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Updated: Jan 8, 2026

Scattering And Absorption of Light in Planetary Regoliths
Published on: July 1, 2019
Observation of mean path length invariance in light-scattering media
Romolo Savo1, Romain Pierrat2, Ulysse Najar1
1Laboratoire Kastler Brossel, École Normale Supérieure-Paris Sciences et Lettres (PSL) Research University, CNRS, Université Pierre et Marie Curie-Sorbonne Universités, Collège de France, 24 rue Lhomond, 75005 Paris, France.
Abstract:
The microstructure of a medium strongly influences how light propagates through it. The amount of disorder it contains determines whether the medium is transparent or opaque. Theory predicts that exciting such a medium homogeneously and isotropically makes some of its optical properties depend only on the medium's outer geometry. Here, we report an optical experiment demonstrating that the mean path length of light is invariant with respect to the microstructure of the medium it scatters through. Using colloidal solutions with varying concentration and particle size, the invariance of the mean path length is observed over nearly two orders of magnitude in scattering strength. Our results can be extended to a wide range of systems-however ordered, correlated, or disordered-and apply to all wave-scattering problems.
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