Optical Path Length (Optical path = n × geometric path)
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Optical path = n × geometric path
What each symbol means
| Symbol | What it stands for |
|---|---|
| n | Refractive index of the medium |
| \Delta x | Geometric path length (m) |
| \Delta_{\text{opt}} | Optical path length (m) |
When to use this
Light takes same time to travel optical path in vacuum as geometric path in medium. Phase difference = (2π/λ)×optical path. Crucial for interference calculations with glass slabs. Extra optical path by slab of thickness t: (n-1)t.