Optical illusions & more
Optical illusions, brain teasers...
An optical illusion, according to the dictionary, can be defined as a visually perceived image that is deceptive or misleading. Some of the below images are printable ('Printable' meaning here that the optical illusion would work on paper as well) while others aren't.
(Please click on the thumbnails to see the proper versions of the illusions.) (NOTE: In order for most of the illusions to work correctly, you'll have to see them in their proper size.)
Optical illusion 1
Concentrate at the centre and slowly move your head back and forth.
(Printable)
Brain Teaser 1
Which side is this window facing?
(Printable)
Brain Teaser 3
A cube in a room or a cube with a bit missing?
(Printable)
Optical illusion 3
There aren't two triangles in the image; there is only one. The gaps in the red triangle outline and the circles make it seem as if there is another white one.
(Non-printable)
Optical illusion 5
AB or BC, which is longer?
(Printable)
ANS: Both AB and BC are of equal length.
Optical illusion 7
Arrow tip to arrow tip, which length is longer?
(Printable)
ANS: What do you think?
Optical illusion 2
You must have seen this spiral rotating while you were viewing the rest of the page. Now you see it's just an ordinary image. Strange, right? (To make it rotate, you have to look elsewhere on the page, without gazing at it directly)
(Non-printable)
Brain Teaser 2
(Printable)
Brain Teaser 4
Is this the book cover or the inside of the book?
(Printable)
Optical illusion 4
Concentrate on the 3rd or 4th dot (in the centre) for about 40 seconds. Then blink a few times on a white wall. What do you see?
(Non-printable)
Optical illusion 6
Can you see the diagonal grey lines?
(Non-printable)
Optical illusion 8
Are the two centre circles the same size?
(Printable)
ANS: Surprisingly yes
Optical illusion 9
Look at the above image. Doesn't it look ... weird? 
(Non-printable)