Quantifying the "milky sky" experiment.
Spectra of direct and scattered light that passed through a tank of water mixed with up to 25 ml of homogenized skim milk were measured with a spectroradiometer in a classic experiment used to illustrate why the sky is blue and why the Sun turns red near the horizon. The direct light penetrating the tank was reddened by preferential scattering of short waves by the milk particles (protein casein micelles and fat globules). Scattered light was blue near the light source when the optical thickness was small and red far from the source when the optical thickness was large. The measured radiance spectra and Mie theory were used to estimate that the optically effective mean diameters of protein casein micelles and fat globules were 170 and 610 nm.
Gedzelman
Stanley David
SD
Departamento de Optica, Universidad de Granada, 18071 Granada, Spain. stan@sci.ccny.cuny.edu
López-Alvarez
Miguel Angel
MA
Hernandez-Andrés
Javier
J
Greenler
Robert
R
D001256:Astronomy / Q000379:methods*; D002364:Caseins / Q000737:chemistry; D004867:Equipment Design; D006017:Glycolipids / Q000737:chemistry; D006023:Glycoproteins / Q000737:chemistry; D008027:Light; D066292:Lipid Droplets; D008823:Micelles; D008962:Models, Theoretical; D055095:Optics and Photonics; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D016082:Solar System; D013053:Spectrophotometry / Q000379:methods
D002364:Caseins; D006017:Glycolipids; D006023:Glycoproteins; D008823:Micelles; C110367:milk fat globule