Two sources P and Q produce notes of frequency 660 Hz each. A listener moves from P to Q with a speed of 1 ms⁻¹. If the speed of sound is 330 m/s, then the number of beats heard by the listener per second will be

Options

(a) zero
(b) 4
(c) 8
(d) 2

Correct Answer:

4

Explanation:

∆f / f = v / C
(beats) /2 / f = v / C
Beats = 2 fv / C = 4