Polarization of light. In electrodynamics, polarization is the property of electromagnetic wave, such as light, that describes the direction of the transverse.

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