Interference Patterns - Waves from Two Slits

Waves diffracted by two narrow slits interfere with each other constructively and destructively to form interference patterns that resemble those from two point sources.

Discussion

As we have seen, a narrow opening in a barrier acts as a point source for waves passing through. If there are two or more such openings in a barrier that are close to each other, circular waves from each overlap each other and interact to form what are called diffraction or interference patterns. While the patterns formed with two openings resemble the interference patterns of waves from two point sources (see the section Waves in a Ripple Tank), they are not as clearly defined. Because the amount of energy carried by that part of water waves that passes through two narrow openings is much less than that carried by waves generated by two point sources, two-slit wave amplitudes are smaller, so interference patterns are less distinct.