How does a speed radar gun work?


Quick Answer

A radar gun works by bouncing a narrow band radio signal off of a moving object. The velocity of the object affects the frequency at which the signal is reflected due to the Doppler effect. By measuring the frequency change, the radar gun can calculate the velocity of the object.

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Full Answer

Police still use radar for speed detection, but since the early 21st century, handheld speed detection guns have more often utilized a technology called LIDAR. LIDAR guns fire an infrared laser pulse at a vehicle, and they measure the amount of time it takes for the reflected pulse to return. By taking hundreds of readings per second, the gun can calculate the rate at which the vehicle's location is changing.

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