JCECE Medical JCECE Medical Solved Paper-2008

  • question_answer
    An observer moves towards a stationary source of sound, with a velocity one-fifth of the  velocity of sound. What is the percentage increase in the apparent frequency?

    A)  Zero            

    B)  0.5%

    C)  5%             

    D)  20%

    Correct Answer: D

    Solution :

     Given \[{{v}_{o}}=\frac{v}{5}\Rightarrow {{v}_{o}}=\frac{320}{5}=64\,m/s\] When observer moves towards the stationary source, then \[n'=\left( \frac{v+{{v}_{o}}}{v} \right)n\] \[n'=\left( \frac{320+64}{320} \right)\] \[n'=\left( \frac{384}{320} \right)n\] \[\frac{n'}{n}=\frac{384}{320}\] Hence, percentage increase \[\left( \frac{n'-n}{n} \right)=\left( \frac{384-320}{320}\times 100 \right)%\] \[=\left( \frac{64}{320}\times 100 \right)%=20%\]


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