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?

Explanation

Given, `f_(o)=+30cm`
Length of telescope is given,27 cm
Therefore, `u_(e)=+3 cm`
For the final image at infinity, the intermediate image should lie at first focus of eyepiece of the galilean telescope.
`therefore f_(e)=-3cm`