MGIMS WARDHA MGIMS WARDHA Solved Paper-2014

  • question_answer
    Light passes through two polaroids\[{{P}_{1}}\]and \[{{P}_{2}}\] with pass axis of \[{{P}_{2}}\]making an angle 6 with the pass axis of \[{{P}_{1}}\]. That value of 9 for which the intensity of emergent light is zero.

    A)  \[45{}^\circ \]                  

    B)  \[90{}^\circ \]

    C)  \[30{}^\circ \]                  

    D)  \[60{}^\circ \]

    Correct Answer: A

    Solution :

                    (i) The value of\[\theta \] is\[90{}^\circ \]for which the intensity of emergent light from\[{{P}_{2}}\]is zero as \[cos\text{ }90{}^\circ =0\] (ii) If\[{{I}_{0}}\]be the intensity of uhpolarised light on \[{{p}_{1}},\]then the intensity of light emerging from \[{{p}_{1}}\]will be \[\frac{{{I}_{0}}}{2}\]. The intensity of light after passing through second test polaroid\[{{p}_{2}}\]will be                 \[I=\frac{{{I}_{0}}}{2}{{\cos }^{2}}\theta {{\sin }^{2}}\theta \] So,          \[\frac{{{I}_{0}}}{8}=\frac{{{I}_{0}}}{8}{{\sin }^{2}}2\theta \]                 \[{{\sin }^{2}}2\theta =1\]                 \[\sin 2\theta =1\]                 \[2\theta =90{}^\circ \]                 \[\theta =45{}^\circ \]


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