Skip to content

JEE MAIN 2026 · Optics

JEE Main 2026 Session 2 Question Paper: 8 Apr, Shift 2 (B.E./B.Tech), question 47

Updated
Numerical answer+4 / -1Answer matches NTA’s final key

Some distant star is to be observed by some telescope of diameter of objective lens aa, at an angular resolution of 3.0×10−73.0 \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)

Your answer

Solution

Solution

The Rayleigh limit for a circular aperture is θ=1.22λa\theta = \dfrac{1.22\lambda}{a}, so

a=1.22×500×10−93.0×10−7=2.033 m≈203 cm.a = \frac{1.22 \times 500 \times 10^{-9}}{3.0 \times 10^{-7}} = 2.033 \text{ m} \approx 203 \text{ cm}.

Answer: 203 cm.

Answer checked against the official answer key. The solution is our own working.

Keep going

Some distant star is to be observed by… | SchoolToCareer