CHAPTER I

INTRODUCTION1.1 BackgroundElectromagnetic wave is a wave phenomenon generated by the interaction of changes in the electric field and magnetic field changes that occur simultaneously. As for some of the properties of electromagnetic waves is (1) a transverse wave, (2) an incident involving reflection, refraction, interference, diffraction, and polarization, (3) is not affected by the electric field and magnetic field because it does not have a charge. One is the nature of an incident electromagnetic wave polarization. Polarization occurs only in transverse waves alone, while the longitudinal wave polarization does not occur as the sound waves do not experience polarization.One example is the electromagnetic waves of light, so as the light is an electromagnetic wave, the direction of vibration of light waves perpendicular to the direction of propagation. One proof of light as an electromagnetic wave is experiencing symptoms of light polarization, which absorbed most of the intensity of an incident beam of light by a particular material. Polarized light can occur due to a variety of events such as events of reflection, refraction, twin bias, selective absorption and scattering.In everyday life, we often encounter is actually the polarization phenomena, such as clouds in the blue sky. It is caused due to scattering of sunlight by the Earth's atmosphere. If the earth did not have atmosphere, the sky would appear dark (black), except when we look directly at the sun. But the fact is, the earth has an atmosphere, so on a sunny day, the sky will appear blue. This occurs because the blue light sky blue color dissipated. In addition, there are also many other events that are the sources of the polarization. For more details about the polarization of electromagnetic waves, it will be discussed in more detail in this paper, be it of the understanding, the types of polarization, and polarization sources.CHAPTER IIDISCUSSION2.1 The definition Polarisasi

Light is a transversal waves, where E and B field are propagate each others.

Gambar 1. The relation between E and B field in electromagnetic waves (Yasa, 2001)Light waves can appears in polarization incident. Light polaritation or optic polarization are absorbed half of lights. Polarizations is one of light characteristic, i.e the light are move in oscillation with certain direction. A light can be said polarizated if that light are propagate with certain direction. The direction in polarizated field electromagnetic wave are taken as a electric field vector.

Gambar 2. Oscillation field electromagnetic waves polarizated (Anonim, 2008)In discussion about electromagnetic waves about equation of electromagnetic waves before, we get E = Eo ei(k.z - (.t)and B = Bo ei(k.z - (.t)for dielectric medium and equation E = Eo e-(.z ei((.z - (.t) dan B =

e-(.z ei((.z - (.t + () for conductive medium . in discussion before, the amplitude of electromagnetc waves Eo and Bo assumed constant both of this medium in equation , Bo = (k/()x Eo And both of this medium are in perpendicular field with wave propagate, then the characteristics of this waves are depend with amplitude in field that it pass through.Because this vectors from electric field and magnetic field from electromagnetic wave are always perpendicular with wave propagate so there are degree of freedom of movement from electromagnetic field vectors. Polarization from electromagnetic field are manifestation from movement degree of freedom from electromagnetic field vectors. In this casus, assumed that electromagnetic wave propagate to z-positive and transversal field from waves in xy field. This statement conclude that wave amplitude from x and y axis, wave amplitude in xy field. So Eo located in xy field, so electric fieldcan draw in x and y axis.

(1.1)

because Eox and Eoy; both is complex number so both of this units can appeard it

(1.2a)

(1.2b)

So E can expressed by equation E = Eo e-(.z ei((.z - (.t) and become;

(

)ei(k.z - (.t) (1.3)

to make simple this equation, we can assume that k is real, then with take the real part from electromagnetic field components from electromagnetic waves is

)(1.4a)

)(1.4b)

then this statement are depend on the amplitude relative (E1,E2) dan fase (). Bila -E1 ( Ex ( E1 dan - E2 ( Ey ( E2 ,so according 1.4 the electric field E are in maximum limit area like draw in picture below Gambar 3. From the picture are draw that the electric field is a fisis units of wave not are complex number

Gambar 3. Electric field component transversal field (Yasa, 2001)For certain different time as equation 1.4, vector components of electric field are change, then E also change as the change of its vector component. Vector figure E will make trajectory in xy area bounded by the value of E1 and E2. The trajectory can eliminated (k.z - (.t) from equation 1.4

(1.5a)

(1.5b)

Then from both of equation can determined and we get

(1.6a)

(1.6b)

With square each of equations (1.6a) dan (1.6b) and adding it, we get;

(1.7)

Equation 1.7 are the general equation from an ellipse. With this the electric field can be said in ellipse polarizated. The trajectory are draw in bellow

y

Gambar 4. Electric field are polarizated as ellipse (Yasa, 2001)Although polarization are determine for electric field, magnetic field are also polarizes. Magnetic field from electromagnetic wave will polarizes as ellipse in xy area because magnetic field are also perpendicular with electric field. So the equation are determined for electric field are belong to for magnetic field. Gambar 5. Polarization process using polarizator (Riyanto, 2006)Figure 5 show that light is not polarizes that fall in polarizator. In polarizator there is certain characteristics polarization that showed in parallel lines. That polarizator just transmited the components of wave that the its electric vectors are propagate parallel to this direction and absorb the components of electric vectors that propagate perpendicular to this direction. The light out is light that has been polarizes by area. The direction of this polarizes are resulted in made process with put the molecules long chain in a plastic plat which flexible and then make long the plat so the molecules are parallel each others.Gambar 6. Sebuah Rentetan Gelombang E adalah Ekivalen dengan Dua Rentetan Gelombang Komponen Ey dan Ex (Riyanto, 2006)In figure 6, polarizes plat are located in area and the its propagate are into the picture. E arrows emit the propagate field from wave that has choose randomly and fall into the plat, two components vectors are Ex (E Sin ) dan Ey (E Cos ) can change E , one is paralles each other and the other one are perpendicular toward polarizes direction

Gambar 7.Cahaya yang tak Terpolarisasi tidak Ditransmisikan oleh Plat-Plat Pemolarisasi yang Bersilangan The second polarization plat (Analisator) are located like figure 7. If the second plat is rotated toward the propagate direction, so the state of second polarizes are separated 180O, where the light intensity that transmited almost equal to zero. This states is where the direction of plat polarization I and II are perpendicular each othersIf the amplitude of polarizes wave fall in second plat is Em, so the light amplitude is Em Cos , where is angle between polarization direction from plat I and plat II. With increase the light intensity are equal to square from amplitude, so we can see that the intensity that transmitted I change with according equation

(1.8)

Where Im is maximum value of intensity that transmitted. The maximum value occur where if the direction if polarization is = 0 atau 18002.2 Kind of Polarization

The value from main axis of ellipse and the direction toward the axis depend on the amplitude E1 and E2 and relative phase from both component. Because equations 1.7 just depend from absolute value from different ((, so with concern the amplitude and different phase equation 1.7 can determine some shapes of polarization. Kasus =0

According to the equation 1.7 it could be.

(1.9)

Equation (1.9) expressed that straight line equation located a long the diagonal xy area. Like figure

Gambar 8. Trajectory vector of electric field from polarizes wave with different phase is zero1. ((= (The equation will be

(2.0)

According equation (2.0) will give the result like straight line. In this casus same with the first casus, electromagnetic wave are polarizes linear, but between Ex with Ey always have different sign. Positive sign for =0 and negative sign for ((= (. The trajectory can be showed

Gambar 8. Trajectory vector of electric field from polarizes wave with different phase is 2. ((=

For polarization ((= , the equation will be

(2.1)

the figure is

Gambar 9. Ellips polarization with different phase ((=

In ellipse polarization like figure 9, appear casus where E1 = E2 = E0, so the equation (2.1) become the circle equation with radius E0.

(2.2)

According equation (2.2), polarization are called circle polarization.( =

(2.3)

And the different phase for Ex in PP =

(2.4)

So the equation become 2.4 Ex = E1 cos P dan Ey = E2 cos (P - ()(2.5)

For more understanding the equation 2.5 are draw in graphic that explain the fisis difeerent ( positip, negatip dan nol.

Gambar 10. Grafik E Sebagai Fungsi Dari PFrom equation (2.5), that related equation E with P. if ( ( 0 so Ex leave Ey, it means Ey reach maximum after Ex reach maximum, and Ey become zero after Ex become zero.

( (0

( ( 0

(a)

(b)

Gambar 11. a. Lintasan ellip berlawanan putaran jarum jamb. Lintasan ellip searah putaran jarum jam2.3 Sources of Polarization

As already introduced in the previous study, there are some events which are optical sources that generate polarization where the methods used to produce polarization in general produce linear polarization. Events that result in polarization optics including gas laser beam, the Zeeman effect, synchrotron radiation, absorption (absorption), event reflection and transmission, scattering, dichroism and double refraction (Yasa, 2001).

a. Polarization due to Gas Laser Beam

Gas laser which emits monochromatic light is very sharp and coherent which has a wavelength that is identified from the same frequency and have a constant phase difference. In addition, the laser gas emission can allow the polarization due to the angle of incidence of monochromatic light qualifies as Brewster angle.

b. Polarization due to the Zeeman Effect

Another source of polarization that can occur related to the Zeeman effect where a very sharp spectral lines placed in a magnetic field so that the fracture line or in other words the Zeeman effect is the separation of a wavelength to several wavelengths when applied magnetic field. Of the fractional line, each component of the spectral lines will be linear or circular polarized.

c. Polarization due Synchrotron Radiation

As a source of polarization can also be produced from synchrotron radiation where there is high-speed electrons into the magnetic field resulting form a circular path. Acceleration experienced by the electrons to emit light offending trajectories of electrons. Radiation emitted light is polarized light.

d. Polarization due to absorption (absorption)

To generate linearly polarized light can be used with Polaroid materials known.

Picture 12. Selective polarization scheme using Polaroid filters. Only light with parallel orientation of the polarization axis of the polaroid is forwarded Polaroid materials continuing to be light with a certain vibration direction and absorbs the others vibration direction of light. Transmitted light is light whose direction of vibration parallel to the polarization axis of the polaroid. Polaroid combines substances that have dichroism, which is where one of the selective absorption of polarized components are absorbed much more powerful than the other components, as shown in Figure 13

Picture 13. Polaroid combines substances having dichroism

As shown in Figure 14, A ray of natural light (unpolarized) to polarisator. Natural light is indicated by the vector-vector E are pointing in all directions (random) and perpendicular to the direction of propagation. Here the vertically polarized light that is only the electric field component E parallel to the transmission axis. Polarized light next to the analyzers.

Picture 14. Two Polaroid, first Polaroid called Polarisator the second is called analyzer with the transmission axis from an angle

In analyzers, all E components perpendicular to analyzer transmission axis is absorbed, only the component E parallel to the axis of the analyzer passed. So the strenght electric field analyzers forwarded to:

E2 = E cos ...(2.6)

If natural light is not polarized, which falls on the first Polaroid (polarisator) has intensity I0, the polarized light that passes through polarisator are:I1 = I0 .....(2.7)

Light with intensity I1 is then headed analyzers and will come out with the intensity becomes:

I2 = I1 cos2 = I0 cos2.......(2.8)

e. Polarization due to reflection (Reflection) and Transmission

Light reflected by a smooth surface will be partially polarized when the angle of incidence is not zero. These events are generally stronger in a dielectric boundary surface when the angle of incidence at or near the Brewster angle name.

Figure 15 shows the incident polarization by reflection and transmission of light at the boundary y. When the reflected beam forming and beam angle 90o transmission is not possible if the light reflected electric field lies in the plane coming (( polarization), but this light will be transmitted. Light by an oscillating electric field perpendicular to the plane coming (( polarization) can be reflected. Thus the Brewster angle can be determined as follows:

.....(2.9)

From Snellius can be:

......(3.0)

Cause and so, from equation (2.9) and equation (3.0) got:

......(3.1)

Picture 15. Polarization by reflection and transmission (Yasa, 2001)

with called Brewster angle. If the light comes not polarized, then the Brewster angle reflected light will experience ( polarization, while the transmission of only a small light just undergone polarization(, most them experienced ( polarization.

f. Polarization due to scattering

Light scattering can occur when a space occurs in the distribution of particles of irregular scattering centers. For example, dust particles in the air, which is much smaller than the wavelength of light, the particles in suspension kolloid, or gas molecules particles in the air. Basic mechanisms of the polarization of light from unpolarized incident light by scattering particles are similar to those described in polarization by reflection and transmission of light.

Picture 16. Polarization of incident light by scattering particles (Yasa, 2001)

Figure 16 shows that the scattered light 90o to the direction of incident will experience linear polarization with the electric field in the direction perpendicular to the plane of scattering, which is the field formed by the direction of the incident light with the direction of the scattered light. The scattering event occurs in the Earth's atmosphere. The blue color of the sky is caused by the scattering of short wavelength of blue light is much larger than the scattering of light red color. Blue light from the sky is partially polarized light with the electric field vector oscillates toward the right corner of the field containing the incident light and scattered light. At the point of view of 90o like picture 16 looks a complete polarization.

g. Polarization due to the double refraction

If the glass is passed on glass, the speed of light come out will equally in all directions. This is because the glass is homogeneous; refractive index has only one value. However, in certain crystalline materials such as calcite and quartz, speed of light in it is not uniform because of the material it has two values refractive index (birefringence).

Double refraction is a phenomenon that occurs in calcite crystals or others non cubic crystals as well as the plastics that stretched like slofen. Medium in which the speed of light equally in all directions is called isotropic medium while the medium in which the speed of light was not uniformly called anisotropic medium. When a light beam enters the medium anisotropic, light beam will be separated into two parts, namely the ordinary beam o (ordinary) and extraordinary beam (special beam) e (extraordinary). This looks like the following figure.

Picture 17. Beam of light entering the crystal of twin bias

From the figure above shows that the polarized rays with different direction and velocity. Ordinary ray o will satisfy Snell's law of refraction at the crystal surface. Instead, extraordinary ray e does not meet Snell's law of refraction. Difference between beams o and e rays in relation to Snell's law can be explained as follows.

(1) o pass beam inside the crystal with the same velocity vo for all direction. In other words, for this crystal sheaf has the same refractive index that is no.

(2) e beam pass in the crystal with the change ranging of velocity from vo to a certain value greater (vc). In other words, the index of refraction is defined as c / v ranging from no change to a smaller value nc.

2.4 Application of Polarization

1. LCD (Liquid Crystal Displays)

LCD terms appear frequently in the field of electronics. Liquid crystal can be translated as liquid crystals. This name is used because the solid and liquid properties are two different things. The molecules of solids dispersed regularly and keep its position, while the molecules of a liquid layout or irregular position so that it can move freely in any direction. In 1888 a botanist, Friedrich Reinitzer, find the phase between solid and liquid phases. This phase has the properties of solid and liquid together. Molecules such as solid objects, but can move freely like a liquid. Furthermore, this phase is called liquid crystals. Liquid crystalline phase is closer to the liquid phase due to the slight increase in temperature (heating) immediately turns into a liquid phase. This trait showed high sensitivity to temperature. Thus, liquid crystals are very sensitive to temperature changes. Nature is the basis for the use of liquid crystal technology. In addition to temperature, the liquid crystals are also very sensitive to electric current (potential difference). The principle of this kind is used in LCD technology. This is why the laptop screen sometimes looks different in the winter or when used in very hot weather.

Picture 18. Differences in molecular characteristics

Types of liquid crystals are used in the development of LCD technology is the nematic type (the molecules have a particular pattern in a particular direction). The simplest type is a Twisted Nematic (TN), which has a molecular structure naturally selected by 90o. This structure can be removed its twisted TN (untwist) by using an electric current.

Picture 19. Nematic Phase Picture 20. Twisted Nematic (TN) Ilustration

Figure 20 shows the TN liquid crystal (D) is placed between two electrodes (C and E) and still wrapped again with two glass panels (B and F) a thin layer on the outside given the polarizing film. Layer A is a film that can reflect light which able to penetrate the layers of wrapping LCD. Electrode C and E linked to the voltage as a current source. Panel B have different polarization 90o with panel F.Basic concept of how the LCD works is the wave physics and optics, especially on light as an electromagnetic wave, the light associated with color and vision, and the light polarization as a wave. LCD work by using Liquid Crystal which has been described earlier. LCD do not produce light, but only modify the light from a source. This is what makes LCD energy-saving. Light modifications made by LCD are the polarization of light as an electromagnetic wave.Some equipment that utilize technology such as computer screens (flat screen), calculators, and digital watches.

Picture 21. LCD Layer compotition diagram

Computer screen

calculator

digital watchPicture 22. Some equiptment used LCD

2. Polarization glasses

Right now there are a few impressions on television that 3D or three dimensional image. To watch 3D display, we have to use special glasses.

If you note that 3D glasses are sold in the stores left lenses of different colors with the right lens color. Lens for the right eye is red, while the lens for the left eye is blue.

When the glasses are used, red shadows seen by the blue lens and blue shadows seen by the red lens. Thus, each eye sees a different way. Both of these colors are red and blue was chosen because it is related to the wavelength of light. In a 3D display, the red color will make objects invisible in the back. The depth dimension is obtained by playing the two colors are in the process of making the film.

Picture 23 (a) Red and Blue Lens Glases (b) polarizes glases

Viewing 3D movie with two color glasses turned out image color to be less interesting. This is because the light vibrates in all directions. Polarization will cause light to vibrate only in one direction. In order polarized, the light was passed through light polarisator. Polarisator / filter is mounted on eyeglass lenses. So in order the left eye and right eye see slightly different things, right eye lens mounted filter that will withstand vertical light waves, while the left eye lens fitted with a filter that will withstand the horizontal light waves. By using these glasses, the color image into a beautiful 3D display.

CHAPTER III

CLOSING3.1 ConclusionBerdasarkan pembahasan, maka dapat disimpulkan sebagai berikut.

1. The polarization of light or optical polarization is partially absorbing vibration direction of light. The general equation for the electric field is polarized

and the intensity which transmited after polarizied is .

2. Type of polarization consist of 3, which are:

a) Linier Polarization.

b) Ellip Polarization.

c) Circular Polarization.3. Events that result in polarization optics including; beam laser gas, Zeeman effect, synchrotron radiation, incident absorption, reflection and transmission, scattering, dichroisme and double refraction.4. The application of the concept of polarization in daily life can be seen on the LCD and polarization glasses.

Lebih terpolarisasi (

Terpolarisasi (

Cahaya tak terpolarisasi

Terpolarisasi (

x

y

lebih terpolarisasi (

Polarisasi (

90

(B

Ey

Ex

Ey

Ex

Ey

Ex

B

E

k

Ex

E2

Ey

-E1

E1

x

E

E

Ey

Ex

EMBED Equation.3E

y

x

y

E2

-E2

Ex

-E1

E1

x

E

Ey

1Polarisasi Kelompok II

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