Question

Why does the objective of an optical telescope have large focal length and large
aperture? Also explain why does a reflector give better image of a small portion of the
celestial body?

Answer 1

Because of larger concave lens are placed in the telescope. So we can say that it has larger image

Answer 2

Telescopes have larger aperture for a reason and that is they create more area for light collection which provides a better distinguishing properties of minute details.

Larger focal length is good to made easily as it provides them with a bigger scope to lessen fabrication while permitting greater magnified resolution.

The reflector is the ones which use a mirror for gathering light and then focusing them in order to that the shape of the reflector which is parabolic facilitates the light rays coming parallel from celestial bodies be focused onto a single point.