1581-1626. Dutch mathematician and physicist
who devised the basic law of refraction,
known as Snell's law, in 1621. This states
that the ratio between the sine of the angle
of incidence and the sine of the angle of
refraction is constant. The laws describing
the reflection of light were well known in
antiquity, but the principles governing the
refraction of light were little understood.
Snell's law was published by Descartes in
1637.