Young's Double-slit Interference Simulation
Young's double-slit experiment settled the argument about whether light is a wave. This simulation recreates it, letting you vary the slit spacing and wavelength while the fringe pattern on the screen adjusts in real time.
How to use this simulation
- Change the slit separation and the slit-to-screen distance
- Select different wavelengths across the visible spectrum
- Switch between single-slit and double-slit patterns
What to look for
- Fringes spread out when the slits are brought closer together
- Red light gives wider fringe spacing than blue, since spacing scales with wavelength
- The central fringe sits directly opposite the midpoint of the slits and is always bright
The physics behind it
Light passing through two narrow slits spreads by diffraction and overlaps beyond them. Bright fringes appear where the path difference is a whole number of wavelengths, giving fringe spacing w = λD/d, with D the slit-to-screen distance and d the slit separation. Only a wave model predicts these fringes; a stream of particles would produce two bright bands.