The fundamental frequency of a closed organ pipe of length 20 cm is equal to the second overtone of an organ…
Solution
\(n_c=\frac{V}{4 l}\)
For open organ pipe,
\(n_0=\frac{V}{2 l^{\prime}}\)
For the second overtone of an open organ pipe,
\(\begin{aligned}
& n^{\prime}=3 n_0=\frac{3 V}{2 l^{\prime \prime}} \\
& n_c=n^{\prime} \\
& \frac{V}{4 l}=\frac{3 V}{2 l^{\prime}} \\
& l^{\prime}=6 l=6 \times 20 \\
& l^{\prime}=120 \mathrm{~cm}
\end{aligned}\)
Asked in: NEET 2015 (Phase 1)