polarization of light. in electrodynamics, polarization is the property of electromagnetic wave,...
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Polarization of light
In electrodynamics, polarization is the property of electromagnetic wave, such as light , that describes the direction of the transverse Electric field
E
B
k
0ˆ( , ) cos( )x xE z t iE kz t
0ˆ( , ) cos( )y yE z t jE kz t
( , ) ( , ) ( , )x yE z t E z t E z t
For
0 0
( 0, 2, 4, 6.....)
ˆ ˆ( ) cos( )x y
n n
E iE jE kz t
0 0
( 1, 3, 5.....)
ˆ ˆ( ) cos( )x y
n n
E iE jE kz t
Linearly polarized light
xx
y
y
y
y
xx
0
2 ( 0, 1, 2, 3.....)2
ˆ ˆ[( cos( ) sin( )]
n n
E E i kz t j kz t
Right circularly polarized light
Circularly polarized light
)tkz(Ei)t,z(Ex cos0
0ˆ( , ) cos( )yE z t jE kz t
Time
/4
t=0
t=/4
t=/2
t=3/4
Referen
ce ax
is
x
y
E0
xE
yE
t
0kz
E
For kz=/4
)tkz(Ei)t,z(Ex cos00ˆ( , ) sin( )yE z t jE kz t
Left circularly polarized light
0
2 ( 0, 1, 2, 3.....)2
ˆ ˆ( cos( ) sin( )]
n n
E E i kz t j kz t
0
0
cos( )
cos( )x x
y y
E E kz t
E E kz t
2 2
2
0 0 0 0
0 0
2 20 0
2 cos sin
2 costan 2
y yx x
y x y x
x y
x y
E EE E
E E E E
E E
E E
Elliptical polarized light
EyE0
xE0
State of Polarization
Plane polarized light : P state
Right circularly polarized light : R state
Left circularly polarized light : L state
Elliptically polarized light : E state
Natural Light
An ordinary light source consists of a very large number of
randomly oriented atomic emitters, which radiates a polarized
wavetrain for roughly 10-8 sec.
Completely polarized
Completely unpolarized
Partially polarized
Degree of polarization
UP
P
II
IP
Malus’s law
Unpolarized light2
0 0(0) cos 2I I I
Malus’s law
2)cos0(II 20(0)
2
EI
Polarizers
Selective absorption or dichorism
Double refraction or birefringes
Reflection
Scattering
Polarization by scattering
Scattering of polarized light by a molecule
Scattering of unpolarized light by a molecule
Why sky looks blue
EarthA
B
C
Blue Sky
Rayleigh scattering4
1
Red Orange Yellow Green Blue Violet
1 2 2.5 3 6 10
Red Sunset
Dust layer
EarthA
B
C
D
White Sun in Blue Sky
Yellow Sky
Red Sunset