Question

Two waves of wavelength 99cm and 100cm both travelling with velocity 396m/s are made to interfere. The number of beats produced by them per second is?

(a) 1

(b) 2

(c) 4

(d) 8

The question was asked in an interview.

The question is from Travelling Waves in division Waves of Engineering Physics I

Answer 1

Correct answer is (c) 4

To elaborate: Beat frequency=v[(1/ʎ1)-(1/ʎ2)]

=396[(1/0.99)-(1/1)]=4Hz.