An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of

Options

A. small focal length and large diameter
B. large focal length and small diameter
C. large focal length and large diameter
D. small focal length and small diameter

Answer

C

Explanation

For telescope, angular magnification `=(f_(0))/(f_(e))`
Angular resolution `=(D)/(1.22lambda)` should be large.
So, objective lens should have large focal length `(f_(0))` and large diameter D for large angular magnification and high angular resolution.