Snell's Law
Refraction
Snell's law (also called the Snell-Descartes law) is a formula used to calculate the refractive angle of light when crossing the separation surface between two different means of propagating light (with a different electromagnetic reflection). The name comes from its discoverer, the Dutch mathematician Willebrord Snel van Royen (1580-1626). The name "Snell" is due to his surname but they put two by his name Willebrord which carries two "l".
The same affirmation as the multiplication of the refractive index by the angle of incidence itself with respect to normality in constant for any relation of light incident on the surface separated from two media. That is, the component of the refractive index parallel to the surface is constant. Although Snell's law was formulated for the refraction phenomena of light, it can be applied to all types of waves by crossing a surface between two media in the speed of wave propagation.
History
Snell's law was first discovered by Ibn Sahl in the 10th century, who used it to solve the forms of anaclastic lenses (lenses that focus light with geometric aberrations). It was discovered again in the sixteenth century and enunciated again in the seventeenth century, by Willebrord Snel van Royen. In francophone countries, Snell's law is known as "the second law of contraction" or "law of Descartes".
Optical description
Consider two media characterized by refractive indices n1 and n2 (note that both media have different densities) separated by a surface S. The light rays that cross the two media are refracted or change their direction of propagation depending on the quotient between the refractive indexes n1 and n2
For a ray of light with an angle of incidence º1 in the first medium, angle between the normal to the surface and the direction of propagation of the ray, we will have that the ray propagates in the second medium with a refraction angle º2 whose value is obtained through Snell's law:
n1 sin º1 = n2 sinº2
n = c / v
Refractive index
It is called refractive index, the quotient between the speed of light in vacuum and the speed in light in a transparent material medium.
n = c / v
Snell's law of refraction is expressed in terms of the refractive index
n1 · sinθ1 = n2 · sinθ2
In the following table, it refers to the refractive indexes of the category
Substance Refractive index (sodium D line)
Sugar 1.56
Diamond 2.417
Mica 1.56-1.60
Benzene 1,504
Glycerin 1.47
Water 1,333
Ethyl alcohol 1,362
Olive oil 1.46
Refraction and reflection
Image that shows the refraction and reflection of light when reaching a medium, the amount of reflected and refracted light is generally 50%, however, there are coatings (thin films) that can vary these percentages.
Refraction is the change of direction that a wave experiences when passing from one material medium to another. It only occurs if the wave strikes obliquely on the separation surface of the two media and if they have different refractive indices. The refraction originates in the change of speed of propagation of the wave, when it passes from one medium to another.
Reference
Wikipedia. 2018. Ley de Snell. [Online] 05 01, 2018. [Cited: 05 10,
2018.] https://es.wikipedia.org/wiki/Ley_de_Snell.
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