https://doi.org/10.1351/goldbook.R05235

Fraction of incident radiation reflected by a surface or discontinuity, ρ λ = P λ refl P λ 0, where Pλ0 and Pλrefl are, respectively, the incident and reflected spectral radiant power.**Note: **

The reflectance for a beam of light normally incident on a surface separating two materials of refractive indices n 1 and n 2 is given by \[\rho(\lambda) = \frac{\left ( n_{1}\,-\,n_{2}\right )^{2}}{\left ( n_{1}\,+\,n_{2} \right )^{2}}\] Reflectance increases as the @A00346@ of incidence decreases from 90 degrees.*Source: *

PAC, 2007,*79*, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 413 (https://doi.org/10.1351/pac200779030293)

The reflectance for a beam of light normally incident on a surface separating two materials of refractive indices n 1 and n 2 is given by \[\rho(\lambda) = \frac{\left ( n_{1}\,-\,n_{2}\right )^{2}}{\left ( n_{1}\,+\,n_{2} \right )^{2}}\] Reflectance increases as the @A00346@ of incidence decreases from 90 degrees.

PAC, 2007,