JEE Main & Advanced Sample Paper JEE Main Sample Paper-25

  • question_answer
    Sound waves of frequency \[f=600\] Hz fall normally on a perfectly reflecting wall. The shortest distance from the wall at which all particles will have maximum amplitude of vibration will be (speed of sound \[=300\,m{{s}^{-1}}\])

    A)  \[\frac{7}{8}m\]                                   

    B)  \[\frac{3}{8}m\]

    C)  \[\frac{1}{8}m\]                                   

    D)  \[\frac{1}{4}m\]

    Correct Answer: C

    Solution :

    The wall acts like a rigid boundary and reflects this wave and sends it back towards the open end. At the end an antinode is formed and a node is formed at the wall. The distance between antinode and node is \[\frac{\lambda }{4}\]. Therefore, iff be the frequency of node emitted, then \[\lambda =\frac{v}{f}\,\Rightarrow \,\,\lambda =\,\frac{300}{600}\,=\frac{1}{2}\,m\] Maximum amplitude is obtained at distance -\[\frac{\lambda }{4}\,=\frac{1}{2}\times \,\frac{1}{4}\,=\frac{1}{8}\,m\]


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