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AMU Medical AMU Solved Paper-2001

  • question_answer
    A person who can see things most clearly at a distance of 10 cm requires spectacles to enable him to see clearly things at a distance of 30 cm. The focal length of the spectacles is

    A)  10 cm                                  

    B)  18 cm

    C)  30 cm                                  

    D)  15 cm

    Correct Answer: D

    Solution :

                     For viewing far objects, concave lenses are used and for concave lens                 u = wants to see = - 30                 v = can see = - 10 So from                \[\frac{1}{f}=\frac{1}{v}-\frac{1}{u}\] \[\Rightarrow \]               \[\frac{1}{f}=\frac{1}{-10}+\frac{1}{30}\]                 \[\frac{1}{f}=\frac{-3+1}{30}\]                 \[f=-15\,cm\]


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