Question

Two convex lenses, of equal focal length but of aperture A1 and A2 (A1> A2) are used as the objective lenses in two astronomical telescopes have indentical eye-piece
Compare the ratio of their
I) Resolving Power
II) Normal magnifying power
III) Intensity of the image formed by them
Which of the telescopes should be preferred? Why?

Answer 1

Resolving power = 1.22 * (wavelength/ diameter)
so telescope has higher aperture will have less resolving power
So resolving power of second telescope A is high.

Focal length is same so magnification will be same.
Both has same magnification.

Intensity is proportional to square of diameter so A has higher aperture so intensity of image formd by A1 is considered.