If prism angle α = 1°, µ = 1.54, distance between screen and prism (b) = 0.7 m, distance between prism and source a = 0.3m, λ = 180π nm then in Fresnal biprism find the value of β (fringe width)

10^-4 m

By using $\beta=\frac{(a+b) \lambda}{2 a(\mu-1) \alpha}=\frac{(0.3+0.7) \times 180 \pi \times 10^{-9}}{2 \times 0.3(1.54-1) \times\left(1 \times \frac{\pi}{180}\right)}=10^{-4}$ m