Question

A telescope of diameter $2m$ uses light of wavelength $5000\mathring{A}$ for cicnibng stars. The minimum angular separation between two stars whole image is just resalved by this telescope is

• A. $4\times {10}^{-5}rad$
• 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 $0.31\times {10}^{-6}rad$

Minimum angular seperation
$\Delta Q=\frac{1}{RP}=\frac{1.22\lambda }{d}$
$=\frac{1.22\times 5000\times {10}^{-10}}{2}=0.3\times {10}^{-6}rad$