An astronomical refracting telescope will have large angular magnification and high angular resolution…

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

(a) large focal length and large diameter

(b) small focal length and small diameter

(c) large focal length and small diameter

(d) small focal length and large diameter

Ans: (a)

Sol: Angular magnification $ \displaystyle m = \frac{f_o}{f_e}$

Angular resolution $ \displaystyle \theta = \frac{D}{1.22 \lambda}$