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photomultiplier:see photoelectric cellphotoelectric cell
device whose electrical characteristics (e.g., current, voltage, or resistance) vary when light is incident upon it. The most common type consists of two electrodes separated by a light-sensitive semiconductor material.
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photomultiplier(foh-toh-mul -tă-plÿ-er) (photomultiplier tube; phototube) An electronic device used to convert a low-intensity light signal into an electrical signal and to amplify this signal very considerably. It contains a photocathode from which electrons are liberated by the incident light photons. The electrons are accelerated down an evacuated tube by a series of positively charged electrodes to which an increasingly high potential is applied. At each electrode a number of additional electrons are released by each impacting electron (by secondary emission). The electrons are all collected at the final electrode in the chain, which is held at a very high potential, and a large current pulse is produced.