RAJASTHAN PMT Rajasthan - PMT Solved Paper-2009

  • question_answer
    A ray of light propagates from glass (refractive index = 3/2) to water (refractive index = 4/3). The value of the critical angle is

    A)  \[{{\sin }^{-1}}\left( \frac{1}{2} \right)\]                               

    B)  \[{{\sin }^{-1}}\left( \sqrt{\frac{8}{9}} \right)\]

    C)  \[{{\sin }^{-1}}\left( \frac{8}{9} \right)\]               

    D)         \[{{\sin }^{-1}}\left( \frac{5}{7} \right)\]

    Correct Answer: C

    Solution :

    Refractive index of glass with respect to water                 \[_{w}{{\mu }_{g}}=\frac{_{a}{{\mu }_{g}}}{_{a}{{\mu }_{w}}}=\frac{3/2}{4/3}=\frac{9}{8}\]                 \[_{w}{{\mu }_{g}}=\frac{1}{\sin C}\]                 \[\frac{9}{8}=\frac{1}{\sin C}\]         \[\sin C=\frac{8}{9}\]                           \[C={{\sin }^{-1}}\left( \frac{8}{9} \right)\]


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