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Physics · PYQ NEET UG 2018
हिन्दीThe fundamental frequency in an open organ pipe is equal to the third harmonic of a closed organ pipe. If the length of the closed organ pipe is \( 20\text{ cm} \), the length of the open organ pipe is
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Correct answer · Option A
\( 13.2\text{ cm} \)
Explanation
Frequency of open pipe fundamental \( f_o = \frac{v}{2l_o} \). Third harmonic of closed pipe \( f_c = \frac{3v}{4l_c} \). Given \( f_o = f_c \implies \frac{v}{2l_o} = \frac{3v}{4l_c} \implies l_o = \frac{2}{3} l_c = \frac{2}{3} \times 20 = 13.33\text{ cm} \approx 13.2\text{ cm} \).
