Question

A pair of slits in a double slit experiment are illuminated with monochromatic light of wavelength 480 nm. The slits are separated by 1.0mm. What is the separation of the fringes when observed at a distance of 2.0 m from the slits?
Please show work.

Answer 1

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