Question

(a) Draw a ray diagram depicting the formation of the image by an astronomical telescope in normal adjustment.
(b) You are given the following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct an astronomical telescope ? Give reason.

Answer 1

(a)
(b) An astronomical telescope should have an objective of large aperture and longer focal length while an eyepiece of small aperture and small focal length. Therefore, we will use $L_1$ as an objective and $L_3$ as an eyepiece.