Question

Why does the objective of an optical telescope have large focal length and large aperature?

Answer 1

Telescopes want to collect more light to show faint objects..So the objective lens or mirror is always larger.

Telescopes do 3 things

1 collect more light than your eye.

2 they resolve close objects.

3 they magnify. the functions 1 and 2 are depend upon the size of objective .

Hope that helps you!!!! ☺️☺️