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MGIMS WARDHA MGIMS WARDHA Solved Paper-2010

  • question_answer
    A stationary police car sounds a siren with a frequency of 990 Hz. If the speed of sound is 330 m/s, an observer, driving towards the car with a speed of 33 m/s, will hear a frequency of

    A)  891 Hz                                 

    B)  900 Hz

    C)  1089 Hz                               

    D)  1100 Hz

    Correct Answer: C

    Solution :

                     From Dopple?s effect the perceived frequency \[f'\]is given by \[f'=f\left( \frac{v+{{v}_{0}}}{v} \right)\] Given\[f=990\text{ }Hz,\text{ }v=300\text{ }m/s,\text{ }{{v}_{0}}=33\text{ }m/s\] \[\therefore \]  \[f'=990\left( \frac{330+33}{330} \right)\]                 \[=990\times \frac{363}{330}=1089\,Hz\]


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