CMC Medical CMC-Medical VELLORE Solved Paper-2015

  • question_answer
    The electric field associated with an electromagnetic wave propagating in a medium is given by \[E={{E}_{0}}\sin \,(4\pi \times {{10}^{6}}x-1.2\,\pi \times {{10}^{15}}t)\]where, \[x\]is in meter and \[t\] in second. The wavelength of wave is founed to be

    A)  \[5\times {{10}^{-7}}m\]                             

    B)  \[4\times {{10}^{-9}}m\]

    C)  \[6\times {{10}^{-7}}m\]                             

    D)  \[3\times {{10}^{-6}}m\]

    E)  None of these

    Correct Answer: A

    Solution :

                    Given wave is \[E={{E}_{0}}\sin \,(4\pi \times {{10}^{6}}x-1.2\pi \times {{10}^{15}}t)\] ?(i) But the standard wave equation is \[E={{E}_{0}}\sin \,(Kx-\omega t)\]                          ?(ii) Comparing Eqs.(i) and (ii), we get \[K=4\pi \times {{10}^{6}}\] \[\Rightarrow \]               \[\frac{2\pi }{\lambda }=4\pi \times {{10}^{6}}\] \[\Rightarrow \]               \[\lambda =\frac{2\pi }{4\pi \times {{10}^{6}}}=\frac{{{10}^{-6}}}{2}=5\times {{10}^{-7}}m\]


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