Natural Phenomenon : Crepuscular rays

Crepuscular rays, more commonly known as sunbeams, sun rays, splintered light, or god rays, in meteorological optics, are rays of sunlight that appear to radiate from the point in the sky where the Sun is located. Shining through openings in clouds or between other objects such as mountains, these columns of sunlit scattering particles are separated by darker shadowed volumes. Despite seeming to converge toward the light source, the rays are essentially parallel shafts of sunlit and shadowed particles. Their apparent convergence is a visual illusion from linear perspective. This illusion is the same as railway lines' or long hallways' appearing to converge at a distant vanishing point.

The scattering particles that make crepuscular rays visible can be air molecules or particulates.

The name comes from their frequent occurrences during twilight hours (those around dawn and dusk), when the contrasts between light and dark are the most obvious. Crepuscular comes from the Latin word "crepusculum", meaning twilight.

Crepuscular rays usually appear orange because 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. Particles in the air scatter short wavelength light (blue and green) through Rayleigh scatteringmuch more strongly than longer wavelength yellow and red light.

At sunset it is common to see rays or beams of sun light radiating from the sun. The first thing to stress about crepuscular rays is that they are actually parallel beams of light, and not diverging as they appear. This is an illusion caused by perspective. The sun is so far away that the light reaching the earth is fairly well collimated and obstructions such as clouds or mountains cause bright beams of light, or darks shadows, in the atmosphere which are very close to parallel and just appear to converge or diverge. The further away something is, the smaller it looks. This is what causes the edges of a straight road or railway tracks to look like they converge in the distance. This is called perspective.

As mentioned above crepuscular rays can be either beams of light or dark shadows in the atmosphere. In the case of beams of light, they can be seen due to the air they pass through scattering light. Thus the more air they pass through the brighter they look. This is why they are more prominent at the horizons and when the sun is low. When looking for crepuscular rays overhead you are looking directly across the beam, not along it, and will see less scattered light. In the case of shadows they can be seen because of all the air around them scattering light.