Question

A hollow metallic tube of length $L$ and closed at one end produce resonance with a tuning fork of frequency $n$. The entire tube is then heated carefully so that at equilbrium temperature its length changes by $\ell$. If the change in velocity $V$ of sound is $v$, the resonance will now be produced by tuning fork of frequency.

• A. $( V + v ) /[4( L +\ell)]$
• B. $( V + v ) /[4( L -\ell)]$
• C. $( V - v ) /[4( L +\ell)]$
• D. $( V - v ) /[4( L -\ell)]$

Answer 1

Answer: (A)

$n =\frac{ v }{4 \ell}$
By increasing temperature, velocity of sound $\&$ length both increases, so
$n=\frac{V+v}{4(L+\ell)}$