Optical Illusions Lesson Plan

Goal of Lesson

The purpose of this lesson is to introduce students to basic principles of visual processing. Perception and sensation are not necessarily the same; optical illusions are a way for us to study the way that our visual system works.

What is the theme for this quarter?

Optics (Which is the study of light)

Recap from last week

-  What was last week lesson about? (Dissecting Cows eyes)

-  What did you learn/ what was pretty cool about this lesson? (Students will throw out a bunch of thoughts and we can re-enforce the concepts that were learnt like the different parts of the eye and functions)

-  So we collect light in/through the eye, but how do we process that information? (In our brain)

Today’s Lesson; what is an optical illusion?

Today we are going to explore and make different types of optical illusions. Some illusions show us one thing in a picture, while someone else sees something entirely different in the same picture (the old lady or the young woman). Other illusions can be designed to over-stimulate our visual system and trick us into perceiving something differently than from what actually exists. In other words, what we see does not correspond to physical reality. Because there are limited cells in the visual system that specifically responds to particular aspects of visual stimuli, these cells can become fatigued.

What do you see?

Awareness Test

http://www.youtube.com/watch?v=Ahg6qcgoay4

http://www.youtube.com/watch?v=z9aUseqgCiY

How were these optical illusions; did we perceive a different physical reality?

-  No, same lighting when you watch the clip

-  Brain has limited capacity to process information (that’s okay)

How weren’t these optical illusions? These weren’t optical illusions as much as they were distractions; we didn’t see movement or color different from reality – our sensation was the same, but our perception was different.

Here are some example optical illusions.

1) Rotating Snake

http://www.ritsumei.ac.jp/~akitaoka/rotsnake.gif

2) Hermann Grid

Dark patches appear in the street crossings, except the ones which you are directly looking at.

http://www.michaelbach.de/ot/lum_herGrid/index.html

3) Spiral After Effect

Stare at the center of the rotating spiral for about 20 seconds, then look elsewhere. You will notice that whatever you look at now appears swirling. The effect goes away after a few seconds.

http://www.michaelbach.de/ot/mot_adaptSpiral/index.html

4) Stepping Feet

Observe the movement of blue and yellow “feet”. The feet seem to step alternately, like tiny feet going tip-tap-tip-tap… This is more pronounced if you do not look directly on the feet, but between them. In reality their movement is always parallel.

http://michaelbach.de/ot/mot-feetLin/index.html

5) Breathing Square

Track the blue shape hidden by the orange squares. After one cycle you know that there is a blue square of constant size, which slowly rotates. But to nearly every observer it looks like the square is changing its size, “breathing” so to speak.

http://michaelbach.de/ot/mot_breathingSquare/index.html

Make your own optical illusions.

Break students out in groups and try a few experiments

Experiment 1 – Fast Money

Supplies:

2 pennies

Procedure:

Step 1- Get two identical coins.

Step 2- Hold them together between your two index fingers by pressing your fingers together.

Step 3-Rub the coins against each other rapidly up and down.

Step 4-Did an image of a third coin appear?

Experiment 2 – A Hole in the Hand

Supplies:

A-4 paper or construction paper

Procedure:

Step 1- Take a piece of printer (or construction) paper and roll it into a tube.

Step 2- Put one end against your eye and close the other one.

Look at something 15 feet away for about 10 seconds.

Step 3- Put the opposite hand next to the tube. For a real treat put you hand about 5 inches away from the end of the tube.

Step 4- Open the other eye. What do you see?

Step 5- Do you see a bloodless hole in your hand? Your hand in your own hand!

Experiment 3 – 2D to 3D Hand

Supplies:

White paper (make it just larger than the hand being drawn, this is a 8.5x11 inch piece of paper cut in half)

Pencil

Colored markers (use at least 3 different colors/shades)

Procedure:

Step 1- Place the hand to be drawn on a piece of paper

Step 2 – Use the pencil to trace the hand and a section of the wrist

Step 3 – Choose 3 different colored markers

Step 4 - Start drawing across the width of the paper. When you finally reach the pencil line of the drawing of the hand, curve the line a little upward in a gentle arc, ending on the other side of the hand line at the same level as you started. Keep adding the curve each time you come to a hand print line.

Step 5 – Repeat this process but using a different color each time and make sure to maintain the color order.

End Product should look like this

Experiment 4 – Making an Arrow Illusion

Supplies:

4 pipe cleaners (2 same color, 2 different color)

Ruler

Procedure:

Step 1 - Take two pipe cleaners that are the same length and the same color. (If they aren't the same length and color, the optical illusion will not work)

Step 2 - Now, cut in half two other pipe cleaners that are a different color. You will use these different colored pipe cleaners to make the ends of your arrows

Step 3 - Wrap the middle of one short pipe cleaner around the end of one long pipe cleaner. Then bend the short one in half so it looks like an arrow. Repeat this process on the other side.

Step 4 - Then, repeat with the other pipe cleaner, but this time, your arrows on the ends will be turned in the opposite direction (an inverted arrow).

Step 5 - Now, take your completed pipe cleaners and hold them up side by side. Then, slowly move your pipe cleaners apart. You have created an optical illusion!

Explain what you noticed as you moved them apart below. Also, which pipe cleaner looks longer (not including the arrows)? (Have a ruler handy to show them they are of equal length)