Physics · Geometrical Optics
JEE Main 2026 — 4 April, Morning Shift — Question 17
A telescope with objective diameter R is used to observe a distant star emitting light of wavelength 500 nm, at a resolution of 5×10⁻⁷ radian. The value of R is ______ cm.
- Option A:
61
- Option B:Correct
122
- Option C:
244
- Option D:
305
Answer: B
Step-by-step solution
Resolution θ = 1.22λ/R ⇒ R = 1.22λ/θ = 1.22×500×10⁻⁹ / (5×10⁻⁷) = 1.22×1 = 1.22 m = 122 cm
Answer key and solution verified before publishing.
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- Exam
- JEE Main 2026
- Subject
- Physics
- Chapter
- Geometrical Optics
- Topic
- Optical Instruments