In this technique, the Probert–Jones equation sets the backscattered power proportional to the reflectivity factor Z. Before it was used for diathermic heating, the cavity magnetron was developed for use in this technique. FM is often combined with the “continuous-wave” form of this technique, which predates a variant that measures the phase shift between pulses to observe features like hook echoes. (-5[1])The velocity of water droplets can be measured via the Doppler effect in this technique, which is able to detect (-5[1])supersonic V-2 rockets. The NWS uses this technique to track (10[1])weather (-5[1])patterns. (10[1]-5[1])For 10 points, (10[1])name this technique that uses radio waves (10[1])to find the distance to an object. ■END■ (10[4])