KVPY Sample Paper KVPY Stream-SX Model Paper-7

  • question_answer
    A transverse propagating wave is described by \[y=A\sin 2\pi \left( Bt-\frac{x}{c} \right)\]. If maximum particle speed is exactly equal to wave speed, then value of \[\frac{C}{A}\] is

    A) \[\pi \]                           

    B)  \[2\pi \]

    C) \[\frac{\pi }{2}\]                        

    D) \[\frac{B}{2\pi }\]

    Correct Answer: B

    Solution :

    Comparing given equation with
    \[y=A\sin 2\pi \left( \frac{t}{T}-\frac{x}{\lambda } \right)\]
    We have, \[T=\frac{1}{B}and\lambda =c\]
    So, \[f=frequency=\frac{1}{T}=B\]
    Hence, wave speed, \[{{\upsilon }_{wave}}=f\lambda \]
    \[\Rightarrow \,\,\,\,\,\,\,{{\upsilon }_{wave}}=BC\]
    Also, particle's maximum speed,
    \[{{\upsilon }_{\max }}=A\omega =A\left( \frac{2\pi }{T} \right)\]
    \[\Rightarrow \,\,\,\,\,\,\,\,{{\upsilon }_{\max }}=A\left( 2\pi B \right)\]
    Now given, \[{{\upsilon }_{wave}}={{\upsilon }_{\max }}\]
    \[\Rightarrow BC=2\pi AB\]
    \[\Rightarrow \frac{C}{A}=2\pi \]


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