Optical Illusions

What is an Illusion? Something that seems to be different from what it really is. What is an Optical Illusion? A picture of an image that tricks your eyes and makes you see something that is not actually there.

Creating Simple Illusions

1.Cut out both circles for Set 1 or Set 2.

2.Place the circles back-to-back, lining up the arrows at A and B. Staple the circles together at the left and right, near the edge.

3.Slip a drinking straws between the circles so it lines up with the arrows at A and B. The arrows should be centered on the straw. Staple through the straw and circles near the arrows at A and B to make a lollipop shape.

4.Hold the straw in both hands at arm’s length. Twirl the straw rapidly by moving your hands back and forth against each other. Watch the design as you spin the circles. Describe what you see!

This phenomenon, called persistence of vision, happens because the brain remembers an image of what is seen for a short time after it was viewed. If a second image comes rapidly into view, the brain interprets the second image as part of the original image, and the viewer sees one combined image.

Investigating Other Illusions

What do you see? This is a figure-and-ground illusion, in which the viewer sees one part as the figure and the other part as the ground. The figure and ground tend to reverse, often without conscious effort. Seeing one aspect excludes seeing the other. Two faces or a vase? Did you see one an then the other?

This figure is a different kind of illusion in which the figure seems to reverse. Describe any changes you see. The diagram of the cube, seen as a 3-dimensional object, seems to change its orientation. It flip-flops.

Are the horizontal line segments the same length? Yes, some figures are illusions in which lines or the arrangement of objects creates a false impression of length or distance.

Which center dot is larger? They are the same size. The surrounding dots cause distraction.

Are the horizontal line segments straight? Yes, Measure the distance between both ends of the lines to check.

Are these horizontal line segments straight?

A few more illusions How many shelves do you see?

What do you see?

What animal is this?

Time to see if you can create your own illusions.

Homework Options Homework Options Investigate more optical illusions on the Internet and write a brief paragraph describing one of the illusions you enjoyed. Write a brief paragraph describing one of the illusions you enjoyed in class today. Draw your own version of the optical illusions involving line segments.