An astronomical telescope has an angular magnification of magnitude 5 for distant object. The separation between the objective and the eyepiece is 36 cm and the final image is formed at infinity. The focal length `f_(0)` of the objective and the focal length `f_(0)` of the eyepiece areA. `f_(o) = 45 cm and f_(e) = -9cm`B. `f_(o) = -7.2 cm and f_(e) = 5 cm`C. `f_(o) = 50 cm and f_(e) = 10 cm`D. `f_(o) = 30 cm and f_(e) = 6 cm`

An astronomical telescope has an angular magnification of magnitude 5

1.	An astronomical telescope has an angular magnification of magnitude 5 for distant object. The separation between the objective and the eyepiece is 36 cm and the final image is formed at infinity. The focal length `f_(0)` of the objective and the focal length `f_(0)` of the eyepiece areA. `f_(o) = 45 cm and f_(e) = -9cm`B. `f_(o) = -7.2 cm and f_(e) = 5 cm`C. `f_(o) = 50 cm and f_(e) = 10 cm`D. `f_(o) = 30 cm and f_(e) = 6 cm`
Answer» Correct Answer - D In this case, `\|m\|=(f_(o))/(f_(e ))=5` …..(i) and length of telescope `= f_(o)+f_(e )=36` …..(ii) On solving Eqs. (i) and (ii), we get `f_(e )=6 cm, f_(o)=30 cm`

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