
6
POLARIZED LIGHT
In the 1600s, Huygens [22] recognized that there are “two kinds of light.” Snell’s law of refrac-
tion, which had recently been discovered empirically, related the bending of light across a
boundary to a quantity called the index of refraction. In some materials Huygens observed
light refracting in two different directions. He assumed, correctly, that the two different kinds
of light had different indices of refraction. Almost 200 years later, Young [25] provided an
understanding in terms of transverse waves that shortly preceded Maxwell’s unication of the
equations of electromagnetics.
Today, the principles of polarization are used ...