RAY OPTICS AND OPTICAL INSTRUMENTS — Physics STD 12 Science — Question

→The main considerations with an astronomical telescope are its light gathering power and its resolution (or resolving power).
→In objective lens light gathering power depends on the area of the objective.
→With larger diameters, fainter objects can be observed. The resolving power or the ability to observe two objects distinctly also depends on the diameter of the objective. So the desirable aim in optical telescope is to make them with objective of large diameter.
→The largest lens objective in use has a diameter of 40 inch (~ 1.02 m). It is at the Yerks observatory in Wisconsin, USA.