Question

A small telescope has an objective lens of focal length 140 cm and an eyepiece of focal length 5.0 cm. What is the magnifying power of the telescope for viewing distant objects when b) the final image is formed at the least distance of distinct vision (25 cm) ?

Answer 1

Here, `f_(0)=140cm, f_(e)=5.0cm`
Magnifying power = ?
b) When final image is at the least distance of distinct vision,
Magnifying power
`=(-f_(0))/(f_(e))(1+(f_(e))/(d))=(-140)/(5)(1+(5)/(25))=-33.6`