Question

Two convex lenses of same focal length but of aperture $A1$ and $A2(A2<A1)$ , are used as the objective lenses in two astronomical telescope having identical eyepieces, what is the ratio of there resolving power? Which telescope will you prefer and why? Give reason.

Answer 1

Resolving power = $\frac{a}{1.22\lambda }$

$\frac{R.P_1}{R.P_2}=\frac{A_1}{A_2}$

The telescope with the objective of aperture A1 should be preferred for viewing as this would:(i) give a better resolution(ii) have a higher light gathering power of telescope.