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Chapter 6: Optics
27
with
I
=
±

±
S

²
it follows:
R
+
T
=1
. A special case is
r
±
=0
. This happens if the angle between the reFected
and transmitted rays is
90
◦
. ±rom Snell’s law it then follows:
tan(
θ
i
)=
n
. This angle is called
Brewster’s
angle
. The situation with
r
⊥
is not possible.
6.6
Polarization
The polarization is de²ned as:
P
=
I
p
I
p
+
I
u
=
I
max

I
min
I
max
+
I
min
where the intensity of the polarized light is given by
I
p
and the intensity of the unpolarized light is given by
I
u
.
I
max
and
I
min
are the maximum and minimum intensities when the light passes a polarizer. If polarized
light passes through a polarizer
Malus law
applies:
I
(
θ
I
(0) cos
2
(
θ
)
where
θ
is the angle of the polarizer.
The state of a light ray can be described by the
Stokesparameters
: start with 4 ²lters which each transmits half
the intensity. The ²rst is independent of the polarization, the second and third are linear polarizers with the
transmission axes horizontal and at
+45
◦
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 Spring '10
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