A photoelectric cell is a device that releases electricity when a beam of light falls on it. A good example of a practical application of this cell is the automatic door which automatically opens when a person approaches it.
When a person or an object goes near a door, to which an electric ‘eye’ is connected, a beam of light is cut off due to the presence of the approaching object. As the person continues to Walk, the beam of light is back again which strikes the photoelectric cell. Due to this the cell sends out an electric current that swings the door open. The same principle can be used to set off a burglar alarm.
