Q 12-10-120JEE MainJEE Main 2020 (9 Jan, Shift 1)Easy
The aperture diameter of a telescope is $5$ m. The separation between the moon and the earth is $4\times10^5$ km. With light of wavelength of $5500$ Å, the minimum separation between objects on the surface of moon, so that they are just resolved, is close to:
Answer: (A) $60$ m
Limit of resolution: $\theta = \dfrac{1.22\lambda}{D} = \dfrac{1.22\times5500\times10^{-10}}{5} = 1.34\times10^{-7}$ rad.
$$x = \theta\times d = 1.34\times10^{-7}\times4\times10^8 \approx 54\ \text{m}$$
The closest option is $60$ m.
Solution by Sreeraj P, M.Sc Physics