IEVref: 705-02-14 ID: Language: en Status: Standard Term: optical path length Synonym1: phase path length [Preferred] Synonym2: Synonym3: Symbol: Definition: length of the path that would be travelled at the speed of light in vacuum in a duration equal to the phase delay of a given electromagnetic wave between two given points Note 1 to entry: Between two points in the same ray path, the optical path length equals the line integral of the refractive index along the ray path: $\underset{c}{\int }n\text{d}s$ where n is the refractive index of the medium at each point in the direction of the path and ds the curve element along the path. Publication date: 2020-04 Source: Replaces: 705-02-14:1995-09 Internal notes: CO remarks: TC/SC remarks: VT remarks: Domain1: Domain2: Domain3: Domain4: Domain5: