Shadows

Shadows are regions where light is blocked by an opaque object, resulting in a darker area on a surface or in space. They appear whenever at least one light source is obscured. A shadow produced by an opaque body on a surface is called a cast shadow; the region behind the object in line with the light source is also shadowed, though it may be faint.

The shape and intensity of a shadow depend on the light source and geometry. If the light source is effectively a single point, the shadow edges are sharp; with an extended light source, such as the sun or a lamp with a finite size, the shadow comprises an inner dark region called the umbra and a surrounding lighter region called the penumbra. The relative distance between the light source, the object, and the illuminated surface also affects the size and softness of the shadow: moving the object farther from the surface can increase the shadow’s apparent size and soften its edges.

In daily life, shadows reveal the arrangement of objects and light, convey depth, and indicate time of day. They also play a central role in visual arts, where shading and silhouettes help express shape, texture, and mood. Shadow phenomena include colored shadows created by multiple light sources and soft shadows under bright, diffuse lighting, as well as hard shadows under strong, small light sources.