CET Karnataka Medical CET - Karnataka Medical Solved Paper-2011

  • question_answer
    A prism having refractive index 1.414 and refracting angle \[30{}^\circ \] has one of the refracting surfaces silvered. A beam of light incident on the other refracting surface will retrace its path, if the angle of incidence is

    A)  \[0{}^\circ \]

    B)  \[30{}^\circ \]

    C)  \[60{}^\circ \]

    D)  \[45{}^\circ \]

    Correct Answer: D

    Solution :

    At second surface, there is no refraction so \[{{r}_{2}}=0\] \[\therefore \] \[{{r}_{1}}=A={{30}^{o}}\] From Snells law \[n=\frac{\sin {{i}_{1}}}{\sin \,{{r}_{1}}}\] \[n=\frac{\sin {{i}_{1}}}{\sin {{30}^{o}}}\] \[\sin {{i}_{1}}=\sqrt{2}\times \frac{1}{2}=\frac{1}{\sqrt{2}}\] \[\sin {{i}_{1}}=\frac{1}{\sqrt{2}}\] \[{{i}_{1}}={{45}^{o}}\]


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