Becke line method
method for determining the refractive index of a transparent particle relative to its mountant by noting the direction in which the Becke line moves when the focus is changed.
DISCUSSION—The Becke line always moves toward the higher refractive index medium (particle or mountant) when the focus is raised, and towards the lower refractive index medium when the focus is lowered. At the point where the index of the particle matches the index of the mounting medium, the Becke line is no longer visible. The Becke line is generally viewed at a wavelength of 589 nm (the D line of sodium [nD]).
Committee
Interdisciplinary
Date Added to Lexicon
Standard Source (Designation Number Title of Standard. Publisher, Place, Year.)
ANSI/ASTM E1732-25 Standard Terminology Relating to Forensic Science . ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428 , 2025.
Source link
Reprinted, with permission, from ASTM E1732-24e1 Standard Terminology Relating to Forensic Science, copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard is available from ASTM International, https://www.astm.org