Radar, or radio detection and ranging, is a physical science and engineering technique that measures the range, angle, and velocity of objects by transmitting electromagnetic signals and analyzing the time delay and intensity of the reflected echoes. The principle relies on emitting pulsed radio waves and calculating the distance to a target by measuring the time elapsed between transmission and reception. By analyzing the Doppler shift of the returned signal, the system can determine the target's rate of change of distance from the source. Modern applications utilize varying frequencies and processing methods to achieve precise measurements, enabling uses ranging from atmospheric monitoring to industrial navigation and geological surveying.