The instrument used to detect the position and distance of an object is called radar. Bad weather, darkness and smoke do not affect the performance of radar. Radars are mostly used to determine the position, speed and distance of aircrafts and ships.
An echo is produced when sound waves are reflected after striking an object. Similarly, radio waves produce an echo when they get reflected after striking a surface. The invention of radar is based upon the same principle. This is called the echo principle.
The word RADAR stands for Radio Detection and Ranging. The first successful radar was developed by Robert Watson watt and his colleagues in 1930 in
The transmitter of radar sends short pulses of high frequency from a rotating antenna. Theses pulses are reflected back after striking an object and are received by a receiver. The screen of the radar shows the position of the object. The time taken b the wave in going from the transmitter of radar to the object and then after reflection back to the receiver is determined. When this interval of time is multiplied by the velocity of light, we get double the distance of the object from the radar. The display unit fixed in the radar shows half of this distance. Besides aero plane and ship control, radar has played an important role in missile control, transport control, army, weather forecast, spacecraft control, etc.