NEET Physics Wave Mechanics NEET PYQ-Wave Mechanics

  • question_answer
    Two sound waves with wavelengths 5.0 m and 5.5 m respectively, each propagate in a gas with velocity 330 m/s. We expect the following number of beats per second:                                                          [AIPMT (S) 2006]

    A) 12      

    B)                   0        

    C) 1        

    D)                   6

    Correct Answer: D

    Solution :

    Let \[{{\lambda }_{1}}=5.0\,m,\,v=330\,m/s\] and \[{{\lambda }_{2}}=5.5\,m\]
                The relation between frequency, wavelength and velocity is given by
                            \[v\,=n\,\lambda \]
    \[\Rightarrow \]   \[n=\frac{v}{\lambda }\]                        ...(i)
    The frequency corresponding to wavelength \[{{\lambda }_{1}},\]
    \[{{n}_{1}}=\frac{v}{{{\lambda }_{1}}}=\frac{330}{5.0}=66\,Hz\]
    The frequency corresponding to wavelength \[{{\lambda }_{2}},\]
    \[{{n}_{2}}=\frac{v}{{{\lambda }_{2}}}=\frac{330}{5.5}=60\,Hz\]
    Hence, no. of bears per second
                \[={{n}_{1}}-{{n}_{2}}\]
                \[=66-60\]
                \[=6\]


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