Wave Interference

Two coherent sources in 2D produce an interference pattern of constructive and destructive regions. Adjust separation and wavelength to see how fringe spacing changes.

Who it's for: Physical optics and waves; Young’s experiment and path-difference reasoning.

Key terms

  • interference
  • path difference
  • constructive
  • destructive
  • coherence

How it works

Two coherent point sources in a square ripple tank (top view). The field is the sum of two outgoing circular waves; interference creates quasi-hyperbolic nodal lines and curved maxima. Toggle decay to mimic cylindrical spreading.

Key equations

η = A₁ sin(kr₁ − ωt) + A₂ sin(kr₂ − ωt)
Path difference Δr = r₂ − r₁: constructive when kΔr ≈ 2πn, destructive near kΔr ≈ (2n+1)π (same amplitude).

Frequently asked questions

What causes bright and dark regions?
Where crests from both sources meet in phase, amplitude adds (constructive interference); where they arrive out of phase, cancellation reduces amplitude (destructive interference).