Question

A telescope of diameter 2m uses light of wavelength $5000\dot{A}$ for viewing stars. The minimum angular separation between two stars whose image is just resolved by this telescope is

• A. $4\times {10}^{4}rad$
• B. $0.25\times {10}^{-6}rad$
• C. $0.31\times {10}^{-6}rad$
• D. $5.0\times {10}^{-3}rad$

Answer 1

The correct option is C $0.31\times {10}^{-6}rad$

Resolving limit
${\theta }_m=\frac{1.22\lambda }{a}$
$=\frac{1.22\times 5000\times {10}^{-10}}{2}$
=$0.31\times {10}^{-6}rad$