https://doi.org/10.1351/goldbook.08577
Collections of solid particles that are transparent to electromagnetic radiation of a particular wavelength and are slightly larger than the wavelength of the radiation transmit poorly due to reflection and scattering from the interfaces. The transmission increases markedly at wavenumbers at which the refractive index of the particles is close to that of the surrounding medium.
Note:
The Christiansen effect frequently causes strong absorption bands from coarsely ground particles to be distorted due to the change in refractive index associated with the anomalous dispersion of the refractive index through the absorption region.
The Christiansen effect frequently causes strong absorption bands from coarsely ground particles to be distorted due to the change in refractive index associated with the anomalous dispersion of the refractive index through the absorption region.