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Question: Answered & Verified by Expert
If the seventh harmonic of a closed organ pipe is in unison with fourth harmonic of an open organ pipe, then the ratio of length of closed pipe to that of open pipe is
PhysicsWaves and SoundTS EAMCETTS EAMCET 2023 (13 May Shift 1)
Options:
  • A $4: 7$
  • B $7: 4$
  • C $8: 7$
  • D $7: 8$
Solution:
1084 Upvotes Verified Answer
The correct answer is: $7: 8$
For closed organ pipe
$$
\mathrm{f}_{\mathrm{c}}=\frac{\mathrm{nv}}{4 \mathrm{I}_{\mathrm{c}}}=\frac{7 \mathrm{v}}{4 \mathrm{I}_{\mathrm{c}}}
$$

For open organ pipe
$$
\begin{aligned}
& f_o=\frac{n v}{21_o}=\frac{4 v}{21_o} \\
& \because f_c=f_o \\
& \frac{7 v}{41_c}=\frac{4 v}{21_o} \Rightarrow \frac{1_c}{1_o}=\frac{7}{8}
\end{aligned}
$$

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