Fast and Slow Rays
| Propagation direction |
Ordinary ray | Extraordinary ray | ||
|---|---|---|---|---|
| Polarization | neff | Polarization | neff | |
| z | xy-plane | n/a | n/a | |
| xy-plane | xy-plane | z | ||
| xz-plane | y | xz-plane | ||
| other | analogous to xz-plane | |||
For a given propagation direction, in general there are two perpendicular polarizations for which the medium behaves as if it had a single effective refractive index. In a uniaxial material, rays with these polarizations are called the extraordinary and the ordinary ray (e and o rays), corresponding to the extraordinary and ordinary refractive indices. In a biaxial material, there are three refractive indices α, β, and γ, yet only two rays, which are called the fast and the slow ray. The slow ray is the one for which the material has the highest effective refraction index.
For a uniaxial material with the z axis defined to be the optical axis, the effective refractive indices are as in the table on the right. For rays propagating in the xz plane, the effective refractive index of the e polarization varies continuously between and, depending on the angle with the z axis. The effective refractive index can be constructed from the index ellipsoid.
Read more about this topic: Birefringence
Famous quotes containing the words fast, slow and/or rays:
“On the beach at night,
Stands a child with her father,
Watching the east, the autumn sky.
Up through the darkness,
While ravening clouds, the burial clouds, in black masses spreading,
Lower sullen and fast athwart and down the sky,”
—Walt Whitman (1819–1892)
“The Cretans are always liars, evil beasts, slow bellies.”
—Bible: New Testament St. Paul, in Titus, 1:12.
Cited by Paul, this remark is attributed to Epimenides.
“The spirit of God, like the sun, always gives all its light at once. The spirit of man resembles the pale moon, which has its phases, its absences and its returns, its lucidity and its spots, its fullness and its disappearance, which borrows all its light from the rays of the sun, and which still dares to intercept them on occasion.”
—Victor Hugo (1802–1885)