Wave Mechanics Beats Question 37

Question: A tuning fork gives 4 beats with 50 cm length of a sonometer wire. If the length of the wire is shortened by 1 cm, the number of beats is still the same. The frequency of the fork is

[MP PMT 2001]

Options:

A) 396

B) 400

C) 404

D) 384

Show Answer

Answer:

Correct Answer: A

Solution:

$ n\propto \frac{1}{l} $

Therefore $ n _{1}l _{1}=n _{2}l _{2} $

Therefore $ (n+4)49=(n-4)50\Rightarrow n=396 $