Yeah, it uses radio frequencies. RaDAR stands for “Radio Detection And Ranging”. It uses radio waves (usually in the microwave bandwidth) to detect things. Basically, since those radio waves are affected by the Doppler effect, you can have a computer do some math to determine the speed of whatever those waves reflected off of. Because the Doppler effect changes a wave based on how fast an object is moving relative to an observer. So if you’re a stationary observer, you can figure out how fast an object is moving relative to yourself, purely based on how much that moving object changes the waves you’re reflecting off of it.