 Crepuscular rays, dawn, Santa Barbara, California Crepuscular rays is a term used in atmospheric optics for when light beams which appear to radiate from a single point in the sky. The name comes from their frequent occurrences during twilight, where the contrasts between light and dark are the most obvious.
Crepuscular rays are parallel, but appear to diverge because of parallax. They are often seen through sunlight shining through holes or breaks in cloud cover. Three main forms of crepuscular rays are:
- Rays of light penetrating holes in low clouds (Jacob's ladder)
- Beams of light diverging from behind a cloud
- Pale, pinkish or reddish rays that radiate from below the horizon
The rays of the second and third types, in some cases, may extend across the sky and appear to converge at the antisolar point on the opposite horizon, and they are called anticrepuscular rays.
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