In Fresnel’s biprism (μ=1.5) experiment the distance between source and biprism is 0.3 m  and that between biprism and screen is 0.7m and angle of prism is 1°. The fringe width with light of wavelength 6000 Å will be

β=(a+b)λ2a(μ−1)α where a = distance between source and biprism = 0.3 m b = distance between biprism and screen = 0.7 m. α = Angle of prism = 1°, μ = 1.5,  λ= 6000 × 10–10 m   Hence, β=(0.3+0.7)×6×10−72×0.3(1.5−1)×1∘×π180 =1.14×10−4m=0.0114cm