Zollner's Illusion

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In this Illusion, the Vertical lines in the above figure are Parallel, but appear to be tilted at an angle.

See also Illusion

References

Jablan, S. ``Some Visual Illusions Occurring in Interrupted Systems.'' http://members.tripod.com/~modularity/interr.htm.

Pappas, T. The Joy of Mathematics. San Carlos, CA: Wide World Publ./Tetra, p. 172, 1989.