Willebrord von Roijen Snell

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Willebrord von Roijen Snell
Reference 1
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Life Facts

• Born 1591 in Leiden, Netherlands.
• Born into a rich family. Son of a
  Mathematician/Linguist
• Entered the university of Leiden intending to
  study Law.
• At the age of 11, he was lecturing in mathematics
  at the University
• At a young age, he traveled extensively over
  Europe, visiting astronomers.
• This date is disputed somewhat with 1580 being
  the other common date.

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Curriculum vitae

• Succeeded his father in 1613 as professor of
  mathematics
• He was one of the first to apply mathematics
  extensively in astronomy.
• 1617 published Eratosthenes Batavus methods for
  measuring the Earth
• Tiphys batavus published in 1624 concept of
  Loxodrome
• Geometrically computed p to 7 digits

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Calculation of Earths Circumference

• 1 degree of the meridian
• 55,100 toises 117,449 yards
• After some correction 57,033 toises 121,569
  yards
• Actual 121,740.911yards
• An error of less than 1 percent

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Snells Law of Refraction

• Snell discovered Law of Refraction in 1621
• N1sin T1 N2sin T2
• Chemical Composition as well as incident angle
  determines angle of refraction.
• Snells name not attributed to the law 1703, when
  Huygens published Dioptrica

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The Debate

• it was first published by French mathematician
  and philosopher René Descartes (1596-1650) under
  the name Law of Sines in his 1637 work La
  Dioptrique. It seems probable that Descartes did
  not develop his Law of Sines independentlyand so
  whether this law is called Snells Law or
  Descartes Law of Sines really depends on whether
  or not you are French.
• From PhotoNotes.org Snells Law

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Bibliography 1 Science World,
http//scienceworld.wolfram.com/biography/Snell.
html, 20- Sep-04 2 PhotoNotes,
http//photonotes.org/cgi-bin/entry.pl?idSnells
law, 20-Sep-04 3 LoveToKnow Encyclopedia,
http//85.1911encyclopedia.org/S/SN/SNELL_WILLEBR
ORD.htm, 20-Sep-04

• By Marshall Hart
• Adapted from a presention by
•   Marian B. McKenzie and Walter Fox Smith