the bending of light

Refracted light is light that bends as it travels from one substance to another.

The amount of refraction that occurs depends upon the density of the substance and the angle at which the light is entering the substance.

Photograph by Bob Rauber
The refraction of sunlight (or moonlight) by ice crystals can result in a number of beautiful optical effects like halos which are produced when sunlight or moonlight is refracted by the pencil-shaped ice crystals of cirroform clouds.

Photograph by Bob Rauber
Sundogs are the result of sunlight refracted by slowly falling, hexagonal-shaped ice crystals.

Light refraction is also responsible for other unique effects, like bending the rays of a setting sun to give it an elliptical, "flattened-out" appearance.

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Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.