Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Back to the OSAC Lexicon

Retardation (R)

the actual distance between two doubly refracted rays as they emerge from an anisotropic fiber; dependent upon the difference in the two refractive indices, |n||n|, and the thickness of the fiber.

Date Added to Lexicon
Standard Source (Designation Number Title of Standard. Publisher, Place, Year.)
ANSI/ASTM E2228-23a Standard Guide for Microscopical Examination of Textile Fibers. ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428, 2023. Source link
Reprinted, with permission, from ASTM, copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be purchased from ASTM International, https://www.astm.org