refraction effects

https://doi.org/10.1351/goldbook.R05239
The luminescence flux emitted from the interior of a rectangular sample reaching a photodetector place at some distance from the sample is decreased by a factor of approximately \(n^{2}\) (where \(n\) is the refractive index of the medium) compared with a medium whose refractive index is 1.0. Such effects are termed refraction effects.
Source:
PAC, 1984, 56, 231. 'Nomenclature, symbols, units and their usage in spectrochemical analysis-Part VI: molecular luminescence spectroscopy' on page 244 (https://doi.org/10.1351/pac198456020231)