How does a photoelectric cell produce an electric current when illuminated?

A photoelectric cell, or photocell, produces an electric current through the photoelectric effect, which involves the emission of electrons from a material when it is exposed to light or other electromagnetic radiation.12

The device typically consists of a photosensitive cathode and an anode housed within an electron tube. When light strikes the cathode, it provides enough energy to eject electrons from the material's surface. These emitted electrons are then attracted to the positively charged anode, creating a flow of electricity.32

The resulting current is proportional to the intensity of the incident light. In darkness, no electrons are emitted, and no current flows. This mechanism allows the cell to act as a switch in control systems; when a beam of light is interrupted, the circuit is broken, which can trigger a relay to operate various mechanisms, such as opening doors or activating alarms.321