Question

In an experiment to determine the velocity of sound in air at room temperature using a resonance tube, the first resonance is observed when the air column has a length of $20.0cm$ for a tuning fork of frequency $400Hz$ is used. The velocity of the sound at room temperature is $336m{s}^{–1}$. The third resonance is observed when the air column has a length of cm

Answer 1

$400=\frac{v}{4(L_1+e)}...\left(i\right)$
$400=\frac{5v}{4(L_2+e)}...\left(ii\right)$
$\Rightarrow L_1+e=\frac{\lambda }{4}=21cm$
$L_2+e=\frac{5\lambda }{4}=105cm$
$\Rightarrow e=1cm\&L_2=104cm$