Any of several devices that produce an electric signal in response to exposure to electromagnetic radiation. The original photocells utilized photoemission from a photosensitive cathode (photocathode). The electrons emitted are attracted to an anode. A positive potential on the anode enables a current to flow through an external circuit, the current being proportional to the intensity of the illumination on the cathode. The electrodes are enclosed in an evacuated glass tube (see also photomultiplier).
More modern light-sensitive devices utilize the photoconductive effect and the photovoltaic effect (see photoelectric effect; photodiode; phototransistor; solar cell).
Photoelectric cells.
A device that gives an electrical output in response to light; also known as a photocell. It may be photovoltaic, in which case the light generates an electric current, a photoconductive cell, or a photomultiplier. Only the last two are sensitive enough to be used in astronomy.
Alternative name for photocell.
See photocell.
- position vector
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- positive displacement pump
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- positive fragment
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- positive glow
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- positive inversion
- positive ion
- positive law/positive theology
- positive lens
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- positively oriented