Double-slit Interference Simulation
This simulation recreates Young's experiment for waves in general, letting you vary the slit spacing and wavelength and watch the fringe pattern respond on the screen behind.
How to use this simulation
- Change the slit separation and wavelength
- Move the screen closer or further away
- Show the path difference to any chosen point
What to look for
- Narrowing the slit separation widens the fringe spacing
- The central fringe is always bright, since the path difference there is zero
- Fringe positions depend on wavelength, so white light spreads them into colours
The physics behind it
Waves from the two slits travel different distances to each point on the screen. Where the path difference is nλ they arrive in phase and reinforce; where it is (n + ½)λ they cancel. Fringe spacing is w = λD/d, so closer slits and longer wavelengths both spread the fringes further apart.