Draw a labelled ray diagram showing the formation of the image at infinity by an astronomical telescope.

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

Draw a labelled diagram to show the structure of earth.

Draw a neat labelled diagram showing steps of PCR.