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JEE Main & Advanced Physics Question Bank Human Eye and Lens Camera

  • question_answer
    A person's near point is 50 cm and his far point is 3 m. Power of the lenses he requires for (i)       reading and (ii)      for seeing distant stars are                        [MP PMT 1994]

    A)            ? 2 D and 0.33 D                  

    B)            2 D and ? 0.33 D

    C)            ? 2 D and 3 D                        

    D)            2 D and ? 3 D

    Correct Answer: B

    Solution :

                       For correcting the near point, required focal length                    \[f=\frac{50\times 25}{(50-25)}=50\,cm\]                    So power \[P=\frac{100}{50}=+\,2\,D\]                    For correcting the far point, required focal length                    \[f=-\,(defected\ far\ point)=-\,3\,m\]            \[\therefore P=-\frac{1}{3}D=-\,0.33\,D\]


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