Monday, June 29, 2015

Snell’s law of refraction

Snell’s Law was discovered by various investigators over the centuries. In antiquity, optics began when Egyptians and Mesopotamians developed the first lenses with impressive mechanism based on reflection. Perhaps the first person to understand the basic relationship expressed by Snell’s Law was the Arabian mathematician Ibn Sahl in the year 984.
Abu Sa’d al-Ala Ibn Sahl 
Based on catoptrics and the study of burning mirrors and lenses, Abu Sa’d al-Ala Ibn Sahl (940-1000) devised a systemic elaboration of the fundamentals of dioptrics.

It is believed that Ibn Sahl established a principle akin to the so-called ‘Snell’s Law’ of refraction. Ibn Sahl shows that every transparent medium, including the ‘celestial sphere’ has a certain degree of opacity.

Ibn Sahl described a law of refraction in his treatise ‘On burning mirrors and lenses.’

In 1602, English astronomer and mathematician Thomas Harriot discovered the law but he did not publish his work.
Snellius Willebrord
In 1621, Snellius Willebrord discovered the law. It expresses the relationship between the path of a ray of light passing through the boundary of two adjacent substances and their respective refractive indices.  His unpublished notes on the subject were discovered by the Dutch scholar and manuscript collector Isaac Vossius around 1662.

Christiaan Huygens read unpublished equation by Snell and discussed the law in his Dioptrica, published in 1703.
Snell’s law of refraction


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