roughness factor (rugosity) 

of a surface
https://doi.org/10.1351/goldbook.R05419
The ratio: fr=ArAg where Ar is the real (true, actual) surface (interface) area and Ag is the geometric surface (interface) area.
Source:
PAC, 1986, 58, 437. (Interphases in systems of conducting phases (Recommendations 1985)) on page 439 [Terms] [Paper]
Citation: 'roughness factor' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.R05419 RIS BibTex EndNote
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Last revised: February 24, 2014