Radar

Radar is a device that transmits radio waves to detect and/or locate the position and velocity of a distant object such as an aeroplane. The etymology of the name is an acronym of radio detection and ranging. Radar works by picking up a reflection of the radio waves which it can then use to calculate the position, direction, and speed of the object. In systematic terms, radar is a simple concept which consists of a transmitter and receiver, but it has proved invaluable in wartime, especially during the Battle of Britain in 1940.