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

  • question_answer
    A man who cannot see clearly beyond 5 m wants to see stars clearly. He should use a lens of focal length [MP PET/PMT 1988; Pb. PET 2003]

    A)            ? 100 m                                  

    B)            + 5 m

    C)            ? 5 m                                       

    D)            Very large 

    Correct Answer: C

    Solution :

                       For lens u = want?s to see =\[\infty \] v = can see = ? 5 m            \ From \[\frac{1}{f}=\frac{1}{v}-\frac{1}{u}\]\[\Rightarrow \frac{1}{f}=\frac{1}{-5}-\frac{1}{\infty }\]\[\Rightarrow f=-5\,m.\]


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