Question

Two beams of Light of intensity I₁ and I₂ interfere to give an interference pattern. If the ratio of maximum intensity to that of minimum intensity is (16 / 4) then (I₁ / I₂) = ________. 

(A) 1 : 9 (B) 1 : 4 (C) 4 : 1 (D) 9 : 1

Answer 1

The correct option is (D) 9 : 1.

Explanation:

Intensity ∝ (amplitude)²  i.e. I ∝ A²

When two beams of amplitude A₁ & A₂ superimpose, maxima and minima of resultant is (A₁ + A₂) and (A₁ – A₂) if the maximum and minimum intensities are I_max and I_min then

Hence (I₁ / I₂) = (A₁² / A₂²) = [(3A₂)² / (A₂²)] = (9 / 1).