How do police radar speed guns work?
A radar gun works off the Doppler effect. You hear the Doppler effect often when you’re passed by a train or an ambulance. The sound suddenly gets lower when the train passes you. That’s because the waves of sound are more stretched out: between two successive peaks of the sound wave, the vehicle has moved further away, lowering the frequency. The same thing happens with radar waves. They send out a radar beam at one frequency, and it bounces back to them off your car at another frequency. The difference in the frequencies lets them know how fast you’re going. They’re limited by how effectively they can detect the radar. The cheap ones have a range of half a mile. The good ones have a range of more than a mile. The top of the line speed detectors are actually lasers rather than radars. It’s the same effect (lasers are just a different frequency) but they make a narrower beam. That means they know they’re bouncing it off just one car and not being confused by the bounce from multiple ca
