Physics · Wave Optics

JEE Main 2026 — 8 April, Evening Shift — Question 18

Some distant star is to be observed by a telescope of diameter of objective lens a, at an angular resolution of $3.0\times10^{-7}$ radian. If the wavelength of light from the star reaching the telescope is $500~\mathrm{nm}$ , the minimum diameter of the objective lens of the telescope is cm. (Nearest integer)

Answer: 203

Numerical answer — enter this value.

Step-by-step solution

Angular resolution $\theta = 1.22\lambda/D$ ⇒ $D = 1.22\lambda/\theta = 1.22\times500\times10^{-9} / (3.0\times10^{-7}) = 2.0333$ m = 203.33 cm ≈ 203 cm.

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 8 April, Evening Shift
Subject: Physics
Chapter: Wave Optics
Topic: Diffraction of Light Waves