Question

A tuning fork of frequency $340Hz$ is sounded above a cylindrical tube $1m$ long. Water is slowly poured into the tube .If the speed of sound is $340m{s}^{-1}$, at what levels of water in the tube will the sound of the tuning fork be appreciably intensified?

• A. $25cm,75cm$
• B. $20cm,80cm$
• C. $23cm,67cm$
• D. $40cm,80cm,$

Answer 1

Answer: (A)

$25cm,75cm$

The tuning fork is in resonance with a water column closed at one end:

$\therefore$ resonance will occur at lengths:

$H=\frac{nv}{4f}\times L$ for $n=1,3,5...$

Now, $H=\frac{n\times 340}{4\times 340}\times 100cm=n\times 25cm$

$H_1=25cm$, $H_2=75cm$