Question

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

• A. Large focal length and large diameter
• B. Small focal length and large diameter
• C. Small focal length and small diameter
• D. Large focal length and small diameter

Answer 1

Answer: (A)

Large focal length and large diameter

Angular magnification = - $\frac{f_o}{f_e}$

Resolution $\propto D$

Hence for an astronomical refracting telescope having larger focal length and larger diameter for large angular magnification and high resolution.