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
Concept. Angular resolution of a circular objective: $\theta=\dfrac{1.22\lambda}{D}$.
Step 1. Diameter. $D=\dfrac{1.22\times500\times10^{-9}}{3\times10^{-7}}=2.03$ m.
Answer. $203$ cm.
Solution by Sreeraj P, M.Sc Physics
