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JEE Main & Advanced Physics Ray Optics Question Bank Refraction at Curved Surface

  • question_answer
    A plano-convex lens is made of refractive index of 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is                                                   [Pb. PET 2000]

    A)            400 cm                                    

    B)            200 cm

    C)            100 cm                                    

    D)            50 cm

    Correct Answer: C

    Solution :

                       \[\frac{1}{f}=(\mu -1)\ \left( \frac{1}{{{R}_{1}}}-\frac{1}{{{R}_{2}}} \right)\]            \[\frac{1}{f}=(1.6-1)\ \left( \frac{1}{60}-\frac{1}{\infty } \right)\]\[=\frac{1}{100}\]\[\Rightarrow f=100\,cm\]


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