Common Doppler radar systems use radio waves.
A radar transmitter sends electromagnetic waves toward a target, and the receiver analyzes the returning signal. If the target is moving toward or away from the radar, the returned frequency differs slightly from the transmitted frequency. That Doppler shift allows the system to estimate radial velocity—the component of motion along the radar’s line of sight.
Doppler radar is used in weather observation, aviation, speed measurement, and military tracking. Weather radars can use frequency shifts from reflected signals to estimate how precipitation is moving, including wind patterns inside storms. A target moving directly toward or away from the antenna produces the largest shift; motion across the beam produces little or no radial shift.
Radio waves are often confused with visible light because both are electromagnetic radiation. They are not the same band of the spectrum: radio waves have much longer wavelengths and lower frequencies. X-rays and gamma rays are electromagnetic too, but they are not the standard waves used by ordinary Doppler radar.