Zero-order fringe

A zero-order fringe occurs in interferometry, where two light waves combine to create a pattern of bright and dark bands called fringes. The zero-order fringe is the central bright band with no phase difference between the waves, meaning they are perfectly in sync at this point. It's like the point where the two wave peaks align exactly. This fringe is typically the most intense and serves as a reference point for measuring tiny changes or differences in the path length of the light beams, helping scientists analyze small variations in a system with high precision.