🌊 Diffraction & Interference
A plane wave strikes a barrier with one or more slits. Each slit acts as a new wave source (Huygens' principle), and the wavelets interfere to form a characteristic intensity pattern on a distant screen. Young's double-slit: I = I₀ cos²(πd sinθ/λ) sinc²(πa sinθ/λ).
Slit Type
Wave Parameters
Stats
What this simulation shows
The left side shows a plane wave (parallel wavefronts). The grey barrier blocks the wave except at the slit opening(s). On the right side each slit radiates circular Huygens wavelets. Where crests meet, the waves reinforce (bright); where crest meets trough, they cancel (dark). The yellow curve on the far right shows the Fraunhofer intensity I(y) calculated analytically.
Single slit — broad central maximum, narrowing as
slit width increases.
Double slit — close interference fringes modulated by
the single-slit envelope.
Grating — sharp bright maxima that tighten as N
increases.
Did you know?
Thomas Young's 1801 double-slit experiment was the first direct proof that light behaves as a wave. Modern diffraction gratings with thousands of slits per millimetre are used in spectrometers, CD/DVD drives, and laser printers.