Editing Rayleigh scattering (section)

==In porous materials==
[[File:Why is the sky blue.jpg|thumb|Rayleigh scattering in [[Opalescence|opalescent]] glass: it appears blue from the side, but orange light shines through.<ref>[http://www.webexhibits.org/causesofcolor/14B.html Blue & red | Causes of Color]. Webexhibits.org. Retrieved on 2018-08-06.</ref>]]
Rayleigh-type ''λ''<sup>−4</sup> scattering can also be exhibited by porous materials. An example is the strong optical scattering by nanoporous materials.<ref name = Svensson>{{cite journal|doi=10.1063/1.3292210|title=Laser spectroscopy of gas confined in nanoporous materials|journal=Applied Physics Letters|volume=96|issue=2|pages=021107|year=2010|last1=Svensson|first1=Tomas|last2=Shen|first2=Zhijian|url=http://lup.lub.lu.se/search/ws/files/2070270/2370765.pdf|bibcode=2010ApPhL..96b1107S|arxiv=0907.5092|s2cid=53705149}}</ref> The strong contrast in refractive index between pores and solid parts of sintered [[alumina]] results in very strong scattering, with light completely changing direction each five micrometers on average. The ''λ''<sup>−4</sup>-type scattering is caused by the nanoporous structure (a narrow pore size distribution around ~70&nbsp;nm) obtained by [[sintering]] monodispersive alumina powder.