Using the appropriate approximations:
dx/L = mλ
d = slit separation
x = fringe spacing
L = distance between slits and screen
m = some integer, used to determine the distance from the central bright fringe to another bright fringe
We don't really need a value for m because we're calculating the distance between any pair of consecutive fringes. Let's just set m = 1
Given values:
d = 1.0mm
L = 2.0m
λ = 480nm
Substitute the terms in the equation with our given values and solve for x:
1.0*10⁻³*x/2 = 480*10⁻9
x = 0.96mm
