Question

The number of beats heard per second if there are three sources of sound of frequencies (n - 1), n and (n + 1) of equal intensities sounded together is

• A. 2
• B. 1
• C. 4
• D. 3

Answer 1

The correct option is A 2

Sound waves are having equal amplitudes and have frequencies $n-1,n$ and $n+1$ respectively. For finding the beat frequency we need to consider the maximum difference.

Thus maximum number of beats $=(n+1)-(n-1)=2$

Hence the maximum number of beats per second is $42$