What is the definition of interference in optics?

Interference in optics refers to a phenomenon where overlapping light waves create a new wave pattern. This occurs when two or more coherent light waves, which are waves having a constant phase relationship, combine. The superposition of these waves results in a new distribution of intensity, characterized by regions of constructive interference (where the waves reinforce each other, leading to increased brightness) and destructive interference (where the waves cancel each other out, resulting in darkness).

This principle is fundamental to various optical applications, including the creation of interference fringes in experiments like the double-slit experiment, which demonstrates the wave nature of light. The other definitions do not describe interference; the merging of light rays into a single beam relates more to focusing or refraction, reflection pertains to light bouncing off surfaces, and absorption is about light being taken in by a material. These phenomena are distinct and do not involve the pattern formation that characterizes interference.