A cathode that emits electrons when light falls upon it, as a result of the photoelectric effect. Seephotoelectric cell.
Astronomy
The light-sensitive surface of a photomultiplier. It is a coating of a material such as caesium, rubidium, or potassium applied to the inside of a clear window of an evacuated tube.
Electronics and Electrical Engineering
A cathode that emits electrons as a result of the photoelectric effect.