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CMC Medical CMC-Medical VELLORE Solved Paper-2009

  • question_answer
    Two sources are at a finite distance apart. They emit sound of wavelength\[\lambda \]. An observer situated between them on line joining the sources, approaches towards one source with speed u, then the number of beats heard per second by observer will be

    A)  \[\frac{2u}{\lambda }\]                               

    B)  \[\frac{u}{\lambda }\]

    C)  \[\frac{u}{2\lambda }\]                               

    D)  \[\frac{\lambda }{u}\]

    Correct Answer: A

    Solution :

                    \[{{n}_{1}}=\left( \frac{v+u}{v} \right)n\] and \[{{n}_{2}}=\left( \frac{v-u}{v} \right)n\] Number of beats per second \[x={{n}_{1}}-{{n}_{2}}\] \[=\left( \frac{v+u}{v} \right)n-\left( \frac{v-u}{v} \right)n\] \[=\left( \frac{v+u-v+u}{v} \right)n\] \[=2u\left( \frac{n}{v} \right)=\frac{2u}{\lambda }\]


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