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Question:

Three sound waves of equal amplitudes have frequencies (n-1), n, (n+1). They superimpose to give beats. The number of beats produced per second will be?

2

1

3

4

Solution:

The formula for the beat frequency is
fb = f2 - f1
Where f1 and f2 are the frequencies of two waves.
Now
fb = f2 - f1
fb = (n+1) - (n-1)
fb = (n + 1 - n + 1)
fb = 2
Thus the number of beats produced per second will be 2.