OPTICS PRESENTATION
“ POLARIZATION ”
Presented to :
Sir (Dr) Abdur Rehman
Presented By :
➢ Ali zain BSPHY-22-05
➢ Muhammad Farid Shahid BSPHY-22-01
➢ Muhammad Shahid Adeel BSPHY-22-36
➢ Muhammad Usman BSPHY-22-12
➢ Safdar Bashir BSPHY-22-41
INTRODUCTION TO POLARIZATION
Definition Polarization :-
▪ It is a phenomenon explaining Wave Nature of Light .
▪ Causes the vibrations to occur in Single Phase only .
▪ It proves that light consist of Transverse Wave Nature .
Unpolarized Light :-
▪ Consists of waves with planes of vibrations Equally Distributed in all directions along
direction of propagation .
▪ Symmetrical about ray direction .
▪ Produced by Conventional light Sources .
Polarized Light :-
▪ Consists of waves with planes of vibrations in Single Phase perpendicular to
the direction of propagation .
▪ Asymmetrical about ray direction .
▪ Obtained from unpolarized light via Polarizer .
Demonstration of Unpolarized and Polarized Light :-
TYPES OF POLARIZATION
➢Three types of Polarization :-
▪ Plane Polarized Light (Linear Polarization)
▪ Circular Polarization
▪ Elliptical Polarization
Linear Polarization :-
▪ Electric field vector of Light is limited to Single Plane only along the direction
of propagation .
Circular Polarization :-
▪ It occurs when two Orthogonal Electric Field Vector Components are
𝜋
of same magnitude and are out of phase by exactly 90° or .
2
▪ I can rotate in one of two possible directions :
1) Right –handed Circular Polarization
2) Left-handed Circular Polarization
Elliptical Polarization :-
▪ It occurs hen the two of Electric Field Vector are of not equal
magnitude and differ in phase by an arbitrary angle .
Demonstration of Types of Polarization :-
INTRODUCTION TO BIOT POLARISCOPE
DEFINITION :-
▪ A simple instrument for Producing and Detecting Plane Polarized
light by Reflection .
CONSTRUCTION :-
▪ It consists of two glass plates P1 and P2 .
▪ To avoid total Internal reflection and absorb refracted light both
plates are painted back on their sides .
▪ P1 plate is called Polarizer and P2 plate is called Analyzer .
DIAGRAM :-
PRINCIPLE :-
▪ Monochromatic light ray falls on plate P1 at polarizing angle and reflected vertically upward along BC
and incident on other plate P2 which is also held parallel to P1 , also at polarizing angle and is reflected
along CD .
▪ When plate P2 is gradually rotated about BC as axis the angle of incidence on plate P2 is still same .
▪ Intensity of reflected ray CD decreases and becomes zero for a rotation of 90° of plate P2 , on further
rotation of P2 intensity of CD goes maximum at 180° and then decreases till 270° where it again
becomes zero and then again maximum at 360° .
▪ As the beam is incident on P1 at polarizing angle , the reflected beam BC is completely plane polarized
with its vibration perpendicular to the plane of incidence .
▪ When P2 is parallel to P1 the vibrations of BC are perpendicular to the plane of incidence , therefore ray
BC is completely reflected as ray CD and intensity is maximum , when P2 is perpendicular to P1
vibrations of BC are parallel to the plane of incidence with respect to the plate
P2 therefore no light is reflected .
BREWSTER’S LAW
STATEMENT :-
“ When an unpolarized light of known wavelength is incident
on a transparent substance surface , it experiences maximum
polarization at the angle of incidence whose tangent is the
refractive index of the substance for the wavelength . ”
MATHEMATICAL RPERESENTATION :-
𝝁 = 𝐭𝐚𝐧 𝒊𝑷
Where , 𝝁 is the refractive index of medium and 𝒊𝑷 is the angle of polarization or
Brewster’s angle .
RELATION BETWEEN CRITICAL ANGLE AND BREWSTER’S ANGLE :-
𝟏
𝜽𝑪 = 𝐬𝐢𝐧−𝟏
𝐭𝐚𝐧 𝜽𝑩
DIAGRA M :-
IMPORTANT KEYPOINTS :-
▪ Gives a relationship of light waves at maximum polarization of light .
▪ According to this law , plain polarized rays vanishes completely on
different glasses at a particular angle .
▪ Brewster’s Angle is angle of incidence where the ray of light having plain
polarization is transmitted through dielectric surface i.e. transparent without
any reflection .
▪ The unpolarized light at this angle is transmitted , the light is reflected from the surface .
APPLICATIONS :-
▪ Polarized Sunglasses
▪ Polarizing Lens for Photography
MALUS LAW
STATEMENT :-
“ The intensity of plane – polarized light that passes through any
analyzer varies as the square of the cosine of the angle between plane
of polarizer and the transmission axis of the analyzer . ”
MATHEMATICAL REPRESENTATION :-
I = 𝐈𝐨 𝐜𝐨𝐬 𝟐 𝜽
where , 𝐈𝐨 is the intensity of incident polarized light and 𝜽 is the angle between direction of transmission
of analyzer and polarizer .
VALUE OF INTENSITY BEAM TRANSMITTED FROM POLARIZING SHEET :-
𝟏
I = 𝐈𝐎 𝐜𝐨𝐬 𝟐 𝜽 = 𝐈𝐎
𝟐
DIAGRAM :-
IMPORTANT KEYPOINTS :-
▪ It provides a relationship using light intensity between polarizer and analyzer .
▪ Malus conducted an experiment in which he demonstrated that natural incident
light could be polarized when reflected by a glass surface .
▪ Used calcite crystal in his experiment .
▪ Concluded a result that natual light consisted of s and p polarization which are
perpendicular to each other .
APPLICATIONS :-
▪ Helps to understand the relation between Optics and Electromagnetism .
▪ Demonstrates the transverse nature of light .
