THE CONCEPT OF POLARIZATIONBY:

ROYA TAVANGAR & PARESH CHRISTIAN

TRANSVERSE WAVE

Transverse wave is a wave in which the direction of displacement is perpendicular to the direction of propagation, as a surface wave of water.

TRANSVERSE WAVE VS. LONGITUDINAL WAVE

In a longitudinal wave, the motion of the medium is parallel to the direction of the wave . This means that the particles move left and right which in turn makes the other particles start to oscillate. Sound waves are longitudinal waves. Transverse Waves a transverse wave is a wave in which the motion of the medium is a right angles to the direction of the wave.

TRANSVERSE WAVES

Transverse waves cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave.

LONGITUDINAL WAVES

In longitudinal waves the displacement of the medium is parallel to the propagation of the wave. A wave in a "slinky" is a good visualization. Sound waves in air are longitudinal waves.

YOUNG THOMAS LAWRENCE

YOUNG'S THEORY OF LIGHT

The law is, that 'whenever two portions of the same light arrive at the eye by different routes, either exactly or very nearly in the same direction, the light becomes most intense when the difference of the routes is any multiple of a certain length, and least intense in the intermediate state of the interfering portions; and this length is different for light of different colors.'

YOUNG'S THEORY OF LIGHT

Interference in young’s experiment was a crucial test for the wave theory of light, but it gave no clue to whether light waves are transverse or longitudinal

DANISH SCIENTIST ERASMUS BARTHOLINUSIN 1669, THE DANISH SCIENTIST ERASMUS BARTHOLINUS FOUND THAT WHEN HE DIRECTED A BEAM OF LIGHT INTO A CRYSTAL OF ICELAND SPAR (CALCITE), THE RAY WAS SPLIT INTO TWO BEAMS

POLARISATION

When light travels through space it vibrates in all planes. However, when light is passed through a polarising filter, the filter allows light waves through that are polarised in one plane. In other words, the only light that passes through a polarising filter is the light that was vibrating in the same plane as the polarising filter.

DISPLACEMENT OF LIGHT RAYS WITH PERPENDICULAR POLARIZATION THROUGH A BIREFRINGENT MATERIAL

A CALCITE CRYSTAL LAID UPON A GRAPH PAPER WITH BLUE LINES SHOWING THE DOUBLE REFRACTION

AFTER HORIZONTALLY POLARIZED LIGHTPASSES THROUGH THE ANALYZER, THELIGHT ENERGY IS REDUCED SIGNIFICANTLY

HORIZONTALLY & VERTICALLY POLARIZED

POLARIZATION CAN BE ACHIEVED FOUR WAYS

The first is by double refraction The second is by reflection The third way is through scattering The fourth method of polarizing is

to use a polarizing filter

DOUBLE REFRACTION THE PROPERTY OFCERTAIN CRYSTALS (E.G., CALCITE) TO SPLITAN INCIDENT BEAM OF LIGHT INTO TWO

POLARIZATION BY DOUBLE REFLECTION

POLARIZATION BY REFLECTION

when some absorption takes place at the point at which light is reflected off a smooth surface. Light waves reflected from a flat surface are partially polarized in the horizontal plane .Most glare comes from horizontal surfaces, such as a body of water, the hood of a car, or a paved road.

POLARIZATION BY REFLECTION

POLARIZATION BY REFLECTION

POLARIZATION BY REFLECTION

The polarizing filters in Polaroid sunglasses are for this reason arranged in the vertical plane, reducing glare by absorbing the horizontally polarized light reflected from horizontal surfaces.

POLARIZATION BY SCATTERING

Light from the Sun passes through our atmosphere and encounters small particles that scatter the light. Scattering causes the sky to appear blue, since the shorter wavelengths (shades of violet and blue) are scattered more than the longer wavelengths (shades of orange and red). This scattering also causes the light to be polarized.

POLARIZATION BY SCATTERING

You can demonstrate polarization by looking at the sky through a rotating polaroid sheet or through polarized sunglasses. The amount of polarization depends on the direction in which you look, being greatest at right angles to the direction of light from the Sun

http://www.youtube.com/watch?v=99cTTTbiFLA

POLARIZATION BY SCATTERING

POLARIZATION BY SCATTERING

Photographers use Polaroid filters to enhance photographs of

the sky and clouds. Since large stretches of the sky are significantly polarized, the polarizing

filter makes the clouds more prominent by reducing the glare

POLARIZING FILTER WITHOUT A POLARIZING FILTER WITH A POLARIZING FILTER

The fourth method of polarizing is to use a polarizing filter. Calcite, tourmaline, and other naturally occurring polarizing crystals are scarce and fragile, keeping polarization a laboratory curiosity until 1928.

CLOUD EFFECTS ARE ENHANCED WHEN WE ADD A POLARIZING FILTER TO THE CAMERA.

WITHOUT A FILTER WITH A POLARIZING FILTER

SUMMARY POLARIZATION OF LIGHT

Polarization of light can be achieved in the following ways: double refraction, reflection, scattering, and a polarizing filter.

• Polarization provided the proof that light is a transverse wave.

• Polaroid can be used to detect the presence of polarized light and the orientation of the plane of polarization.

• Scattering occurs when light from the Sun passes through our atmosphere and encounters small particles that scatter the light.

• Polarizing filters have many uses, including glare reduction, stress analysis, and photography.

• The optical activity of certain materials can be used to help identify some substances.