slow-vibration direction

slow-vibration direction

[′slō vī′brā·shən di‚rek·shən]
(optics)
The direction of the electric field vector of the ray of light that travels with the smallest velocity in an anisotropic crystal and therefore corresponds to the maximum refractive index.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.