JEE Main & Advanced Physics Ray Optics Question Bank Total Internal Reflection

  • question_answer
    Glass has refractive index m with respect to air and the critical angle for a ray of light going from glass to air is q. If a ray of light is incident from air on the glass with angle of incidence q, the corresponding angle of refraction is [MP PMT 2004]

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

    B)            \[{{90}^{o}}\]

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

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

    Correct Answer: C

    Solution :

                       \[_{a}{{\mu }_{g}}=\frac{1}{\sin \theta }\]\[\Rightarrow \mu =\frac{1}{\sin \theta }\]                     .....(i) Now from Snell's law  \[\mu =\frac{\sin i}{\sin r}\]\[=\frac{\sin \theta }{\sin r}\] \[\Rightarrow \sin r=\frac{\sin \theta }{\mu }\]                                                     .....(ii) From equation (i) and (ii) \[\sin r=\frac{1}{{{\mu }^{2}}}\]\[\Rightarrow r={{\sin }^{-1}}\left( \frac{1}{{{\mu }^{2}}} \right)\]


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