Optical Illusion Sequence

by Codi Anderson and Jason Pieratt

Concept:  Optical illusions are the misperceptions of stimuli received by the eye and interpreted by the brain.

Background Information: The illusion of motion results from the brain’s inability to separate a series of rapidly changing images.  Afterimage is a type of illusion that results when we over-stimulate our vision.  Afterimages are a result of a temporary depletion of a substance called visual purple.  Visual purple is a photosensitive pigment within the light-sensitive portion of the eye.  When our eyes become over-stimulated by visual stimuli, visual purple becomes depleted.  Perspective is a way of seeing things so that they appear to have depth.

Activity Sequence:

  1. Saturate and Surround Color
  2. Hello Red Fox
  3. Optical Illusion Poster
  4. Spinning Wheels
  5. Where did it go?
  6. Persistence of Vision
  7. Pencil Flipper
  8. Rotoscope
  9. False Perspective Window

Activity

Saturate and Surround Color

Materials: markers, drawing paper

Procedure

Take a red or green marker and completely color a square or triangle on white paper.

Stare at that colored shape for one minute.

Now look at a plain piece of white paper. “What do you see?”

Your eyes are saturated with red and see the complementary color green.  The cones, photoreceptors in the eye that are responsible for color vision, become tired, resulting in your eye seeing the complementary color.

Activity

Hello Red Fox

Materials: the book Hello Red Fox by Eric Carle

Procedure

Begin by reading the story Hello Red Fox by Eric Carle.

As you read the story, stop and allow the students to follow along with the directions given at the front of the book.

Students will see that after staring at the object and looking at a blank white page, they will see that complementary color of the color of the object they were staring at.

Have students list a color found in the book and then write what color they see after looking at white page.

Activity

Optical Illusions Poster

Materials:  “Go or Stop” poster, time-watch or clock with second hand

Procedure

Divide your students into pairs.

Have one student be the observer and one student be the timekeeper.

Instruct the observer to stare at the “Go or Stop” poster (Science Video Adventures, Optical Illusions; Michael DiSpezio; Addison-Wesley Publishing Company) for 15-20 seconds, concentrating on a spot within the white G.  Then have them shut their eyes or look at a white wall and describe what they see.

Instruct the timekeeper to allow the observer 15-20 seconds to stare at the poster.  Then have them write down what after images the observer sees.

Have them trade roles when completed.

Have the students write or draw their explanations for what happened.

Activity

Spinning Wheels

Materials:  crayons, scissors, poster board, compass, yarn or string (1/2 yard per student)

Procedure

Have each student cut out a card board circle (approximately 5” in diameter) by using a compass.

The front and back of each circle should be divided into pie-like sections of equal size, by drawing lines to show those sections.  Students should select the colors and completely fill each with one color.

Poke a small hole at the circle’s center.

Pull yarn or string through the hole.  Swing the string and circle until the entire length of the string is twisted.  Then briskly stretch the string with a firm pull.  Watch the wheel spin and the colors merge.

Ask the students why they think this illusion occurs.

Explain that the wheel is spinning so fast that instead of seeing each color separately, our eyes see a mixture.

Activity

Where Did It Go?

Materials:  crayons, construction paper, markers, scissors, white paper, poster board, colored plastic food wrap, clear adhesive tape.

Procedure

Students should draw patterns of lines and shapes using crayons or markers on paper and construction paper crayons on colored paper.  Use them to experiment with both dark and light papers and with various color patterns.

To create “color filtered glasses” have students cut out eyeglass frames from cardboard.  Create colored filters using colored food wrap and tape these into the lens area.  Create some glasses with red, green, and blue “lenses”.

Ask the students do the patterns drawn on the paper seem to change depending on which glasses are worn.

Activity

Persistence of Vision

Materials: crayons, 3”x 5” index cards, straw or pencil, clear tape

Procedure

Give each student two index cards, and ask them to draw a bird on the center of the plain side of one card and an empty bird cage on the plain side of the other card.

Tape a straw or pencil on the back of the card.  Then tape the sides and top of the two cards together.

Have the students roll the pencil between their hands very quickly while observing the two drawings.  “What happens?”

Explain that the images are moving faster than the eye and brain can receive them.

Activity

Pencil Flipper

Materials: pencil, scissors, stapler, sheet of bird and cage image

Procedure

Cut out the pattern of the bird and cage (see attachment A).

Fold the paper in half along the dotted line, and place the set of images over the top of the pencil.  Staple the paper on either side of the pencil.

Rapidly move the pencil in the palms of your hands and observe the illusion.

Have the students write down what they see.

Create other pairs of images for your pencil flipper.

Activity

Rotoscope

Materials:  rotoscope pattern (see attachment B), sheet of images sheets, construction paper, ruler, pencil, scissors, paste, tape, turntable.

Procedure

Trace the rotoscope pattern twice on the construction paper.

Cut out the rotoscope patterns and two strips of bird images.

Paste the two rotoscope patterns together.  Paste the two strips of bird images onto the inside bottom of the rotoscope.  Tape the ends of the rotoscope together to form a circular shape.

Spin the rotoscope on the turntable while looking through the slots at the bird images.

Record the observations.

Activity

False Perspective Window

Materials: false-perspective window (see attachment C), 2-4 ft. of string, tape, straws, and scissors.

Procedure

Have the students tape the end of the string which is attached to the perspective window to the edge of the desk, making sure the perspective window is at eye level when sitting on the floor by their desks.

Twist the string 30-50 times in order to get the proper rotation speed

Have the students stand 2 ft. away from their false-perspective windows hanging in the doorway or hanging from their desks and cover one eye.

Have them watch the rotating window, focusing on the narrow end of the window.

Have students write down their observations.

Ask the students why the straw seems to be passing through the perspective window.

Have the students write or draw their explanations for what happened.