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

  • question_answer
    A convex lens of focal length 84 cm is in contact with a concave lens of focal length 12 cm. The power of combination (in diopters) is                                                                    [MP PET 1991]

    A) 25/24                                       

    B) 25/18

    C) - 50/7                                     

    D) + 50/7

    Correct Answer: B

    Solution :

    Focal length of the combination                    \[\frac{1}{F}=\frac{1}{{{f}_{1}}}+\frac{1}{{{f}_{2}}}\]\[=\frac{1}{(+84)}+\frac{1}{(-12)}\]\[\Rightarrow F=-14\ cm\]            \[\therefore P=\frac{100}{F}=\frac{100}{-14}=-\frac{50}{7}D\]


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