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

  • question_answer
    A telescope has an objective lens of focal length 200 cm and an eye piece with focal length 2 cm. If this telescope is used to see a 50 meter  tall building at a distance of 2 km, what is the height of the image of the building formed by the objective lens                                                              [AIIMS 2005]

    A)            5 cm                                         

    B)            10 cm

    C)            1 cm                                         

    D)            2 cm

    Correct Answer: A

    Solution :

                       Magnification of objective lens \[m=\frac{I}{O}=\frac{{{v}_{0}}}{{{u}_{0}}}=\frac{{{f}_{0}}}{{{u}_{0}}}\] Þ \[\frac{I}{50}=\frac{200\times {{10}^{-2}}}{2\times {{10}^{3}}}\]  Þ I = 5 ´ 10?2 m = 5 cm.


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