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WB JEE Medical WB JEE Medical Solved Paper-2008

  • question_answer
    A car moving with a velocity of 36 km/h crosses a siren of frequency 500 Hz. The apparent frequency of siren after passing it will be

    A)  520 Hz                 

    B)  485 Hz

    C)  540 Hz                                 

    D)  460 Hz

    Correct Answer: B

    Solution :

                     Given that, velocity of the car \[=\frac{3600\,m}{3600\,s}=10\,m/s\] \[{{v}_{emitted}}=10\,m/s\] \[{{v}_{sound}}=330\,m/s\] We know that \[{{v}_{obs}}={{v}_{emitted}}\frac{({{v}_{sound}}-{{v}_{obs}})}{{{v}_{sound}}}\] Hence, observed frequency \[{{v}_{obs}}=500\frac{330-10}{330}\] \[\Rightarrow \]               \[{{v}_{obs}}=485\,Hz\]


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