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

  • question_answer
    The radius of the convex surface of plano-convex lens is 20 cm and the refractive index of the material of the lens is 1.5. The focal length of the lens is                                  [CPMT 2004]

    A)            30 cm                                      

    B)            50 cm

    C)            20 cm                                      

    D)            40 cm

    Correct Answer: D

    Solution :

               \[\frac{1}{F}=(1.5-1)\ \left( \frac{1}{20}-\frac{1}{\infty } \right)\]\[\Rightarrow F=40\,cm\].


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