Question

An opera glass `(`Galilean telescope ) measures `9cm` from the objective to the eyepiece. The focal length of the objective is `15 cm`. Its magnifying power is
A. `2.5`
B. `2//5`
C. `5//3`
D. `0.4`

Answer 1

Correct Answer - A
`f_(o)-f_(e)=9cm` and `f_(e)=f_(o)-9=15-9=6cm`
`impliesm=(f_(e))/(f_(e))=(15)/(6)=2.5`