Diffraction by Opaque Edges

The beam of a laboratory helium-neon laser was spread with a telescope eyepiece and directed at machined metal edges. The diffraction pattern was photographed on a screen approximately four meters from the edge. This is diffraction from the corner of a double-edged razor blade.

This diffraction pattern is from the cutout in the razor blade imaged above. Barrier diffraction must be handled by the techniques of Fresnel diffraction. One way to approach the calculation is by use of the Cornu spiral.