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JIPMER Jipmer Medical Solved Paper-2009

  • question_answer
    In a laboratory four convex lenses \[{{L}_{1,}}{{L}_{2,}}{{L}_{3}}\] and \[{{L}_{4}}\] of focal lengths 2, 4, 6 and 8 cm, respectively are available. Two of these lenses form a telescope of length 10 cm and magnifying power 4. The objective and eye lenses are respectively

    A)  \[{{L}_{2,}}{{L}_{3}}\]                                   

    B)  \[{{L}_{1,}}{{L}_{4}}\]                   

    C)  \[{{L}_{1,}}{{L}_{2}}\]                   

    D)         \[{{L}_{4,}}{{L}_{1}}\]

    Correct Answer: D

    Solution :

    Length of tube = 10 cm \[{{f}_{o}}+{{f}_{e}}=10\,cm\] Magnification \[m=\frac{{{f}_{o}}}{{{f}_{e}}}=4\] \[{{f}_{o}}=4{{f}_{e}}\] Putting in Eq. (i), \[5{{f}_{e}}=10\,cm\] or            \[{{f}_{e}}=2\,cm\] and        \[{{f}_{o}}=8\,cm\] \[{{f}_{o}}=8\,cm,\]\[{{f}_{e}}=2\,cm\] Hence, \[{{L}_{4}}\] and \[{{L}_{1}}\] will be used.


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