## Question

Two sources *A* and *B* are sounding notes of frequency 680 Hz. A listener moves from *A* to *B* with a constant velocity *u*. If the speed of sound is 340 m/s, what must be the value of *u* so that he hears 10 beats per sec?

### Solution

2.5 m/s

Apparent frequency due to source *A*,

Apparent frequency due to source *B*

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