JCECE Engineering JCECE Engineering Solved Paper-2014

  • question_answer
    When the angle of incidence is \[{{60}^{o}}\] on the surface of a glass slab, it is found that the reflected ray is completely polarised. The velocity of light in glass is

    A) \[\sqrt{2}\times {{10}^{8}}m{{s}^{-1}}\]               

    B) \[\sqrt{3}\times {{10}^{8}}m{{s}^{-1}}\]

    C) \[2\times {{10}^{8}}m{{s}^{-1}}\]                             

    D) \[3\times {{10}^{8}}m{{s}^{-1}}\]

    Correct Answer: B

    Solution :

    Refractive index of glass                 \[{{\mu }_{g}}=\tan {{O}_{P}}\] where,\[{{O}_{P}}=\] polarising angle                 \[{{\mu }_{g}}=\tan {{60}^{o}}=\sqrt{3}\]                 \[{{\mu }_{g}}=\frac{c}{{{v}_{g}}}\]                 \[\frac{c}{{{v}_{g}}}=\sqrt{3}\]                 \[{{v}_{g}}=\frac{3\times {{10}^{8}}}{\sqrt{3}}=\sqrt{3}\times {{10}^{8}}\,\,m/s\]


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