A tuning fork of frequency ' $n$ ' is held near the open end of tube which is closed at the other end and…
A tuning fork of frequency ' $n$ ' is held near the open end of tube which is closed at the other end and the length are adjusted until resonance occurs. The first resonance occurs at length $\mathrm{L}_1$ and immediate next resonance occurs at length $\mathrm{L}_2$. The speed of sound in air is
For first resonance $\mathrm{L}_1=\frac{\lambda}{4}$
For second resonance $\mathrm{L}_2=\frac{3 \lambda}{4}$
$\begin{aligned}
& \therefore \mathrm{L}_2-\mathrm{L}_1=\frac{\lambda}{2} \text { or } \lambda=2\left(\mathrm{~L}_2-\mathrm{L}_1\right) \\
& \mathrm{V}=\mathrm{n} \lambda=2 \mathrm{n}\left(\mathrm{L}_2-\mathrm{L}_1\right)
\end{aligned}$