Applications of photoelectric effect
Applications of photoelectric effect-Photo-emissive cells– they are made up of two electrodes enclosed in a glass bulb (evacuated or containing inert gas at low temperature). Thecathode is a curved metal plate while the anode is normally a single metal rod)-They are used mostly in controlling lifts (doors) and reproducing the sound track in a film.-Photoconductive cells – some semi-conductors such as cadmium sulphide (cds) reduces their resistance when light is shone at them (photoresistors). Other devices such as photo-diodes and phototransistors block current when the intensity of light increases.-Photo-conductive cells are also known as light dependent resistors (LDR) and are used in alarm circuits i.e. fire alarms, and also in cameras as exposure metres.-Photo-voltaic cell– this cell generates an e.m.f using light and consists of a copper disc oxidized on one surface and a very thin film of gold isdeposited over the exposed surfaces (this thin film allows light). The current increases with light intensity. They are used in electronic calculators, solar panels etc.