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Thursday, February 11, 2010

Optical illusions

Posted by abhishek parikshya



1. Blivet
It appears to have three cylindrical prongs at one end which then mysteriously transform into two rectangular prongs at the other end.

2.Café Wall Illusion
The café wall illusion is an optical illusion, first described by Doctor Richard Gregory. He observed this curious effect in the tiles of the wall of a café at the bottom of St Michael’s Hill, Bristol. This optical illusion makes the parallel straight horizontal lines appear to be bent. To construct the illusion, alternating light and dark “bricks” are laid in staggered rows. It is essential for the illusion that each “brick” is surrounded by a layer of “mortar” (the grey in the image). This should ideally be of a color in between the dark and light color of the “bricks”.


3.Fraser Spiral Illusion
 The illusion is also known as the false spiral, or by its original name, the twisted cord illusion. The overlapping black arc segments appear to form a spiral; however, the arcs are a series of concentric circles.
  4.Hermann Grid Illusion
The Hermann grid illusion is an optical illusion reported by Ludimar Hermann in 1870 while, incidentally, reading John Tyndall’s Sound. The illusion is characterised by “ghostlike” grey blobs perceived at the intersections of a white (or light-colored) grid on a black background. The grey blobs disappear when looking directly at an intersection.
 5.Impossible Cube Illusion
The impossible cube or irrational cube is an impossible object that draws upon the ambiguity present in a Necker cube illustration. An impossible cube is usually rendered as a Necker cube in which the edges are apparently solid beams. This apparent solidity gives the impossible cube greater visual ambiguity than the Necker cube, which is less likely to be perceived as an impossible object. The illusion plays on the human eye’s interpretation of two-dimensional pictures as three-dimensional objects.

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