NEET AIPMT SOLVED PAPER SCREENING 2006

  • 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:                                                       

    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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