coherence length

Coherence length is the distance over which a light wave maintains a consistent phase relationship, meaning its wave pattern stays predictable. Think of it as the length over which the light wave remains "in sync." Beyond this distance, the wave's phase becomes random, and it no longer behaves like a single, stable wave. This concept is important in applications like lasers and interferometers, where maintaining phase relationships over certain distances is crucial for precise measurements and interference effects. In essence, coherence length measures how far light can travel while staying "coherent" and useful for wave-based technologies.