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

  • question_answer
    The focal lengths of the lenses of an astronomical telescope are 50 cm and 5 cm. The length of the telescope when the image is formed at the least distance of distinct vision is [EAMCET (Engg.) 2000]

    A)            \[45\,cm\]                             

    B)            \[55\,cm\]

    C)            \[\frac{275}{6}\,cm\]        

    D)            \[\frac{325}{6}\,cm\]

    Correct Answer: D

    Solution :

                       Length of the telescope when final image is formed at least distance of distinct vision is            \[L={{f}_{o}}+{{u}_{e}}={{f}_{o}}+\frac{{{f}_{e}}D}{{{f}_{e}}+D}\]\[=50+\frac{5\times 25}{5+25}=\frac{325}{6}cm\]


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