fast-vibration direction

fast-vibration direction

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