of a surface
https://doi.org/10.1351/goldbook.R05419
The ratio: \[f_{\text{r}}=\frac{A_{\text{r}}}{A_{\text{g}}}\] where \(A_{\text{r}}\) is the @R05193-1@ (true, actual) @R05193-2@ and \(A_{\text{g}}\) is the @E02282@.
Source:
PAC, 1986, 58, 437. (Interphases in systems of conducting phases (Recommendations 1985)) on page 439 [Terms] [Paper]