JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer
    A wave travelling along positive \[x-axis\] is given by\[y=A\sin (\omega t-kx)\]. If it is reflected from a rigid boundary such that \[80%\] amplitude is reflected, then equation of reflected wave is

    A) \[y=A\sin (\omega t+0.8\,\,kx)\]

    B) \[y=-0.8\,\,A\sin (\omega t+kx)\]

    C)  \[y=A\sin (\omega t+kx)\]

    D)  \[y=0.8\,\,A\sin (\omega t+kx)\]

    Correct Answer: B

    Solution :

    On getting reflected from a rigid boundary the wave suffers. Hence, if\[{{y}_{incident}}=A\sin (\omega t-kx)\] Then,\[{{y}_{reflected}}=(0.8A)\sin \{\omega t-k(-x)+\pi \}\]                 \[=-0.8\,\,A\sin (\omega t+kx)\]an additional phase change of\[\pi \].


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