colors of a 
rainbow using the mnemonic ROY G BIV. They will also recognize primary colors of 
light.  The student will have an understanding of light blending to form new 
colors.  Finally they will answer the question; Why is the sky blue? 

Vocabulary:

Retina    Indigo    Magenta    Violet    Primary  Cyan

Materials: 

     1. Three slide projectors or overheads, one of these should be a overhead.

     2. Three color filters blue, red, yellow.

     3. Various objects of bright colors.

     4. Scissors, crayons, pencils each student will need these.

     5. White cardboard.

     6. Diffraction paper.
     
     7. Construction paper, one sheet each of red, orange, yellow, green, blue 
        indigo, and violet.

     8. One glass of water, 1/2 teaspoon of coffee creamer.

     9. A flashlight

    10. A diagram of the human eye.

Strategy:

The teacher will need to have a cardboard circle measuring 31/2" diameter for each 
student.  Divide the circle into eight.  The construction paper should be cut 
into arches to form a rainbow.  Place the beginning letter of the color at the 
top of the arch i.e., R on the red, O on orange, etc.  The three projectors 
should be set up in such a way that all three light beams will meet on a white 
screen.  One color filter is placed near each projector.  The diffraction paper 
should be cut into a small enough square to be tape over the light of the 
overhead.  Spoon coffee creamer into water, do not stir let powder sink to 
bottom.  Set aside for latter demonstration.  Using the diagram of an eye 
explain the following:  Light entering your eye hits the retina stimulating 
cones, then a message is sent to the brain telling you this is the color. 

Activity 1:

The teacher will begin this activity by showing the students a rainbow.  This is 
done with the previously describe overhead-diffration paper set up.  Cut on 
projector, ask students to describe what colors they see.  Next have students 
take the corresponding color and tape it to the board forming a rainbow.  When 
this is complete ROY G BIV is viewed, the teacher should tell students this is 
the way to remember the colors of the rainbow. 

Activity 2:

Place a red filter over one projector showing a red beam of light on a screen. 
Then do the same with the green filter.  This should result in the two colors of 
light forming yellow on the screen.  This should be done with red and blue to 
make magenta and blue plus green to make cyan.  Explain that these colors are 
called primary colors of light because when combined they make up all the colors 
of the rainbow.  The mnemonic for this is RGB.  Finally combine all three to 
form white light.  Next have students step in the path of white light, look at 
their shadow.  What colors do you see? 

Activity 3:

Place two filters on the overhead not over lapping.  Then have students place an 
object in front of the light. Look at the color the object takes on.  Discuss. 

Activity 4:

Project a red light on the screen.  Have students stare at it for 30 seconds. 
Turn off light.  Do you still see a red screen?  No the red cones in your retina 
are tired.  The color you see is from the cones that are not tired. 

Activity 5:

Why is the sky blue?  The teacher will shine the flashlight onto a glass from 
above and move slowly down the back.  Note the water color.  Explain to the 
class that the particles of powder cream scatter the light from the flashlight.  
Putting the flashlight behind the glass causes the blue light to scatter aside 
allowing only orange-red light to be seen.  Placing the light above the glass 
causes less light to scatter and more blue light is seen.  Thus the water looks 
blue.  When applied to the atmosphere, the flashlight is the sun, the water, the 
sky and the creamer are air particles. 

Activity 6:

Give each student a wheel (circle), a red, blue, green crayon, pencil.  Have the 
students color the wheel using two colors on each.  Next push the pencil through 
the center.  Spin the wheel to see a new colors. 

Performance Assessment:

Give the students the following story.  Their reply should use a rainbow 
diagram, name each color on it, tell why the sky is blue also give an 
explanation of primary colors used to form all colors. 
   Once upon a time it was a rainy day.  Karlene and her friend April waited for 
the showers to end before going out to play.  Once outside April said "WOW look 
in the sky, a rainbow!"  Describe what the third graders had seen and why? 

Rubric:

5 points  Answers correctly with clear sound multi-faceted logical arguments
          (diagrams, examples, sketches, etc.)

4 points  Answers correctly with clear explanation and a diagram.

3 points  Answers correctly but reason is unclear.

2 points  Partially correct with effort toward explanations.

1 points  Answers with no supporting evidence.

0 points  Answers of "I don't know."

Multi-cultural Project:

The classroom bulletin board can be set up with a rainbow.  Highlighting the 
mnemonic ROY G BIV.  Children of multi-cultures can be looking up at it.  The 
caption reads LOVE COMES IN ALL COLORS.