JCECE Engineering JCECE Engineering Solved Paper-2015

  • question_answer
    A Galilean telescope has an objective of focal length \[200\,\,cm\] and magnifying power\[100\]. What is the distance between the two lenses in normal?

    A) \[98\,\,cm\]                      

    B) \[198\,\,cm\]

    C) \[298\,\,cm\]                    

    D) \[3\,\,m\]

    Correct Answer: B

    Solution :

    In Galilean telescope, a convergent lens is used as the objective and a divergent lens as the eyepiece. Magnifying power and length of telescope are written as                 \[M=\frac{{{f}_{o}}}{{{u}_{e}}}\]and\[L={{f}_{o}}-{{u}_{e}}\] In normal adjustment,                 \[{{u}_{e}}={{f}_{e}}\] So,          \[{{M}_{\infty }}=\frac{{{f}_{o}}}{f}=100\] or            \[{{f}_{e}}=\frac{{{f}_{o}}}{100}=\frac{200}{100}=2\,\,cm\] and        \[{{L}_{\infty }}={{f}_{o}}-{{f}_{e}}=200-2=198\,\,cm\]


You need to login to perform this action.
You will be redirected in 3 sec spinner