Manipal Engineering Manipal Engineering Solved Paper-2010

  • question_answer
    When the wavelength of sound changes from 1 m to 1.01 m, the number of beats heard are 4. The velocity of sound is

    A)  404 m/s                              

    B)  4.04 m/s

    C)  414 m/s              

    D)         400 m/s

    Correct Answer: A

    Solution :

    Let\[{{n}_{1}}\]and\[{{n}_{2}}\]be the frequencies of the two notes of wavelengths\[{{\lambda }_{1}}\]and\[{{\lambda }_{2}}\]. Here,     \[{{\lambda }_{1}}=1m,\,\,{{\lambda }_{2}}=1.01m\] If\[v\]is velocity of sound, then                 \[{{n}_{1}}=\frac{v}{1}\]and\[{{n}_{2}}=\frac{v}{1.01}\] If the number of beats produced per second is\[b\], then                 \[b={{n}_{1}}-{{n}_{2}}\]                 \[4=\frac{v}{1}-\frac{v}{1.01}\] \[\therefore \]  \[v=\frac{4.04}{0.01}=404\,\,m/s\]


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