2. Questions Bank
  3. JEE Main & Advanced
  4. Physics
  5. Ray Optics

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

  • question_answer
    The focal length of the objective of a terrestrial telescope is 80 cm and it is adjusted for parallel rays, then its magnifying power is 20. If the focal length of erecting lens is 20 cm, then full length of telescope will be  

    A)            84 cm                                      

    B)    100 cm  

    C)            124 cm                                    

    D)    164 cm  

    Correct Answer: D

    Solution :

                       \[m=\frac{{{f}_{o}}}{{{f}_{e}}}=\frac{100}{2}=50\]cm                    Hence length of terrestrial telescope            \[={{f}_{o}}+{{f}_{e}}+4f\]\[=80+4+4\times 20=164\ cm\]


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