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Surface Reflection and Polarization
Name: Tony K.
Status: student
Age: 17
Location: N/A
Country: N/A
Date: 2001-2002
Question:
I was studying on polarization of light and came across
Brewster's angle. Even after much research on the Internet, I cannot
find out WHY polarization occurs parallel to the surface along this
angle. Why does it work? What is happening that my eyes cannot see?
Replies:
Tony,
Brewster's angle is the angle at which reflected light is perpendicular to
refracted light (the light that continues on into the material). The effect
of pure polarization at Brewster's angle was discovered by experiment: no
theories predicted it. There are some theories regarding it, but nobody
knows for sure why it happens. The most popular theory is as follows:
The electric charges in the glass (or other transparent material) oscillate
perpendicular to the direction of the light waves within the material.
Thus, they oscillate perpendicular to the refracted light. Because light
waves are "side-to-side" oscillations (lateral waves), there must be some
side-to-side motion in the charges producing the waves. When the reflected
light is perpendicular to the refracted light, there is no oscillation in
the reflection plane. Waves oscillating in the plane of reflection cannot
be emitted as reflected light.
Dr. Ken Mellendorf
Physics Instructor
Illinois Central College
The answer is simple in principle, but a bit more complicated in the
details. The reflection and refraction of light by a surface is not simply
the "bouncing off" of the incident beam from the surface. Rather, the
oscillating electric vector of the incident beam causes the electrons in the
reflecting/refracting medium to oscillate. These oscillations in turn
produce the reflected/refracted beams. In the "particle" description of
light replace the "oscillation of the electrons of the medium" to "elastic
scattering of the photons by the electrons in the medium". That is the
simple part.
The details are a bit more involved, but are explained far more concisely
and lucidly than I would even attempt. See: Richard Feynman's "Lectures on
Physics"
Vol. I, Chapter 33, Sections 33-4 through 33-7.
Vince Calder
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Update: June 2012
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