Question

A cylindrical tube $(L=120cm$.) is resonant with a tuning fork of frequency $330Hz$. If it is filling by water then to get resonance minimum length o water column is $(V_{\text{air }}=330m/s$ )

• A. 45 cm
• B. 60 cm
• C. 25 cm
• D. 20 cm

Answer 1

Answer: (A)

$\lambda =\frac{v}{n}=\frac{330}{330}=1m=100cm$
for first resonance length of air column
$\ell =\frac{\lambda }{4}=25cm$
second resonance ${\ell }_2=\frac{3\lambda }{4}=75cm$
third resonance ${\ell }_3=\frac{5\lambda }{4}=125cm$ which is not possible
minimum length of water column
$=120-75=45cm$