Question

A ray of light of intensity I is incident on a parallel glass slab at point A as shown in diagram. It undergoes partial reflection and refraction. At each reflection, 25% of incident energy is reflected. The rays AB and A'B' undergo interference. The ratio of Imax and Imin is: 

• A. \(49:1\)
• B. \(7:1\)
• C. \(4:1\)
• D. 8:1

Hint:

For two-beam interference: Imₐₓ,mᵢₙ=(√(I₁)±√(I₂))² Always calculate intensities after each reflection/transmission.

Answer 1

The Correct Option is A

Step 1: Reflection coefficient: R=0.25, T=0.75
Step 2: Intensities of the two interfering rays: I₁ = 0.25I I₂ = (0.75)²(0.25)I
Step 3: Using interference formula: fracImaxImin =(frac√(I₁)+√(I₂)√(I₁)-√(I₂))²
Step 4: Substituting values gives: fracImaxImin=49:1