Question:
In a resonance tube experiment when the tube is filled with water up to height of $17.0 \mathrm{~cm}$ from bottom, it resonates with a given tuning fork. When the water level is raised the next resonance with the same tuning fork occurs at a height of $24.5 \mathrm{~cm}$. If the velocity of sound in air is $330 \mathrm{~m} / \mathrm{s}$, the tuning fork frequency is:
Correct Option: , 3
Solution:
$\Rightarrow \lambda=2\left(l_{2}-l_{1}\right) \Rightarrow 2 \times(24.5-17)$
$\Rightarrow 2 \times 7.5=15 \mathrm{~cm}$
$\& v=f \lambda \Rightarrow 330=\lambda \times 15 \times 10^{-2}$
$\lambda=\frac{330}{15} \times 100 \Rightarrow \frac{1100 \times 100}{5}$
$\Rightarrow 2200 \mathrm{~Hz}$