## specular reflectance (reflection factor), $$\rho$$

in optical spectroscopy
https://doi.org/10.1351/goldbook.S05851
radiant power specularly reflected from the surface of a system, P refl, divided by the incident power, P 0: $\rho =\frac{P_{\mathrm{refl}}}{P_{0}}$
Source:
PAC, 1985, 57, 105. 'Names, symbols, definitions and units of quantities in optical spectroscopy (Recommendations 1984)' on page 115 (https://doi.org/10.1351/pac198557010105)