JEE Main · 2009 · 12 Apr 2009 · Offline · Waves & Sound

Three sound waves of equal amplitudes have frequencies

(v - 1), v, (v + 1)

. They superpose to give beats. The number of beats produced per second will be

(A)4
(B)3
(C)2✓ Correct
(D)1

Answer: (C)

Solution

Beats arise from the spread of frequencies present, and the number heard per second is fixed by the difference between the highest and lowest. Here that difference is

(v + 1) - (v - 1) = 2

, so two beats are produced each second.

JEE Main · 2009 · 12 Apr 2009 · Offline · Single correct option

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