Home/
Competitive Exams/
JEE Main & Advanced/
Physics/
Electromagnetic Waves and Wave Optics/
Question 20254
JEE Physics · Hard

Electromagnetic Waves and Wave Optics: Newton's Rings — Radius Formula MCQ

Solve this quality-checked JEE multiple-choice question, then review the correct answer and explanation.

Timer-based practiceDetailed answer reviewMobile-friendly flow
Newton's Rings — Radius FormulaHardQuestion 20254

Question

Radius of nth bright Newton's ring (radius of curvature R, wavelength λ, thin air film) in reflected light is:
  1. A
    √(nλR)
  2. B
    √((n+½)λR)
    Correct
  3. C
    √(nλ/R)
  4. D
    nλR

Correct answer

√((n+½)λR)

Explanation

For bright rings in reflected light: 2t = (n+½)λ (accounting for the π phase change). For a plano-convex lens: t = r²/(2R). So r² = (n+½)λR → r_n = √((n+½)λR).

Review Electromagnetic Waves and Wave Optics notesStart timed chapter practice