Q. The focal lengths of the objective and eye lenses of a telescope are respectively $200\ cm$ and $5\ cm$. The minimum magnifying power of the telescope will be
A) $- 40$
B) $- 48$
C) $- 60$
D) $- 100$
Explanation
(b) Magnifying power of astronomical telescope
$m = - \frac{f_{o}}{f_{e}}\left( 1 + \frac{f_{e}}{D} \right) = - \frac{200}{5}\left( 1 + \frac{5}{25} \right) = - 48$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.