Young's Double Slit Experiment
and N-slit Diffraction

Variables you can adjust:

d - the distance between two adjacent slits.

λ - the wavelength of the incident light.

a - the width of the slits.

N - the number of slits.

Single Slit Effects

Note the irradiance minima when sin(α) = 0, where α = (ka/2) sin(θ).

Note the irradiance maxima where α = +/- 1.43π, +/- 2.459π, ...

Double Slit Effects

Note the irradiance minima when cos(δ) = 0, where δ = (kd/2) sin(θ).

Note the half-fringes or missing orders that occur when d/a = n, where n is an integer.

N Slit Effects

Note the irradiance minima when sin(N*δ) = 0, where δ = (kd/2) sin(θ).

Notice the N-2 subsidiary minima between the principle maxima.