Range is the shortest distance between a source and a destination up to which the signal is received with sufficient strength
A stationary source emits sound of frequency f0=492 Hz. The sound is reflected by a large car approaching the source with a speed of 2 ms−1. The reflected signal is received by the source and superposed with the original. The beat frequency of the resulting signal is Hz. (Given that the speed of sound in air is 330 ms−1 and the car reflects the sound at the frequency it has received).