Question

A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope since : 

(1) a large aperture contributes to the quality and visibility of the images. 

(2) a large area of the objective ensures better light gathering power. 

(3) a large aperture provides a better resolution. 

(4) all of the above.

Answer 1

Option : (4). All of the above.

MP = \(\frac{f_0}{f_e}\)

R.P. = \(\frac{a}{1.22λ}\)

Large aperture(a) of the objective lens provides better resolution 

∴ Good quality of image is formed and also it gathers more light.