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JEE Main & Advanced Sample Paper JEE Main Sample Paper-45

  • question_answer
    A train moving with \[20\,\,m{{s}^{-1}}\] towards a stationary observer produces frequency of 440 Hz. The apparent frequency heard will be (\[v=330\,\,m{{s}^{-1}}\])

    A)  448 Hz          

    B)  455 Hz          

    C)  440 Hz                       

    D)  468 Hz

    Correct Answer: D

    Solution :

     Apparent frequency heard by stationary observer \[n'=n\,\left( \frac{V}{V-{{V}_{s}}} \right)\] Given, \[V=330\,m{{s}^{-1}},\,\,{{V}_{s}}=20\,m{{s}^{-1}}\]and n = 440 Hz \[\therefore \]    \[n'440\,\,\left( \frac{330}{330-20} \right)\] \[=468.38\approx \,468\,Hz\]


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