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RAJASTHAN PMT Rajasthan - PMT Solved Paper-2003

  • question_answer
    A source emitting a note of frequency 240 Hz is moving towards an observer with a speed of 20 m/s. If the observer also moves with a speed of 20 m/s towards the source, the apparent frequency heard by observer is (velocity of sound = 340 m/s)

    A)  270 Hz                 

    B)         240 Hz

    C)  268 Hz                 

    D)         360 Hz

    Correct Answer: A

    Solution :

    When source and observer move towards each other, the apparent frequency,  \[n\frac{\upsilon +{{\upsilon }_{0}}}{\upsilon -{{\upsilon }_{s}}}n\] Here      \[{{\upsilon }_{0}}={{\upsilon }_{s}}=20\,\,m/s\]                                   \[\upsilon =240\,Hz\] \[\therefore \]  \[n=\frac{340+20}{340-20}\times 240Hz\]                                     \[=\frac{260}{320}\times 240Hz\]                                     \[=270\,Hz.\]


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