Question

A tuning fork of frequency $n$ is held near the open end of a tube, which is closed at the other end, and the length of the tube is adjusted until resonance occurs. If the two shortest lengths to produce resonance are $L_{1}$ and $L_{2}$ , then the speed of the sound is

• A. $n\left(\right.L_{2}-L_{1}\left.\right)$
• B. $\frac{n \left(L_{2} - L_{1}\right)}{2}$
• C. $4n\left(\right.L_{2}-L_{1}\left.\right)$
• D. $2n\left(\right.L_{2}-L_{1}\left.\right)$

Answer 1

Answer: (D)

$n= \, \frac{v}{4 L_{1}}$ and $n=\frac{3 v}{4 L_{2}}$
$\therefore v=4nL_{1}$ and $3v=4nL_{2}$
$ \, \, \, or \, 2v=4n\left(L_{2} - L_{1}\right)$
$ \, \, \, or \, \, v=2n\left(L_{2} - L_{1}\right)$