A Galilean telescope is 27 cm long when focussed to form an image at infinity. If the objective has a focal length of 30 cm, what is the focal length of the eyepiece?
Given data
Focal length of the objective lens of the telescope, fo = 30 cm
Length of the tube, L = 27 cm
The image will be formed at infinity
We know that ,
A Galilean telescope, concave lens as eyepiece lens –
So,