Question

(a) (i) Draw a labelled ray diagram to show the formation of image in an astronomical telescope for a distant object. 

(ii) Write three distinct advantages of a reflecting type telescope over a refracting type telescope. 

(b) A convex lens of focal length 10cm is placed coaxially 5cm away form a concave lens of focal length 10cm. If an object is placed 30cm in front of the convex lens, find the position of the final image formed by the combined system.

Answer 1

(ii) Advantages of Reflecting Telescope over Refracting Telescope: 

(a) Less chromatic aberration 

(b) Less spherical aberration 

(c) High resolving power 

(d) High intense image

(b) The position of image formed by convex lens is

That is final image is formed at infinity.