MIRROR ILLUSION

A mirror creates an “illusion” of another object or person being present.

Mirror Ball by M.C. Escher

Refraction

A light ray bends when it enters a different density medium at an oblique angle.
The density of a material affects the speed of light ray traveling through it.

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A straw in a glass of water appears broken at the surface
of the water and its size and angle different under the water.

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An underwater object appears under different
angle when viewed at the edge of an fish tank.
Both A1 and A2 are apparent positions of the object A.

When light passes from one substance to another, it changes direction. This effect is familiar to all of us from observations in bath tubs and swimming pools, and it is called refraction. The effect is usually dealt with as if light were rays that literally bend in direction as they pass through the boundary, but in fact the elegant explanation of what happens relies on the wave theory of light.

More information: www.math.ubc.ca/.../ refraction/refraction.html

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