• # question_answer A telescope has an objective lens of 10 diameter and is situated at a distance of 1 km from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is $5000\,\overset{o}{\mathop{\text{A}}}\,$, is of the order of A)  0.5m                           B)  5m             C)  6mm                           D)  7cm

If $x$ is the distance between two objects and d is the distance between the telescope and the two objects, then$d\theta =\frac{x}{d}=\frac{1.22\lambda }{D}$ or $x=\frac{1.22\lambda d}{D}=\frac{1.22\times 5000\times {{10}^{-10}}\times 1000}{0.10}m$ $=6.0\times {{10}^{-3}}\,\approx \,\,\text{6}\,\,\text{mm}$