Radar guns are devices used to measure the speed of moving objects, commonly employed by law enforcement to monitor vehicle speeds. They work by emitting radio waves that bounce off the target and return to the device, allowing it to calculate the speed based on the frequency change of the returned waves, a principle known as the Doppler effect. These devices can be handheld or mounted on vehicles and are often used in speed enforcement on roads and highways. Radar guns are also utilized in various sports, such as baseball and tennis, to measure the speed of pitches and serves, respectively.