Q 12-10-028JEE MainJEE Main 2026 (8 Apr, Shift 2)Medium
Some distant star is to be observed by some telescope of diameter of objective lens $a$, at an angular resolution of $3.0 \times 10^{-7}$ radian. If the wavelength of light from the star reaching the telescope is $500$ nm, the minimum diameter of the objective lens of the telescope is ______ cm. (nearest integer)
Numerical value type. Enter your answer.
Answer: 203
The limit of resolution of a telescope is $\theta = \dfrac{1.22\lambda}{a}$.
$$a = \frac{1.22\lambda}{\theta} = \frac{1.22 \times 500 \times 10^{-9}}{3.0 \times 10^{-7}} = 2.033\ \text{m} \approx 203\ \text{cm}$$
Solution by Sreeraj P, M.Sc Physics