Before revision: The range of separation between the two points over which there is significant interference defines the diameter of the coherence area, Ac (Coherence length , often a feature of a source, is usually an industrial term related to the coherence time of the source, not the coherence area in the medium.)
After revision: The range of separation between the two points over which there is significant interference defines the diameter of the coherence area, , (Coherence length , often a feature of a source, is usually an industrial term related to the coherence time of the source, not the coherence area in the medium.)