An atmospheric phenomenon resulting from the scattering of sunlight by dust particles in the troposphere. Crepuscular rays are seen in twilight near sunset or sunrise, when the shadows cast by distant clouds give rise to a fan-like effect, the rays appearing to diverge from the Sun as a result of perspective. A similar effect is also seen when the Sun is behind dense convective clouds and the cloud edge casts shadows over sunlit areas away from the observer. An inverse effect is seen when bright sunbeams fall through small gaps in a sheet of cloud.