In a YDSE, films of thickness tₐ and tᵦ and refractive indices μₐ and μᵦ are placed before slits A and B. If μₐtₐ=μᵦtᵦ, how does the central maximum shift?
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Question

In a YDSE, films of thickness tₐ and tᵦ and refractive indices μₐ and μᵦ are placed before slits A and B. If μₐtₐ=μᵦtᵦ, how does the central maximum shift?

G1 Physics · Accepted Answer

The extra optical paths are (μₐ−1)tₐ and (μᵦ−1)tᵦ. Since μₐtₐ=μᵦtᵦ, their difference is tᵦ−tₐ. Therefore the central fringe shifts toward A when tᵦ>tₐ and toward B when tᵦ<tₐ. Option D.