In a YDSE experiment, a slab whose refractive index μ can be varied is placed in front of one slit. Which graph best represents the resultant intensity at the midpoint of the screen versus μ (μ≥1)? Assume equal slit widths and no absorption.
Options

Question

In a YDSE experiment, a slab whose refractive index μ can be varied is placed in front of one slit. Which graph best represents the resultant intensity at the midpoint of the screen versus μ (μ≥1)? Assume equal slit widths and no absorption.

Options

G1 Physics · Accepted Answer

At the midpoint the geometrical path difference is zero. A slab before one slit adds optical path Δ=(μ-1)t, so I=4Iₛcos²[π(μ-1)t/λ]. Thus intensity varies periodically as a cos² function of μ and is maximum at μ=1. The graph with this behavior is Image 3. Option C.