The path difference when transparent sheet is introduced Δx = (µ – 1)t If the central maxima occupies position of nth fringe, then (µ – 1)t = n λ = d sin θ ⇒ sin θ = d(μ−1)t = 3×10−7(1.17−1)×1.5×10−7 = 0.085 Therefore, angular position of central maxima θ = sin−1 (0.085) = 4.88° = 4.9 For small angles, sin θ = θ = tan θ ⇒ tan θ = Dy ∴ Dy = d(μ−1)t ⇒ y = dD(μ−1)t
