56
1 Polarization 1

1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Embed Size (px)

Citation preview

Page 1: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

1

Polarization

1

Page 2: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Polarisation

XY – Plane: Plane of polarisation

Page 3: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

S =(E x B)/μo

Page 4: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Unpolarized light

Polaroid: Transmits along the pass axis and absorbs along the perpendicular axis

Page 5: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Malus law 222 cos)cos( oo IEEI

Page 6: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Unpolarized light2

cos2 oo

III

Page 7: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Degree of polarisationIf the incident light is a mixture of unpolarised light of intensity Iuand polarised light of intensity Ip, then the transmitted light is given by:

2cos2 pu I

II

2 ;

2 minmaxu

pu I

III

I

minmax

minmax

II

IIP

Page 8: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Polarisation by scattering

Page 9: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Rayleigh scattering

Blue sky

Red Sunset / Sunrise

Page 10: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Convention

Page 11: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

- Polarisation

Plane of polarisation is same as plane of incidence

- Polarisation

Plane of polarisation is perpendicular to the plane of incidence

Page 12: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Polarisation by reflection

Page 13: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Brewster angle

Glasspartially polarised

linearly polarised

unpolarised polarised

Page 14: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Brewster angle

Page 15: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

= Brewster angle

Brewster’s law

Page 16: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Polarisation by reflection

Page 17: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Polarisation by double refraction- Two refracted beams emerge instead of one- Two images instead of one

Calcite Quartz

Optic Axis: Uniaxial crystals exhibit cylindrical symmetry. There is a unique direction in a uniaxial crystal called the optic axis.Values of physical parameters along optic axis are different from the values perpendicular to it.

Page 18: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Calcite

Extraordinary rayOrdinary ray

Optic axisPrincipalPlane:

Plane contains optic axis and the

direction of propagation

Page 19: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

CalcitePolariser/Analyser

Ordinary rayσ - polarised

Page 20: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Extraordinary rayπ - polarised

Calcite

Page 21: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Polarisation by double refraction

Isotropic Medium : Velocity Spherical

Uniaxial and Biaxial CrystalsUniaxial : Calcite, Quartz

Biaxial: Mica

Anisotropic Medium : Velocity ellipsoid

Page 22: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

- PolarisationPlane of polarisation is same as

plane of incidence (principal plane)

- PolarisationPlane of polarisation is perpendicular

to the plane of incidence (principal plane)

Plane of incidence : plane contains incident ray, reflected/refracted ray, surface normal

Plane of polarisation : plane contains electric field vector and direction of propagation

Principal plane : Plane contains optic axis and the direction of propagation

This definitionis considered in absence of Principal Plane

Page 23: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

e-ray : Plane of polarisation is same as principal plane

Plane of polarisation is perpendicular to the principal plane

o-ray :

e-ray in general does not obey the laws of refraction except in case of special cut of crystal (optic axis)

o-ray always obeys the laws of refraction

Always e-ray carries -polarisation and o-ray carries -polarisation

Page 24: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Positive and Negative uniaxial crystals

Quartz - Positive (ne - no)>0

Calcite - Negative (ne - no)<0

no = 1.5443 ne = 1.5534

ne = 1.4864no = 1.6584

For sodium D lines

Linear polarisation by double refraction

ne > no

ve < vo

Velocity or Refractive index is the same along the OPTIC AXIS for o-ray and e-ray.

ne < no

ve > vo

Page 25: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

QuartzPositive crystal

Sphere

Spheroid

Wave surface is the locus of all points reached by the ray at a given instant

Velocity ellipsoid

ne > no

ve < vo

Page 26: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Sphere

Spheroid

ne > no

ve < vo

QuartzPositive crystal

Page 27: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Sphere

Spheroid

ne > no

ve < vo

QuartzPositive crystal

Page 28: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Calcite Negative crystal

Sphere

Spheroid

ne < no

ve > vo

Page 29: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Sphere

Spheroid

ne < no

ve > vo

Calcite Negative crystal

Page 30: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Sphere

Spheroidne < no

ve > vo

Calcite Negative crystal

Page 31: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Biaxial

Page 32: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Huygens’construction

Page 33: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Calcite ne < no

ve > vo

Page 34: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Special cuts of uniaxial crystalOptic axis normal to the surface of incidence

No double refraction

Page 35: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Optic axis parallel to the surface of incidence

No double refraction

Page 36: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Oblique IncidenceOptic axis parallel to the surface of incidence, normal to the plane of incidence

Page 37: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Nicol prism

Calcite

Canada balsamn = 1.55

no = 1.6584ne = 1.4864

Page 38: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Rochon prism

Page 39: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation
Page 40: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Wollaston prism

Page 41: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Elliptical and circular polarisation

Plane polarised

Circularly polarised

Etc.

Page 42: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Production of elliptically polarised light

O

E A O =

E =

Page 43: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Retarders

Quarter wave, Half wave and Full wave

Page 44: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

GLASS

Page 45: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Quartz

Page 46: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Quartz

Half wave plate

Page 47: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Variable retarder

Babinet Compensatoris a

. . . . . .

. . . . . . . . . . . . . .. . . . . . . . .

C

))((2

21 eoo

nndd

Page 48: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Interference of polarised light

Fresnel-Arago laws

1. Two coherent rays polarised at right angles do not interfere

2. Two parallel coherent polarised rays will interfere in the same way as will ordinary light

Page 49: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Optically active medium

Specific rotation= 21.72 Deg/mmfor Sodium lines

Rotation of the plane of vibration & Rotatary dispersionDextrorotatary or right handed mediumLevorotatary or left handed medium

Page 50: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Sugar, Glucose and Fructose

Sugar (Sucrose or Cane sugar)

Glucose-D ( Dextrose or Grape sugar)

Fructose (Levulose or Fruit sugar)

Specific rotation

52.7

66.47

- 92

o

o

o

Page 51: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Specific rotation is defined as the observed rotation of light of wavelength 589 nm (the d line of a

sodium lamp) passing through 10 cm of a 1 g ml-1 solution of a sample.

Rotation in liquids

One can find out the density of substance in solution

[ρ] = 10 θ / ldSpecific rotation,

θ = angle of rotationl = Length of the liquid column in cmd = density in gm/cm3

Page 52: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Fresnel’s explanation of rotation

Page 53: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation
Page 54: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Induced Optical Effects

Isotropic medium can be made optically anisotropic applying

1. Stress : Photoelastic Effect2. Magnetic field : Faraday Effect3. Electric field : Kerr effect

Page 55: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Faraday effect

B

d

=Verdet cosntant

0.00001-0.01 min/Gauss-cm

Page 56: 1 Polarization 1. Polarisation XY – Plane: Plane of polarisation

Kerr effect

An isotropic medium becomes birefringent by an application of electric field.

It behaves like an uniaxial crystal with optic axis in the direction of applied field.

K = Kerr Constant