WBJEE 2014 Physics Solved Paper

A car moving with a speed of 72 km−hour–1 towards a roadside source that emits sound at a frequency of 850 Hz. Thecar driver listens to the sound while approaching the source and again while moving away from the source aftercrossing it. If the velocity of sound is 340 ms–1,the difference of the two frequencies, the driver hears in