Wave Mechanics Question 894

Question: Beats are produced by two waves given by $ y _{1}=a\sin 2000,\pi t $ and $ y _{2}=a\sin 2008,\pi t $ . The number of beats heard per second is

[CPMT 1990; DCE 1999]

Options:

A) Zero

B) One

C) Four

D) Eight

Show Answer

Answer:

Correct Answer: C

Solution:

Number of beats per second = $ n _{1}\tilde{\ }n _{2} $

$ {\omega _{1}}=2000\pi =2\pi n _{1} $

Therefore n1 = 1000 and $ {\omega _{2}}=2008\pi =2\pi n _{2} $

Therefore n2 = 1004 Number of beats heard per sec$ =1004-1000=4 $