The double-slit experiment is one of the most famous experiments in physics. It demonstrates that matter and energy such as light can exhibit both wave and particle characteristics - known as the particle-wave duality of matter -depending on the scenario.
This simulation presents the interference effects in light waves. Two light rays pass through two slits, separated by a distance, d, and strike a screen a distance, L, from the slits. You can change these parameters and you see the result of interference on the screen. An excellent tool for teaching and learning.