JEE Main & Advanced JEE Main Paper (Held on 10-4-2019 Morning)

  • question_answer
    A ray of light AO in vacuum is incident on a glass slab at angle \[60{}^\circ \] and refracted at angle \[30{}^\circ \] along OB as shown in the figure. The optical path length of light ray from A to B is: [JEE Main 10-4-2019 Morning]

    A) \[2a+2b\]

    B) \[2a+\frac{2b}{3}\]

    C) \[\frac{2\sqrt{3}}{a}+2b\]                

    D) \[2a+\frac{2b}{\sqrt{3}}\]

    Correct Answer: A

    Solution :

                From Snell's law \[1.sin60{}^\circ =\mu sin30{}^\circ \]             \[\Rightarrow \mu =\sqrt{3}\] Optical path\[=AO+\mu (OB)\] \[=\frac{a}{\cos {{60}^{o}}}+\sqrt{3}\frac{b}{\cos {{30}^{o}}}\]\[=2a+2b\]

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