Question

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

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

Answer 1

Answer: (A)

$\lambda=\frac{ v }{ n }=\frac{330}{330}=1\, m =100\, cm$
for first resonance length of air column
$\ell=\frac{\lambda}{4}=25\, cm$
second resonance $\ell_{2}=\frac{3 \lambda}{4}=75\, cm$
third resonance $\ell_{3}=\frac{5 \lambda}{4}=125\, cm$ which is not possible
minimum length of water column
$=120-75=45\, cm$