Question

A Galileo telescope has an objective of focal length `100cm` and magnifying power 50. The distance between the two lenses in normal adjustment will be
A. `150 cm`
B. `100 cm`
C. `98 cm`
D. `200 cm`

Answer 1

Correct Answer - A
In normal adjustment
`m=-(f_(0))/(f_(e))`
so `50=-(100)/(f_(e))` `rArr` `f_(e)=-2 cm`
(`therefore` eyepiece is concave lens)
and `L=f_(0)+f_(e)=100-2=98 cm`