BCECE Medical BCECE Medical Solved Papers-2007

  • question_answer
    Sound waves of \[f=600\] 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)

    A)  \[\frac{7}{8}\]m            

    B)  \[\frac{3}{8}\]m

    C)  \[\frac{1}{8}\]m            

    D)  \[\frac{1}{4}\]m

    Correct Answer: C

    Solution :

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


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