Q. A telescope of diameter $2m$ uses light of wavelength $5000\ \mathring{\mathrm{A}}$ 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) $5.0 \times 10^{- 3}\ rad$
Explanation
(c) Minimum angular separation $\mathrm{\Delta}\theta = \frac{1}{R.P.} = \frac{1.22\ \lambda}{d}$
$= \frac{1.22 \times 5000 \times 10^{- 10}}{2} = 0.3 \times 10^{- 6}rad$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.