AMU Medical AMU Solved Paper-2013

  • question_answer
    The magnetic component of a polarised wave of light is \[{{B}_{x}}=(4.0\times {{10}^{-4}}T)\sin [1.57\times {{10}^{7}}{{m}^{-1}})y+\omega t)\] The intensity of light is

    A)  \[1.9\,kW/{{m}^{2}}\]                  

    B)  \[3.8\,kW/{{m}^{2}}\]

    C)  \[5.7\,kW/{{m}^{2}}\]                  

    D)  \[7.6\,kW/{{m}^{2}}\]

    Correct Answer: A

    Solution :

                     Given that \[Bn=(4.0\times {{10}^{-6}}T)\sin \,[(1.57\times {{10}^{7}}{{m}^{-1}})y+\omega \,t]\] This equation comparing with                 \[B={{B}_{0}}\sin \left[ \frac{2\pi V}{\lambda }+\omega \,t \right]\], we get                 \[{{B}_{o}}=4\times {{10}^{-6}}T\] Now, from          \[l=\frac{CB_{0}^{2}}{2{{\mu }_{0}}}\] but         \[{{C}^{2}}=\frac{1}{{{\varepsilon }_{0}}{{H}_{0}}}\] \[\therefore \]  \[l=\frac{1}{2}{{C}^{3}}{{\varepsilon }_{0}}B_{0}^{2}\]                 \[l=1.9\,kW/{{m}^{2}}\]


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