Question

Three sound waves of equal amplitudes have frequencies (υ – 1), υ, (υ + 1). They superpose to give beats. The number of beats produced per second will be

(a) 4 

(b) 3

(c) 2 

(d) 1.

Answer 1

(a) : The given sources of sound produce frequencies, (υ – 1), υ and (υ + 1).
For two sources of frequencies u₁ and υ₂,
y₁ = A cos2πυ₁t
y₂ = A cos2πυ₂t
Superposing, one gets