What is the primary function of a radar gun in speed detection?

The primary function of a radar gun in speed detection is to measure the speed of moving vehicles. This device utilizes the Doppler effect, where the frequency of a radar signal changes if the object is moving towards or away from the radar source. As a vehicle approaches, the frequency of the reflected radar waves is compressed, indicating it is moving closer and thus allowing the gun to calculate its speed. Conversely, if the vehicle is moving away, the frequency is elongated. This speed measurement is crucial for law enforcement and traffic monitoring to ensure compliance with speed limits and enhance road safety.

The other choices refer to different functions unrelated to the primary purpose of a radar gun, thereby clarifying that the correct response specifically and accurately reflects the key role of radar technology in speed detection.