A small telescope has an objective lens of focal length 140 cm and eyepiece of focal length 5.0 cm. What is the magnifying power of the telescope for viewing distant objects when (a) the telescope is in normal adjustment and (b) the final image is formed at least distance of distinct vision ?

Explanation

Data supplied,
`f_(0) = 140 cm, " " f_(e) = 5.0` cm
a. M = -`(f_(0))/(f_(e)) = (-140.0)/(5) = - 28`
b. ` m = - (f_(0))/(f_(e)) ( 1 + (f_(e))/(D) ) = - (140)/(5) ( 1 + (5)/(25) ) = - 33.6`