The document discusses several methods of polarizing light, including polarization by refraction, polarization by scattering, polarization by transmission, and polarization by reflection. Polarization by scattering occurs when light strikes atoms in a material, causing the electrons in the atoms to vibrate and produce secondary electromagnetic waves that are partially polarized. Various everyday situations demonstrate polarization effects, such as polarized sunglasses blocking horizontally polarized glare on surfaces like roads and water. Polarization is also used in 3D movies, where two polarized images are projected and viewed through polarized lenses to give the perception of depth.

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3. Polarization
Polarization is a property of waves that can
oscillate with more than one orientation.
Electromagnetic waves such as light exhibit
polarization, as do some other types of wave,
such as gravitational waves.
Sound waves in a gas or liquid do not exhibit
polarization, since the oscillation is always in
the direction the wave travels.

4. Electromagnetic Wave
Light is an electromagnetic wave.
It consists of vibrations of electric field
and magnetic field.
The electric field and magnetic field are
perpendicular to each other and in phase.
EM wave is a transverse wave.
The speed of EM wave is 3 x 108 ms-1.

5. Polarized Light
single
Polarized Light: Vibrations lie on one
plane only.
Unpolarized Light: Superposition of many
beams, in the same direction of propagation, but
each with random polarization.
Unpolarized
Polarized
E
E

6. Polarization by Transmission
Polarization by Reflection
Polarization by Refraction
Polarization by Scattering
Methods of Polarizing Light
It is possible to transform unpolarized light into polarized
light. Polarized light waves are light waves in which the
vibrations occur in a single plane. The process of
transforming unpolarized light into polarized light is
known as polarization. There are a variety of methods of
polarizing light. The four methods discussed on this page
are:

7. Polarization by Refraction
Polarization by Scattering
When light strikes the atoms of a material, it will often set the
electrons of those atoms into vibration. The vibrating electrons
then produce their own electromagnetic wave that is radiated
outward in all directions. These vibrating electrons produce
another electromagnetic wave. This scattered light is partially
polarized.

8. Polarization In Everyday Situations
This photograph should be compared with the one above.
In this photo, the reflected glare that was seen on the
water's surface (previous photo) has been removed by the
use of a Polaroid filter. It is much easier to see the sidewalk
below the water surface.

9. Action of Polaroid Sunglass
Unwanted glares are
usually horizontally
polarized light
Light reflected from surfaces like a flat road or smooth
water is generally horizontally polarized. This horizontally
polarized light is blocked by the vertically oriented
polarizers in the lenses.
Vertically Polarized Light
from Objects

10. Polarization is often implemented in the
production and viewing of 3D films. When
watching a 3D movie, there are actually
two images being projected onto the
screen at once. The two images were
filmed with two separate cameras from
two slightly offset locations. These two
images are projected onto the screen
through Polaroid filters. The molecules of
one of the filters is aligned vertically, the
other is aligned horizontally. The audience
is given 3D glasses that have one lens
aligned horizontally and the other aligned
vertically. Thus, one eye sees one image
and the other eye sees the other image.
The brain receives both signals and
perceives depth on a flat screen.
Polarization in 3D Movies

11. The sky is blue because . . .
• The tiny particles in the atmosphere (dust, clumps of air
molecules, microscopic water droplets) are better at
scattering shorter wavelength blue light than the longer
wavelength red light.
• As sunlight passes through the atmosphere, the
scattered blue light give the atmosphere an overall blue
glow.

12. The sunset is red because . . .
• At sunrise and sunset, sunlight enters our atmosphere at
a shallow angle and travels a long distance before
reaching our eyes.
• During this long passage, most of the blue light is
scattered away and virtually all that we see coming to us
from the sun is its red and orange wavelengths.