Optical path length (OPL) is defined as the product of the geometric length a light ray travels and the refractive index of the medium through which it passes.
Key points:
- It represents the effective distance light travels considering how the medium slows it down compared to vacuum.
- Mathematically:
OPL = refractive index (n) × physical distance (d) - Important in analyzing interference, diffraction, and phase changes in optical systems.
- Two different paths with the same optical path length cause constructive interference.
Why it matters:
Optical path length helps predict how light waves combine or cancel out after traveling different routes, fundamental in designing lenses, interferometers, and fiber optics.