Shadow

A shadow is a dark (real image) area where light from a light source is blocked by an opaque object. It occupies all of the three-dimensional volume behind an object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or a reverse projection of the object blocking the light.Non-diffuse lighting in outer space causes deep shadowsReversed text in shadowSutro Tower casts a 3D fog shadowThis photo of jasmine flowers has only soft shadows cast by diffused lightClouds and shadows over the Mediterranean SeaShadow cast by vapour trail of passing aircraftTree shadowShadow on the CastleLong shadow of a dead tree with its branches on dry fields, late afternoon A shadow is a dark (real image) area where light from a light source is blocked by an opaque object. It occupies all of the three-dimensional volume behind an object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or a reverse projection of the object blocking the light. A point source of light casts only a simple shadow, called an 'umbra'. For a non-point or 'extended' source of light, the shadow is divided into the umbra, penumbra and antumbra. The wider the light source, the more blurred the shadow becomes. If two penumbras overlap, the shadows appear to attract and merge. This is known as the Shadow blister effect.