Crepuscular rays are also called as “Sun
rays” in atmospheric optics, are actually rays of sunlight that appear to
radiate from the point in the sky where the sun is located. These rays, which
stream through gaps in clouds mainly stratocumulus or between other objects,
are columns of sunlit air separated by darker cloud-shadowed regions. In spite
of seeming to converge at a point, the rays are actually fact near-parallel
shafts of sunlight, and their apparent convergence is a perspective effect
alike, i.e., to the way that parallel railway lines seem to converge at a point
in the distance.
The name comes from their frequent
occurrences during twilight hours those around dawn and dusk, when the
contrasts in the middle of light and dark are the most obvious. The name
“Crepuscular” comes from the Latin word "Crepusculum", which means
twilight. The rays in some cases may spread across the sky and appear to
converge at the antisolar point, the point on the sky sphere directly opposite
the sun. In this case they’re called anticrepuscular rays. These are not as
easily spotted as crepuscular rays. This apparent dual convergence to both the
solar and antisolar points is a perspective effect analogous to railway tracks
appearing to converge to opposite points in opposite directions.
Color
Crepuscular rays are frequently red or
yellow in appearance since the path through the atmosphere at sunrise and
sunset passes through up to 40 times as much air as rays from a high midday
sun. However; particles in the air scatter short wavelength light blue and
green through Rayleigh scattering much more strongly than longer wavelength
yellow and red light.
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