JEE Main & Advanced JEE Main Paper (Held On 12 May 2012)

  • question_answer
    A wave represented by the equation \[{{y}_{1}}=a\cos (kx-\omega t)\]is superimposed with another wave to form a stationary wave such that the point x ? 0 is node. The equation for the other wave is   JEE Main Online Paper (Held On 12 May 2012)

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

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

    C)                        \[a\cos \left( kx+\omega t+\frac{\pi }{2} \right)\]            

    D)                        \[a\cos \left( kx-\omega t+\frac{\pi }{2} \right)\]

    Correct Answer: B

    Solution :

                    Since the point x=0 is a node and reflection is taking place from point x = 0. This means that reflection must be taking place from the fixed end and hence the reflected ray must suffer an additional phase change of \[\pi \]or a path change of \[\frac{\lambda }{2}.\] So, if\[{{y}_{incident}}=a\cos (kx-\omega t)\] \[\Rightarrow \]\[{{y}_{incident}}=a\cos (-kx-\omega t+\pi )\] \[=-a\cos (\omega t+kx)\] Hence equation for the other wave \[y=a\cos (kx+\omega t+\pi )\]


You need to login to perform this action.
You will be redirected in 3 sec spinner