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

  • question_answer
    A point source of light is placed 4 m below the surface of water of refractive index 5 / 3. The minimum diameter of a disc which should be placed over the source on the surface of water to cut?off all light coming out of water is [CBSE PMT 1994; JIPMER 2001, 02]

    A)            2 m                                           

    B)            6 m

    C)            4 m                                           

    D)            3 m

    Correct Answer: B

    Solution :

                       Here \[\sin i=\frac{1}{\mu }=\frac{3}{5}\] and hence \[\tan i=\frac{3}{4}=\frac{r}{4}\] This gives \[r=3\,m\], hence diameter = \[6m\]


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