2D Wavefront Pattern
Circular wavelets from each slit superpose — bright regions = constructive interference
Intensity vs sin θ
Dashed line = single-slit diffraction envelope | Filled = multi-slit interference
Parameters
Number of slits N2
18
Slit separation d4.0 μm
1 μm12 μm
Wavelength λ550 nm
380 nm (violet)700 nm (red)
Slit width a1.0 μm
0.2 μm (wide fringes)4 μm (narrow)
Animation speed100%
Key Values
Principal maxima (d·sinθ = mλ)
m=0: 0°m=1: 7.9°m=2: 16.0°m=3: 24.4°m=4: 33.4°m=5: 43.4°
Fringe spacing (far field)λ/d = 0.138
1st diffraction min33.4°
Missing orders (a·sinθ = mλ)every 4.0th
Physics
Each slit acts as a Huygens point source emitting circular wavefronts. Constructive interference occurs when the path difference is an integer multiple of λ.
I ∝ [sin(Nδ/2) / (N·sin(δ/2))]² · sinc²(α/2)
δ = 2πd·sinθ/λ α = 2πa·sinθ/λ
Increasing N sharpens principal maxima. The slit width a modulates the envelope — orders that coincide with diffraction minima vanish (missing orders).