Moiré Pattern of Two Equally Spaced Circular Ring Patterns
The Moiré pattern formed using two displaced equally spaced circular ring patterns illustrates the interference fringes produced by interfering two spherical waves. The spacing of the Moiré pattern depends on the separation between the centers of the two circular ring patterns, just like the spacing of interference fringes depends upon the separation between the two point sources. This Demonstration shows the shape of the interference fringes in a plane containing the two point sources.
Moiré patterns are a good way to illustrate the interference of two wavefronts. Moiré patterns show the difference between the two original patterns just like interference fringes show the phase difference between two interfering wavefronts. When the two patterns are in phase, bright regions result and when the patterns are a half-period out of phase, dark regions result.