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Optical Illusions

Optical Illusions         After Images         Stereo Images        M.C. Escher         Links 

 The following optical illusions were taken from EncycloZinehttp://EncycloZine.com/Illusions/

Optical Illusions
       The brain takes cues from images received from the eyes to help it interpret what is being seen. Usually this is important for things like depth perception, but occasionally it leads us astray. The cues deceive us into thinking we see something that isn't true, or isn't even there. In the pages that follow, you will see that we can arrange marks on the paper or on the screen, that will fool your mind into seeing a false reality. Identical lines will appear to be different lengths, ghostly dark blobs appear where the screen or paper is white, black and white patterns appear to move when they can't, etc. They can be so convincing that you may have to check for your self that there's no trickery involved.



Some of the most powerful and well-known illusions involve the distortion of reality, such that distances appear longer or shorter than they really are, straight lines appear to bend, and parallel lines seem to converge.


Some two-dimensional figures can be interpreted as solid objects in more than one way. A well-known example of this is the flat representation of a wire-frame cube, which can be seen as if from above, or below.


These tiles create surprising optical illusions when repeatedly copied to fill the screen. See if you can predict the effect of each...

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Is the blue face in front or behind?

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Ghostly dots appear between the squares

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The word 'Liar' makes a face

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Necker cube- how is it oriented?  Are you seeing it as if from above, or below?

Click here for animated Necker Cube

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Which of the two inner circles is larger?  They are both the same size

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The purple lines are parallel but appear bent

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The diagonal lines are in fact, parallel.


The lines of the "V" are the same length


The top lines of the two quadrilaterals are the same length.


The two inner circles are the same size.


The single line if continued joins with the lower of the pair, not the top.


You can see the staircase as if looking from above - or from below.


The lines appear to bend inwards but are actually straight.


The lines appear to bend outwards but are actually straight.


The lines appear to bend inwards but are actually straight.


The farthest block appears larger than the nearer ones but is the same height.


You may see the slabs as if from above or from below


The shape is in fact a circle.

Cube in a Corner

This picture is ambiguous in three ways:

  • As a small cube in front of a larger cube;
  • As a large cube with a corner cubelet cut out;
  • As a small cube inside three perpendicular adjoining planes.
A wine goblet - or two faces in profile?
The white triangle looks very real, although there's no triangle, per se.
Is it a man playing a saxophone, or a girl's face?
Do you only see black shapes on white - or a word?
A very famous illusion - young lady or old hag? In 1915, a cartoonist named W.E. Hill first published this drawing. It's hard to see what it's supposed to be. Is it a drawing of a pretty young girl looking away from us? Or is it an older woman looking down at the floor? Well, it's both. The key is perception and what you expect to see. Here's a hint: The young girl's necklace is the older woman's mouth. The young girl's chin and jaw are the older woman's nose.


In 1860, J. C. Poggendorf, the editor of a journal of physics and chemistry, received a monograph from Zöllner describing his illusion. Poggendorff noticed and described another effect of the apparent misalignment of the diagonal lines in Zöllner's figure. Thus the Poggendorff illusion was discovered.

It is possible to build this - to be viewed from one special position. However, the general object is impossible.
An elephantine variant of the impossible trident.
Image: Old Girl - Courtesy Sharon Silvia

Swedish artist Oscar Reutersvard is the "father of impossible figures." He was the first to deliberately make impossible figures


Look at the image above. Move your eyes around it. Do the dots at the intersection appear to scintillate?





After Images


     Steadily fixate on the black light bulb for thirty seconds or more. Try not to avert your gaze. Immediately turn your gaze to the white region on the right adjoining the bulb (or a blank white sheet of paper). You should see a glowing light bulb!


Stereo Pictures

To see the stereo view, fuse the image. If you cross-fuse, use the right most two images, and if you diverge-fuse, use the left-most two images.


To see the stereo view, fuse the image. If you cross-fuse, use the right most two images, and if you diverge-fuse, use the left-most two images.

M.C. Escher
Ascending and Descending
Day And Night

Mobius Strip II            Relativity

Fish and Boats; Symmetry 72

Optical Illusion Links

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Website by Duncan Wilson

Page last updated January 07, 2012

The links on this page connect students to resources, which are recommended because of their educational content and value. I do not intend your child to visit any pages beyond those to which I have provided specific links. We recommend that you supervise/monitor your child's Internet activity at all times.