Snell/Descartes's Law (1636 Snell discovers Descarte's laws...)

 

Reflection and Refraction behaves according to Snell's laws which state:

One common Plane

The incoming ray, the surface normal, and the reflected ray all lie in a common plane.

One relation between angle

The angle that the reflected ray forms with the surface normal is determined by the angle that the incoming ray forms with the surface normal, and the relative speeds of light of the mediums in which the incident and reflected rays propogate according to the following expression.


DESCARTE'S DIOPTRICS, 1637

Reflection : a special case of the law

Reflection is a very special case of Snell's Law where the incident light's medium and the reflected rays medium is the same. Thus we can simplify the expression to:

 

1620s: Snell and Descarte, Snell’s Law : http://www.geo.hunter.cuny.edu/~afrei/theory_of_light_lecture.htm

SNELL'S LAW (FROM DESCARTE'S DIOPTRICS, 1637) : http://bayes.cs.ucla.edu/LECTURE/lecture_sec1.htm

1636 Snell discovers Descarte's laws... : unix.temple.edu/~meziani/history.pdf

Snell deduced his law from experimental data and thought that cosecants fitted his data best. The frenchman Descarte was the first to use the correct sines. In France it is known as Descarte's Law! http://www.star.le.ac.uk/~rw/courses/lect220.html

 

4  REFRACTIVE INDEX
n = [(speed vacuum )/(speed medium )] = [c/v]
It is a quantity that can be measured.
nglass = 1.52
nwater = 1.33
nair = 1.000292 at S.T.P.