69. A telescope has an objective lens of 10 cm diameter and is situated at a distance of one kilometer from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 Å, is of the order of ?

69. A telescope has an objective lens of 10 cm diameter and is situated at a distance of one kilometer from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 Å, is of the order of ?

(a) 5 cm

(b) 0.5 m

(c) 5 m

(d) 5 mm

Answer :  (d) 5 mm

\(\delta_{\text{min}} \cdot D = d \; \; (\text{Sector Formula})\)

\(5 \times 10^{-6} \cdot 10^{3} = d\)

\(d = 5 \times 10^{-3} \; m\)