Question

A reflecting telescope has a large mirror for its objective with radius of curvature equal to 80 cm. The magnifying power of this telescope if eye piece used has a focal length of 1.6 cm is

• A. 100
• B. 50
• C. 25
• D. 5

Answer 1

Answer: (C)

25

Answer 2

: The focal length of objective mirror

$f_{o} = \frac{R}{2} = \frac{80}{2} = 40cm$

and focal length of eye piece,$= 1.6cm$

$\therefore$ Magnifying power, $m = \frac{f_{o}}{f_{e}} = \frac{40}{1.6} = 25$