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Question: Answered & Verified by Expert
The fundamental frequency of a closed organ pipe of length 20 cm is equal to the second overtone of an organ pipe open at both the ends. The length of the organ pipe open at both the ends is
PhysicsWaves and SoundJEE Main
Options:
  • A 80 cm
  • B 100 cm
  • C 120 cm
  • D 140 cm
Solution:
2681 Upvotes Verified Answer
The correct answer is: 120 cm
For closed organ pipe,
\(n_c=\frac{V}{4 l}\)
For open organ pipe,
\(n_0=\frac{V}{2 l^{\prime}}\)
For the second overtone of an open organ pipe,
\(\begin{aligned}
& n^{\prime}=3 n_0=\frac{3 V}{2 l^{\prime \prime}} \\
& n_c=n^{\prime} \\
& \frac{V}{4 l}=\frac{3 V}{2 l^{\prime}} \\
& l^{\prime}=6 l=6 \times 20 \\
& l^{\prime}=120 \mathrm{~cm}
\end{aligned}\)

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