Willebrord Snel (1580–1626) Netherlands. "Although he discovered the law of refraction, a basis of modern geometric optics, in 1621, he did not publish it and only in 1703 did it become known when Huygens published Snell's law in Dioptrica." Snell also studied navigation and proposed the method of triangulation, which is the foundation of geodesy (the branch of mathematics dealing with the measurement of features on the earth). For some reason, the law named after the man is spelled incorrectly. Snel the man vs. Snell the law.
|sin θi||= constant|
n1 sin θ1 = n2 sin θ2
"This form of Snell's law was actually published by René Descartes (1596–1650) France in La Dioptrique (1637). Snell did discover the relationship but articulated it in a different way. Today it is the form used by Descartes that is called Snell's law."
The index of refraction.
|n =||index of refraction|
|c =||speed of light in a vacuum|
|v =||speed of light in a medium|
The index of refraction is somewhat related to density, as one would expect. This graph is for transparent minerals. Someone should make one for liquids and see what happens.
|air (15 ℃)||1.00030942||helium (liquid)||??|
|air ( 0 ℃)||1.00029238||hydrogen (gas)||1.000140|
|air (+15 ℃)||1.00027712||hydrogen (liquid)||1.0974|
|air (+30 ℃)||1.00026337||lucite||1.495|
|air (+60 ℃)||1.00023958||milk||1.35|
|alcohol, ethyl (grain)||1.361||oil, microscope||1.515|
|alcohol, methyl (wood)||1.328||oil, vegetable (50 ℃)||1.47|
|butter (40 ℃)||1.455||quartz, crystalline||1.544|
|butter (60 ℃)||1.447||quartz, fused silica||1.4585|
|cocoa butter (40 ℃)||1.457||sapphire||1.76|
|emerald, synth flux||1.561||ulexite||1.49|
|emerald, synth hydro||1.568||vacuum||1 exactly|
|eye, cornea||1.38||water (ice)||1.309|
|eye, aqueous humor||1.33||water (liquid, 0 ℃)||1.33346|
|eye, lens cover||1.38||water (liquid, 20 ℃)||1.33283|
|eye, lens||1.41||water (liquid, 100 ℃)||1.31766|
|eye, vitreous humor||1.34||water (vapor)||1.000261|
|glass, borosilicate (pyrex)||1.474||zirconia, cubic||2.173|
|glass, crown (soda-lime)||1.512|
|glass, flint (29% lead)||1.569|
|glass, flint (55% lead)||1.669|
|glass, flint (71% lead)||1.805|
|glass, fused silica||1.4585|
Don't go in the water.