Optical path length, abbreviated as \(OPL\), is the effective distance that light travels through an optical system after accounting for the optical properties of the materials along its path. Unlike ordinary geometric distance, which measures only the physical length between two points, optical path length also includes the effect of the material's refractive index, which determines how much the material slows the propagation of light. Optical path length is used in wave optics, fiber optics, astronomy, and optical engineering because it determines how the phase of light changes as it propagates through different media.
Optical Path Length Formula |
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\( OPL \;=\; n \cdot d \) (Optical Path Length) \( n \;=\; \dfrac{ OPL }{ d }\) \( d \;=\; \dfrac{ OPL }{ n }\) |
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| Symbol | English | Metric |
| \( c \) = Optical Path Length | \(ft\) | \(m\) |
| \( n \) = Refraction Index | \(dimensionless\) | \(dimensionless\) |
| \( d \) =Geometric (Physical) Path Length | \(ft\) | \(m\) |
