BCECE Engineering BCECE Engineering Solved Paper-2004

  • question_answer
    If focal lengths of the objective and the eye                 piece of a telescope be\[{{f}_{0}}\]and\[{{f}_{e}}\] respectively, then its magnification is :

    A)  \[\frac{1}{2}({{f}_{0}}+{{f}_{e}})\]          

    B)        \[{{f}_{0}}/{{f}_{e}}\]

    C)        \[({{f}_{0}}+{{f}_{e}})\]                

    D)         \[{{f}_{0}}\times {{f}_{e}}\]

    Correct Answer: B

    Solution :

    Magnification of telescope is given by \[M=\frac{{{f}_{o}}}{{{u}_{e}}}\] where \[{{u}_{e}}\]is first image distance from eyepiece. For relaxed eye, intermediate image should lie at first focus of eyepiece or \[{{u}_{e}}={{f}_{e}}\] \[\therefore \]  \[M=\frac{{{f}_{o}}}{{{f}_{e}}}\]


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