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NEET Physics Wave Mechanics NEET PYQ-Wave Mechanics

  • question_answer
    The 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 cm, the length of the open organ pipe is                                          [NEET - 2018]

    A)  12.5 cm           

    B)  8 cm

    C)  13.2 cm           

    D)  16 cm

    Correct Answer: C

    Solution :

    [c] For closed organ pipe, third harmonic
    \[\text{=}\frac{3v}{4l}\]
    For open organ pipe, fundamental frequency
    \[=\frac{v}{2l'}\]
    Given,
    \[\frac{3v}{4l}=\frac{v}{2l'}\]
    \[\Rightarrow l'=\frac{4l}{3\times 2}=\frac{2l}{3}\]
    \[=\frac{2\times 20}{3}=13.33cm\]


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