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

  • question_answer
    A plano convex lens \[(f=20cm)\]is silvered at plane surface. Now f will be           [BHU 1995; DPMT 2001; MP PMT 2005]

    A)            20 cm                                      

    B)            40 cm

    C)            30 cm                                      

    D)            10 cm

    Correct Answer: D

    Solution :

               \[\frac{1}{F}=\frac{2}{{{f}_{l}}}+\frac{1}{{{f}_{m}}}\]\[\Rightarrow \]\[\frac{1}{F}=\frac{2}{20}+\frac{1}{\infty }\Rightarrow F=10\]\[cm\]


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