THE EYE AND COLOR IMAGES
LACY GRIGSBY Paul Robeson High School
6835 S. Normal Avenue
Chicago, IL 60621
Objectives: 1) To have the student to observe and experiment with
visual after images.
2) To have the student observe white light and its
component color spectrum.
3) Introduce the student to the basic colors and their
complements within the visual system by demonstration.
4) Introduce the basic parts of the eye.
5) To demonstrate how the optical path and focal system
6) To demonstrate how an image is projected upon the
7) Show feature analysis of illusions produced by after
8) To show the student how to derive any given color.
Materials: Candle, convex lens, overhead projector, color light box,
3 by 5 index cards, envelopes, small triangles (red, blue,
green, and yellow), drawings or pictures, matches, and model
of the human eye.
Strategies: Pass out envelopes containing four different colored triangles
and an index card. see below
_______________________________________ .. . .
= __ = . . . .
PA = = = = . . . .
= = = = . .......
= = = = = = ...... .
= = = = . ..
= = = = .. . .
= = __ = = . . . .
= = . . . .
_______________________________________ . .......
Have the students in the class place a red triangle in the
center of the circle. (Make sure that the student
concentrates on looking at the triangle for at least
45 seconds). When the time is up have them stare at the dot
on the other end of the card.
You should ask them if they see anything unusual as they are
staring at the dot. ans. (A blue after image). Wait six
minutes then have them try another color on the card.
Each time they should see an after image of the
complementary color(s). If you have students that don't
seem to see the after image, show them the handouts I
gave you or pictures from Human Information Processing
page 216a thru 216d. This may them to see the phenomena
and identify the colors.
Light box=PA The color light box should be used at this point. Show
the complementary colors, and the white color produced
& when the three basic colors of light are added together.
The triangle of colors should be put on the overhead
Triangle= also, to show the student to derive the other colors
chalkboard and their complements. NOTE The room should be dark.
Take the candle and put it about two feet in front of
Image=PA the object you would like to project your image upon.
Light the candle. Take the convex lens and move it back
and forth between the candle and the screen until you
find the focal point. (The candle image should now be
projected on the screen in full living color, upside
down). This is the time to pull out the model of the
eye and show them how the eye works.
These PA's should lead to all sorts of wonderful
discussions about photochemicals and proteins, eye
structure and function, images and after images,
component colors of white light, and colors and their
References Lindsey, Peter, and Norman, Donald. Human Information
Processing. New York: Academic Press, 1973.
Otto, James, and Towle, Albert. Modern Biology New
York: Holt, Rinehart and Winston, 1977.
Return to Biology Index