| photometer | <apparatus, physics> An instrument for measuring the intensity of light, or, more especially, for comparing the relative intensities of different lights, or their relative illuminating power. Origin: Photo: cf. F. Photometre. (24 Mar 1998) |
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| photoelectric | <physics> Acting by the operation of both light and electricity. Said of apparatus for producing pictures by electric light or electronic effects produced by the action of light. See: photoelectric effect, photoelectric absorption. (21 Jun 2000) |
| photoelectric absorption | <chemistry, physics> The interaction of an X-ray photon with matter in which the incident photon is completely absorbed, giving up all its energy by displacing an outer shell electron. (05 Mar 2000) |
| photoelectric effect | <chemistry, radiobiology> The interaction of a photon with an atom, resulting in the absorption of the incident photon and the release of a bound electron from that atom with energy equal to the photon energy less the electron binding energy. (16 Dec 1997) |