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

  • question_answer
    If convex lens of focal length 80cm and a concave lens of focal length 50 cm are combined together, what will be their resulting power                                                             [AFMC 2002]

    A)            + 6.5 D                                    

    B)            ? 6.5 D

    C)            + 7.5 D                                    

    D)            ? 0.75 D

    Correct Answer: D

    Solution :

                       \[\frac{1}{F}=\frac{1}{{{f}_{1}}}+\frac{1}{{{f}_{2}}}\Rightarrow \frac{1}{F}=\frac{1}{+80}+\frac{1}{-50}\]            \[\Rightarrow \] \[F=-\frac{400}{3}\Rightarrow P=\frac{-\,3}{4}D\]


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