Plane waves reflection refraction and polarization contains the maximum description of the content

1. Electro
magnetic theory
Plane waves reflection refraction and
polarization
joint effort by
Dinesh raj
Rohit

2. Consists of
Plane waves
 Properties
 Reflection
 Refraction
 Total internal reflection
 Polaraization
 Applications


3. Plane waves
A plane wave can be written as
follows:
Here A represent the E or B
fields, q=i,r,t and j=x,y,z
So this is a representation of the
waves that is valid in all three
cases, i.e. the incoming, the
reflected and the transmitted
Boundary conditions
wave
The most importent condition at the
boundary is the existence of
continuity
This gives us that the tangential
component of the argument in the
wave-equations have to be equal,
i.e. the waves are in the plane of
A
q
j
q
j
Re a e
i(k
q
r wt )

4. Electromagnetic Waves





It consists of mutually perpendicular and oscillating electric
and magnetic fields. The fields always vary sinosidally.
Moreover, the fields vary with the same frequency and in
phase (in step) with each other.
The wave is  transverse wave, both electric and magnetic
a 
fields are oscillating perpendicular to the direction in which
E B
the wave travels. The cross product
always gives the
direction in which the wave travels.
Electromagnetic waves can travel through a vacuum or a
material substance.
All electromagnetic waves move through a vacuum at the same
speed, and the symbol c is used to denote its value. This
speed is called the speed of light in a vacuum and is:
The magnitudes of the fields at every instant and at any
point are related by

5. Properties of the Wave





Wavelength λ is the horizontal distance between any two
successive equivalent points on the wave.
Amplitude A is the highest point on the wave pattern.
Period T is the time required for the wave to travel a
distance of one wavelength. Unit is second.
Frequency f : f=1/T. The frequency is measured in cycles
per second or hertz (Hz).
Speed of wave is v=λ/T= λf

6. The Speed of Light



All electromagnetic waves travel through a vacuum at the same
speed, which is known as the speed of light c=3.00×108 m/s.
All electromagnetic waves travel through a material substance
with the speeds less than the speed of light in vacuum
c=3.00×108 m/s. The waves with different wave lengths may
have different speeds in a material substance.
In 1865, Maxwell determined theoretically that electromagnetic
waves propagate through a vacuum at a speed given by
c
1
0
3.00 10
0
8
(m/s)

7. Reflection and refraction
Why are we able to see ourselves
from mirror?
The incident ray, the reflected ray, and the normal to the
surface all lie in the same plane, and the angle of reflection
θr equals the angle of incidence θi:
r
i

8. Law of refraction
A refracted ray lies in the
plane of incidence and has an
angle θ2 of refraction that is
related to the angle of
incidence θ1 by:
the symbols n1 and n2
are
dimensionless constant, called the index of
refraction
ni
c
vi

9. Dispersion
The index of refraction encountered by light in any
medium except vacuum depends on the wavelength of
the light. The dependence of n on wavelength implies
that when a light beam consists of rays of different
wavelengths, the rays will be refracted at different
angles by a surface; that is, the light will be spread
out by the refraction. This spreading of light is called
chromatic dispersion,
•The index of refraction n in
the different materials is
different for the same wave
length of lights.
•The index of refraction n in
the same materials is different
for different wave length of

10. Total Internal Reflection
A phenomenon in which some of the light that is travelling
from
one medium into another is reflected & some is refracted
at the
 optical fibres
cladding between two media.
boundary(made of
another type of glass
with a lower refractive index)
core (made of glass)

11. Total Internal Reflection
we look at the phenomenon of total internal reflecection
which
is the opposite of the one just considered in that no
energy is transmitted across an
interface under appropriate conditions.

12. •Total internal reflection
•
• is the phenomenon in which incident light
is not refracted but is entirely reflected
back from the boundary. It happens only
when light travels from a medium in which
its speed is lower to a medium in which its
speed is higher.
The amount of reflection compared with the
amount of
refraction depends on the angle of incidence.

13. Polarization



Polarization is a characteristic of all transverse
waves.
Oscillation which take places in a transverse
wave in many different directions is said to be
unpolarized.
In an unpolarized transverse wave oscillations
may take place in any direction at right angles
to the direction in which the wave travels.
Direction of
propagation
of wave

14. Polarization of Electromagnetic
Waves


Any electromagnetic wave
consists of an electric field
component and a magnetic field
component.
The electric field component is
used to define the plane of
polarization because many
common electromagnetic-wave
detectors respond to the
electric forces on electrons in
materials, not the magnetic
forces.

15. Polaroid


A Polaroid filter transmits 80% or more of
the intensity of a wave that is polarized
parallel to a certain axis in the material,
called the polarizing axis.
Polaroid is made from long chain molecules
oriented with their axis perpendicular to
the polarizing axis; these molecules
preferentially absorb light that is polarized
along their length.
Polarizing axis

16. Polarization by Reflection
Unpolarized light can be polarized, either partially or completely,
by reflection.
The amount of polarization in the reflected beam depends on the
angle of incidence.


Brewster’s law

It is found that experimentally when the reflected ray is
perpendicular to the refracted ray, the reflected light
will be completely plane-polarized.
Incid
ent
ray
p
p
90
o
Reflected
n1
ray
n2
r

17. Polarizing angle (Brewster’s
angle)

The angle of incidence at which the
reflected light is completely plane-polarized
is called the polarizing angle (or Brewster’s
angle).
By Snell’s law,
Since
sin
p
r
n1 sin
sin( 90
and
90
r
o
p
)
cos
Then we get
tan
n 2 sin
p
n2
p
n1
p
r

18. Polarization by Scattering (1)

When a light wave passes through a gas,
it will be absorbed and then re-radiated
in a variety of directions. This process
is called scattering.
y
z
O
x
Unpolarized
sunlight
Polarization of Scattered Sunlight
z
Light scattered at right angles
is plane-polarized
y
O
E
Gas
molecule
x

19. Polarization by
Refraction

When an incident
unpolarized ray enters
some crystals it will be
split into two rays
called ordinary and
extraordinary rays,
which are planepolarized in directions
at right angles to each
other.

20. Double
Refraction

When light is refracted into two rays
each polarized with the vibration
directions oriented at right angles to
one another, and traveling at
different velocities. This phenomenon
is termed "double" or "bi" refraction.

21. 
Applications…..
Electric field of EM wave produces a
current in an antenna consisting of
straight wire or rods.
 Changing magnetic field
induces an emf and current
in a loop antenna.

22. THANK YOU !!
FOR YOUR
PATIENCE ..

23. Please follow d slides as follows
 Dinesh raj 1-6
 Kanishth
7-9
 Rohit
10-12
 Prashatnth 13-17
 Awadesh
18-21
