1) Cathode 
A photocathode is a negatively charged electrode in a light detection device such as a photomultiplier or phototube that is coated with a photosensitive compound. When this is struck by a quantum of light (photon), the absorbed energy causes electron emission due to the photoelectric effect. ==Uses== For many years the photocathode was the only pr...
an element of a photoelectric cell (q.v.) that emits electrons when struck by light, making possible the flow of electric current through the ... [3 related articles]
a cathode that functions by photoelectric emissiona semi-transparent photo-sensitive electrode, in certain types of camera tube, on which the optical image is focused and whose elements emit electrons under the influence of lightmetallic or semiconducting layer designed for efficient photoemission of electrons and used in a photoelectric detectoran electrode in a vacuum tube made of a material that emits electrons when light is incident upon it
[n] - a cathode that emits electrons when illuminated
noun a cathode that emits electrons when illuminated