Question

A telescope is made of a glass of focal length 20cm and eye-piece of
focal length 5cm both converging lenses. Find the magnifying power
(i) when eye is focused to receive parallel rays, and (ii) when the eye
sees the image situated at near point which is 25cm.​

Answer 1

Answer:

i)-4.8

ii)4

Explanation:

Magnifying power in near point adjustment for telescope is given by Fo/Fe=20/5=4

Magnifying power for normal adjustment is given by -(Fo/Fe)(1+Fe/D)=-4(1+1/5) =-24/5=-4.8