Optical Illusions

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Optical Illusions
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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.
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Creating Simple Illusions
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1. Cut out both circles for Set 1 or Set 2.

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1. 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.

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1. 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.

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1. Hold the straw in both hands at arms 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!
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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.
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Investigating Other Illusions
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What do you see?

Two faces or a vase?Did you see one an then the
other?
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.
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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.
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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.
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Which center dot is larger?
They are the same size. The surrounding dots
cause distraction.
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Are the horizontal line segments straight?
Yes, Measure the distance between both ends of
the lines to check .
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Are these horizontal line segments straight?
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A few more illusions
How many shelves do you see?
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(No Transcript)
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What do you see?
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What animal is this?
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Time to see if you can create your own illusions.
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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.