shadow

The projection of shadows obviously follows the same laws as the projection of objects on a plane perpendicular to the line of regard and is therefore governed by the same laws as perspective (p 194). In dealing with shadows…we must distinguish between two questions…the first relates to the understanding of the physical causes of shadows, and the second to the ability to forsee the shapes thay may assume according to what shaped object they correspond to (p 195).

The portion of a visual field that is cut off from the illuminating source by an intervening object and therefore appears “darker’ i.e. has a reduced luminance. Examples include eclipses and phases of the moon; the adaptation to shade of plants and animals under a forest canopy; and the instinctive startle response of organisms to a moving shadow.