Brilliant beams of light extending from clouds are often seen during the early morning or early evening when the sun is shining. This phenomenon is known as crepuscular rays, as it occurs during crepuscular hours – those around dusk and dawn. Rays of light can change direction when they encounter small particles suspended in the atmosphere. This changing of directions is called scattering. A cloud between you and the sun can block some but not all of the sun’s light. The darker regions are the shadowed area of the cloud. Where the light peeks through the object, scattering illuminates its path from the sun to your eyes. This creates beams in the sky. These beams appear to converge toward the sun; however, this is an illusion, similar to the impression that the rails on train tracks appear to come together in the distance.
Mountains can also generate crepuscular rays when they shadow the sun. You also can see this effect in buildings with tall ceilings when the sunlight shines directly through the windows, provided there is enough haze or dust particles in the building so that the sunlight can be scattered towards you. When crepuscular rays spread down to the ground, they are called Jacob's Ladder, a “ladder to heaven”.
You can occasionally see beams of light converging on the opposite side of the sun, or the anitsolar point. These rays are called anticrepuscular rays and are similar to crepuscular rays.