An open organ pipe and a closed organ pipe have the frequency of their first overtone identical. The ratio…

An open organ pipe and a closed organ pipe have the frequency of their first overtone identical. The ratio of length of open pipe to that of closed pipe is
  1. 3:4
  2. 1:2
  3. 2:1
  4. 4:3

Solution

$\frac{\ell_{0}}{\ell_{c}}=?$ $\begin{array}{ll}\text { For closed pipe } & n_{p}=n_{0}(2 p+1) \Rightarrow n_{l c}=n_{o}^{3} \\ \text { For open pipe } & n_{p}=n_{0}(p+1) \Rightarrow n_{l o}=n_{0}^{2}\end{array}$ $\begin{aligned} & n_{1 c}=3 n_{0}=\frac{3 V}{4 \ell_{c}} \\ & n_{10}=2 n_{0}=\frac{2 V}{2 \ell_{0}} \\ \therefore & \frac{3 V}{4 \ell_{c}}=\frac{2 V}{2 \ell_{0}} \\ \therefore & \frac{\ell_{0}}{\ell_{c}}=\frac{4}{3} \end{aligned}$

Asked in: MHT CET 2020 (16 Oct Shift 2)

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