CET Karnataka Medical CET - Karnataka Medical Solved Paper-2007

  • question_answer
    When the angle of incidence is \[60{}^\circ \] 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,\[{{\mu }_{g}}=\tan {{\theta }_{P}}\]where \[{{\theta }_{P}}=\] polarising angle \[\Rightarrow \] \[{{\mu }_{g}}=\tan {{60}^{o}}=\sqrt{3}\] Now,       \[{{\mu }_{g}}=\frac{c}{{{v}_{g}}}\] \[\therefore \] \[\frac{c}{{{v}_{g}}}=\sqrt{3}\] \[\Rightarrow \] \[{{v}_{g}}=\frac{3\times {{10}^{8}}}{\sqrt{3}}\] \[=\sqrt{3}\times {{10}^{8}}m/s\]


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