Haryana PMT Haryana PMT Solved Paper-2005

  • question_answer
    A wave represented by the equation  \[\text{y=acos}\,\text{(kx- }\!\!\omega\!\!\text{ t)}\] is superimposed with another wave to form a stationary wave such that the point x = 0 is a node. The equation of the other wave is :

    A) \[a\sin \,(kx-\omega t)\]                             

    B) \[-a\cos (kx-\omega t)\]

    C) \[-a\cos (kx+\omega t)\]             

    D) \[-a\cos (kx+\omega t)\]

    Correct Answer: D

    Solution :

                    Since, the point \[x=0\] is a node and reflection is taking place from point \[x=0\] i.e,, reflection must be taking place from the fixed end. Hence,; the reflected ray must suffer an additional phase change of \[\pi \]. So,      if             \[{{y}_{incident}}=a\,\cos (kx-\omega t)\] \[\therefore \]  \[{{y}_{reflected}}=a\cos (-kx-\omega t+\pi )\]                 \[=-a\cos (\omega t+kx)\]


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