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JEE Main & Advanced Physics Wave Mechanics Question Bank Doppler's Effect

  • question_answer
    When an engine passes near to a stationary observer then its apparent frequencies occurs in the ratio 5/3.  If the velocity of engine is                                                 [MP PMT 2003]

    A)            540 m/s                                  

    B)            270 m/s

    C)            85 m/s                                    

    D)            52.5 m/s

    Correct Answer: C

    Solution :

               When engine approaches towards observer \[n'=n\,\left( \frac{v}{v-{{v}_{s}}} \right)\]                    when engine going away from observer \[{n}''=\left( \frac{v}{v+{{v}_{S}}} \right)n\]                    \[\therefore \] \[\frac{n'}{n''}=\frac{v+{{v}_{s}}}{v-{{v}_{s}}}\Rightarrow \frac{5}{3}=\frac{340+{{v}_{s}}}{340-{{v}_{s}}}\Rightarrow {{v}_{s}}=85\]\[m/s\].


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