﻿ Two whistles A and B produce notes of frequencies 660 Hz and 596 Hz respectively. There is a listener at the midpoint of the line joining them. Both the whistle B and the listener start moving with speed 30 m/s away from whistle A. If speed of sound be 330 m/s, how many beats will be heard by the listener? : Kaysons Education

# Two Whistles A And B Produce Notes Of Frequencies 660 Hz And 596 Hz Respectively. There Is A Listener At The Midpoint Of The Line Joining Them. Both The Whistle B and The Listener Start Moving With Speed 30 M/s Away From Whistle A. If Speed Of Sound Be 330 M/s, How Many Beats Will Be Heard By The Listener?

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## Question

### Solution

Correct option is

4

Here, the whistle B and listener (both) are moving with same speed. Hence, there will be no change in the pitch of whistle B to the listener. Frequency of the note from A will be:

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Q10

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?