1. Pertaining to the electric effects of light or other radiation.
2. Relating to, or produced by, the electrical effects of light, including the emission of electrons, the generation of a voltage, or a change in resistance.

A phototube with one or more dynodes (electrodes the primary function of which is secondary emission of electrons) between its photocathode (photosensitive surface that emits electrons when exposed to light or other suitable radiation) and the output electrode.

The electron stream from the photocathode is reflected off each dynode in sequence, with a secondary emission adding electrons to the stream at each reflection.

A photometer (instrument used for making measurements of light or electromagnetic radiation, in the visible range) which uses a photocell, a phototransistor, or a phototube to measure the intensity of light.

A colorimeter that uses a phototube or photocell, a set of color filters, an amplifier, and an indicating meter for quantitative determination of color.

1. A device that generates electrical energy from light energy, usually as a voltage or current.
2. An instrument which converts light into electrical energy or uses it to regulate a flow of current, often incorporated into automatic control systems for doors and lighting.
3. An electronic device having an electrical output that varies in response to incident radiation; especially, to visible light.
4. A small cathode-ray tube having a fluorescent pattern whose size varies with the voltage applied to the grid.

It is used in radio receivers to indicate accuracy of tuning and as a modulation indicator in some tape recorders.

5. An electric eye can operate a mechanism so as to open a door when its invisible beam is interrupted by the approach of a person and includes a photoelectric cell which is used as an automatic controlling appliance.

It is also used in motion pictures, television, and many other industries.

A phenomenon in which electrons are emitted from a material (generally a metal) when it is exposed to light with a given frequency.

The classical concept of light as a continuous wave could not account for this, and it was then explained by Einstein (1905) on the basis that light is a stream of separate particles.

This interpretation, and his subsequent elaboration of it, is said to have formed the basis for much of quantum mechanics.