<P> A shadow is a dark 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 . </P> <P> 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 . </P>

Where is an objects cast shadow in relationship to the light source
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