1. POLARIZATION OF LIGHT & ITS APPLICATION
RAMACHANDRA COLLEGE OF ENGINEERING, ELURU
K LOKESWARA RAO
Asst professor

2. PRESENTATION LAYOUT Concept of Polarization Types of Polarization
Methods of achieving Polarization

3. Electric field E and magnetic field B are:
ORDINARY LIGHT
Electromagnetic wave
Electric field E and magnetic field B are:
Perpendicular to each other
In phase
Also perpendicular to the direction of
propagation

4. Electric field vector Magnetic field vector
Em wave

5. ORDINARY LIGHT Unpolarized Light
In a beam of light, if the oscillations of E vectors are in all directions in a plane perpendicular to the direction of propagation, then the light is called unpolarized light.

6. POLARIZATION Transforming unpolarized light into polarized light
Restriction of electric field vector E in a particular
plane so that vibration occurs in a single plane
Characteristic of transverse wave

7. Why only electric field vector is considered in polarization and not magnetic field vector?
Maxwell’s Equation
E=c × B
c is velocity of light(c=3 × 108 m/s),very large value
E>>>B i.e. EM wave is predominantly an electric
wave
To change any characteristics of EM wave, including
polarization, E should be affected

8. .
Polarization

9. Plane of vibration Plane of polarization
A plane including the direction of light propagation
and the direction of electric field
Plane of polarization
The plane perpendicular to the plane of vibration

10. Linear Polarization Circular Polarization 3. Elliptical Polarization
TYPES OF POLARIZATION
Linear Polarization
Circular Polarization
3. Elliptical Polarization

11. LINEAR POLARIZATION Plane polarized wave
The electric field of light is confined to a single plane along the propagation direction in linear polarization.

12. Resultant wave is linear in vertical plane
Resultant wave is linear in 450 plane

13. Superposition of plane polarized wave
Two plane polarized waves are added according to
the rules of vector addition
Results in a linear, elliptical or circular polarized wave
depending on the amplitude and the phase shift
between two waves

14. CIRCULAR POLARIZATION
The electric field of light has two linear components that are perpendicular to each other and have identical amplitudes, but the phase difference is π ⁄ 2 (or) 900. The electric field that occurs will propagate in a circular motion.
May be right circularly polarized(clockwise) or
left circularly polarized(counterclockwise)

15. Blue wave is resultant circular polarized wave.
Blue wave is resultant circular polarized wave

16. .
Superposition of oppositely polarized waves results in to plane polarized wave

17. ELLIPTICAL POLARIZATION
The electric field of light propagates along an elliptical path. The two linear components do not have the same amplitude and phase difference.
Consists of two perpendicular waves of unequal amplitude that differ in phase by 900
The tip of the resultant electric field vector describes an ellipse in any fixed plane intersecting and normal to the direction of propagation
Circular and linear polarization: special cases of elliptical polarization

18. Blue wave is resultant elliptical polarized wave
Green wave is resultant elliptical polarized wave

20. METHODS OF ACHIEVING POLARIZATION
Reflection
Scattering
Dichroism or Selective absorption
Birefringence or Double refraction

21. POLARIZATION BY REFLECTION
When the light is allowed to be incident on a non metallic surfaces like snow, glass at particular angle, the reflected beam is completely plane polarized.
Incident angle is such that angle between reflected
and refracted ray is 900
Such incident angle is known as polarizing angle or
Brewster’s angle
Reflected ray is completely linearly polarized and vibrations are perpendicular to the plane of incidence.

23. BREWSTER’S LAW When light is incident at polarizing angle:
The tangent of polarizing angle=Refractive index of
material
i.e, tan θ = µ
For Sapphire, µ=1.77
So, θ=tan-1(1.77)=
If the angle of incidence is not exactly the Brewster’s angle the reflected ray will only be partially polarized

24. Malus law
It helps us to study the relation of the intensity of light and the polarizer-analyzer. 
It states that the intensity of plane-polarized light that passes through an analyzer varies directly with the square of the cosine of the angle between the plane of the polarizer and the transmission axes of the analyzer.

25. The intensity of the incident light on the analyzer ‘I0’ is directly proportional to the square of the amplitude of the electric vector ‘E0’.
I ∞ E02
The intensity ‘I’ of light transmitted by the analyzer is,
I ∝ (E0  x cosθ)2
Hence,
I / I0 = (E0 x cosθ)2/E02 = cos2θ
I = I0 x cos2θ
Therefore,  I ∝ cos2θ