# The objective of a telescope has a diameter 5 cm. What is the angular seperation in radius of two starts which can be resolved by the telescope when light of $3000 A^{\circ}$ is used.

$(a)\;7.32 \times 10^{-6} \\ (b)\;6.02 \times 10^{-6} \\ (c)\;7.12 \times 10^{-6} \\ (d)\;5.12 \times 10^{-6}$

Resolving power $= \large\frac{1.22 \lambda}{d}$
$\qquad= \large\frac{1.22 \times 3000 \times 10^{-10}}{5 \times 10^{-2}}$
$\qquad= 7.32 \times 10^{-6}\;radius$
Hence a is the correct answer.