Fresnel Diffraction at an Edge
In this Demonstration you can observe the interference pattern produced by light diffracted on a two-dimensional edge covering half of three-dimensional space. The distance from the edge can be adjusted in order to observe the intensity of light. This is an important example of Fresnel diffraction, which is a special case of the Kirchhoff diffraction theory. This is one of a small number of geometries for which the Fresnel diffraction equation can be solved analytically.