shadow

shadow

1. the dark portions of a picture

2. Med a dark area on an X-ray film representing an opaque structure or part

3. (in Jungian psychology) the archetype that represents man's animal ancestors

4. Brit designating a member or members of the main opposition party in Parliament who would hold ministerial office if their party were in power

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shadow [′shad·ō]

(optics)

A region of darkness caused by the presence of an opaque object interposed between such a region and a source of light.

(physics)

A region which some type of radiation, such as sound or x-rays, does not reach because of the presence of an object, which the radiation cannot penetrate, interposed between the region and the source of radiation.

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Shadow

A region of darkness caused by the presence of an opaque object interposed between such a region and a source of light. A shadow can be totally dark only in that part called the umbra, in which all parts of the source are screened off. With a point source, the entire shadow consists of an umbra, since there can be no region in which only part of the source is eclipsed. If the source has an appreciable extent, however, there exists a transition surrounding the umbra, called the penumbra, which is illuminated by only part of the source. Depending on what fraction of the source is exposed, the illumination in the penumbra varies from zero at the edge of the full shadow to the maximum where the entire source is exposed. The edge of the umbra is not perfectly sharp, even with an ideal point source, because of the wave character of light. See Diffraction

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(language)

SHADOW - A syntax-directed compiler written by Barnett and Futrelle in 1962. It was the predecessor to SNOBOL(?) [Sammet 1969, p. 448, 605].