When a wave passes through a slit or around a corner, it spreads out — diffraction. The smaller the slit, the more spreading.
Drag the sliders
y = pow(sin(a · x) / (a · x + 0.0001), 2)
Single-slit minima
a = slit width, m = 1, 2, 3… The narrower the slit (small a) or the longer the wavelength, the wider the central bright band spreads.
Where you see it
- Sound bending around a doorway — you hear someone before you see them.
- Ocean swell fanning out past a harbour gap.
- The rainbow sheen off a CD — a grating of tiny tracks.
- The blur limit of telescopes and microscopes ('diffraction limit').
Diffraction is strongest when the obstacle or opening is comparable in size to the wavelength — that's why radio (long λ) bends around buildings but visible light (tiny λ) casts sharp shadows.