NEET Physics Wave Mechanics NEET PYQ-Wave Mechanics

  • question_answer
    A transverse wave is represented by the equation
    \[y={{y}_{0}}\sin \frac{2\pi }{\lambda }(vt-x)\]
    For what value of \[\lambda \] is the maximum particle velocity equal to two times the wave velocity?    [AIPMT 1998]

    A)        \[\lambda =2\,\pi {{y}_{0}}\]   

    B)       \[\lambda =\frac{\pi {{v}_{0}}}{3}\]

    C)  \[\lambda =\frac{\pi {{y}_{0}}}{2}\]    

    D)       \[\lambda =\pi {{y}_{0}}\]

    Correct Answer: D

    Solution :

    The given equation is
    \[y={{y}_{0}}\sin \,\frac{2\pi }{\lambda }(vt-x)\]             .....(i)
    In the wave equation v is the particle velocity.
    Differentiating Eq. (i) with respect to time,
    \[u=\frac{dy}{dx}={{y}_{0}}\frac{2\pi v}{\lambda }\cos \frac{2\pi }{\lambda }(vt-x)\]
    Maximum particle velocity, \[{{u}_{\max }}={{y}_{0}}\frac{2\pi v}{\lambda }\]
    Now it is given that,
                maximum particle velocity \[=2\times \] wave velocity
    or         \[{{y}_{0}}\frac{2\pi v}{\lambda }=2v\]
    or         \[\lambda =\pi {{y}_{0}}\]


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