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JEE Main & Advanced Physics Ray Optics Question Bank Microscope and Telescope

  • question_answer
    In Gallilean telescope, if the powers of an objective and eye lens are respectively +1.25 D and ? 20 D, then for relaxed vision, the length and magnification will be 

    A)            21.25 cm and 16                  

    B)            75 cm and 20  

    C)            75 cm and 16                        

    D)            8.5 cm and 21.25  

    Correct Answer: C

    Solution :

                       \[{{f}_{o}}=\frac{1}{1.25}=0.8\,m\] and \[{{f}_{e}}=\frac{1}{-20}=-\,0.05\,m\] \ \[|{{L}_{\infty }}|\,=\,|{{f}_{o}}|\,-\,|{{f}_{e}}|\,=0.8-0.05=0.75\,m=75\,cm\] and \[|{{m}_{\infty }}|\,=\frac{{{f}_{o}}}{{{f}_{e}}}=\frac{0.8}{0.05}=16\]


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