The Theory of Electromagnetic wave

Definition of Electromagnetic Waves

The man who first tested the hypothesis Maxwall the electromagnetic wave is Heinrich Hertz, in 1887 (Foster, 2004). The experiments carried out by Hertz provides a definition of electromagnetic waves. Supriyono (2006) states that "electromagnetic waves consist of a magnetic field and electric field which changes periodically and simultaneously, with a vibration direction perpendicular to one another, and each field is perpendicular to the direction of wave propagation".

Attributes of Electromagnetic Waves

From several experiments that have been done, Hertz succeeded in measuring that radio frequency electromagnetic wave radiation (100 MHz) has a velocity that is raised in accordance with the value predicted by Maxwell. In addition, Hertz experiment also shows the properties of light waves, namely monitoring, refraction, interference, diffraction and polarization. Thus, the hypothesis of the Maxwell electromagnetic waves have been proven true through Hertz experiment. From this description, can be written properties of electromagnetic waves are:

a. Can propagate in a vacuum,

b. Is a transverse wave,

c. Can be polarized,

d. Can undergo reflection (reflection),

e. Can undergo refraction (refraction),

f. Be susceptible to interference,

g. Can undergo bending or scattering (diffraction),

h. Propagates in the direction lurus.Berdasarkan calculations have been done Maxwell, the electromagnetic wave velocity diruang vacuum is 3 x 108 m / s which is equal to the speed of light measured (Supriyono, 2006).

Foster (2004) states that the wavelength of visible light has a range of between 400 nm to 750 nm. Anonymous (2009) states that the frequency of visible light can be calculated by the following equation:

c = f x λ

Description:

c = speed of light (3 x 108),

f = frequency (Hz)

λ = wavelength (m).

Based on these equations, we can determine the frequency of visible light is worth between 4 x 7.5 x 1014 Hz to 1014 Hz.

Definition Spectrum Electromagnetic Waves

Electromagnetic wave spectrum is the arrangement of all forms of electromagnetic waves by wavelength and frequency. The lowest frequency or wavelength of the radio waves and the biggest is the highest frequency or the smallest waves are gamma rays.

Various Kinds of Electromagnetic Waves Spectrum

Electromagnetic waves consist of an assortment of different wave frequency and wavelength. However, its speed in a vacuum is the same (Foster, 2004). Sequence spectrum electromagnetic wave frequencies are sorted from smallest to largest is a frequency) radio waves, b) television waves, c) mokro wave (radar), d) infrared light, e) of visible light, f) ultraviolet light, g) rays X, and h) gamma rays.

a. Radio Wave

Frequency radio wavelengths stretched from a few kilometers to 0.3 meters. Frequency radio waves stretched around a few hertz and energy photons moving from about 0 to 10 eV. Anonymous (2009a) stated that based on the width of the frequency, radio waves can be divided into Low Frequency (LF), Medium Frequency (MF), High Frequency (HF), Very High Frequency (VHG), Ultra High Frequency (UHF) and Super High Frequency (SHF).

Foster (2004) states "frequency modulation as an information carrier is superior compared with amplitude modulation (AM) because the AM transmitter will sound emergency due to the events of electricity and magnetism in the air that can interfere with the amplitude of the wave".

b. Television waves

Television wave frequencies slightly higher than radio waves. These waves propagate straight and can not be reflected by the layers of the Earth's atmosphere so as to catch the telecast, needed a station connecting, for example station Jakarta, then in Bandung area needed a station connector that is located on a mountain top Maras while the eastern part of Indonesia requires in the form of a satellite link station (Foster, 2004).

c. Microwave

Supriyono, (2006) states that the wavelength of the micro stretched from 0.3 meters up to 0,001 meters with a frequency of 109 hertz stretched to 3 x 1011 hertz. Microwave area marked as UHF means ultra high frequency radio frequency relatife against. These waves are generated by special electronic equipment, for example in the klystron tube.

d. Infrared

Supriyono, (2006) stated that extends from the infrared wavelength of 7.8 x 10-3 meters to 10-7 meters with inframereh frequency range of 3 x 4 x 1011 hertz to 1014 hertz. Lala (2008) states infrared rays produced by electrons in molecules vibrate because the object is heated. Thus, any hot object memancarka infrared light with light emitted depends on the temperature and color of objects.

e. Light Looks

Visible light is an electromagnetic wave spectrum that can be seen by the human eye. Supriyono (2006) states that the wavelength of light stretched from 7.8 x 10-7 meters (red) to 3.8 x 10-7 meters (purple) with light frequency of 4 x 8 x 1014 hertz to 1014 hertz. The light produced by the atoms and molecules caused because they said there internal changes in the movement of electrons.

i. Ultraviolet rays

The sun is ultraviolet light which has a high ultraviolet radiation. Supriyono (2006) states that the wavelength of ultraviolet light stretching of 3.8 x 10-7 meter up to 6 x 10-10 meters with a frequency range of 8 x 1014 hertz to about 3 x 1017 hertz. Ultraviolet light produced by the atoms and molecules are electrically charged.

j. X-ray

X-rays have wavelengths ranging from 10-11 meters to 10-9 meters with a frequency range of 1016 hertz to 1020 hertz so that these rays have a strong enough penetrating power that can penetrate thick books, thick wood, and even 1 cm thick aliminium plate (Anonymous, 2009c). Anonymous (2009b) states that "the X-rays produced by electrons residing in the inner electron shells of atoms, or that occur due to the electron beam with great speed metal mashing". Supriyono (2006) concluded that X-rays have the properties, namely:

a. Vines according to the straight,

b. Can discolor film plates,

c. Can ionise the gas as it has a high energy,

d. Can penetrate thin metal,

e. Can not be deflected by an electric field and a magnetic field,

f. Cathode rays emitted when mashing metal,

g. Can eject electrons from the photo ditumbukkan metal surface.

h. Gamma rays

Gamma rays have a shelf waves of 10-10 meters to 10-12 meters with a frequency of 1018 to 1020 (Supriyono, 2006). Gamma rays are electromagnetic waves which have the greatest frequency and form of radioactive nuclei issued certain. This wave has a great energy that can penetrate metal and concrete.

Electromagnetic Waves Role in Life

Electromagnetic waves widely used in life on earth. The utilization in various fields, namely medicine, industry, astronomy, art, and science of physics. The benefits derived from the utilization of these electromagnetic waves. However, electromagnetic waves can also be a negative impact that can interfere with life on earth.

The radio waves used by many people in the field of communication that is used as a communication tool and carrier information from one place to another. One of them is used in broadcast television systems, radio and electronic devices that generate electrical oscillations.

The role of electronic means of communication may be adversely affected. It is located on the electromagnetic waves generated. Taufik (2009) mentions that the electromagnetic waves generated by the electronic device can cause mental disability because of the brain's neurons we were disturbed by the wave. In addition, if there is contact when the local gas station pumping gas that can be dangerous because the electromagnetic waves can trigger an explosion of a gas station. Therefore, we must be careful when in derah pump.

Supriyono (2006) states that the waves emitted from the radio station transmitter is reflected by a layer of Earth's atmosphere. The atmospheric layer containing electrically charged particles-particles, namely the ionosphere so that it can reach places on earth that were located far from the transmitter. Radio waves can penetrate the ionosphere at a photon energy of about 108 Hz. Waves that carry information forwarded by the ionosphere. Information in the form of sound waves carried by supporters as the frequency changes and is referred to as frequency modulation (FM).

Microwaves are used in the analysis of the structure of atoms and molecules, and are also used in radar (radio detecting and ranging). Mokro waves are also used in intercontinental communication with the help of satellites so that even long-distance communication obstructed by mountains can be done. Satellite position must be considered because the satellite's position affects the communication links worldwide. Merry (2009) states that "The microwave oven uses microwaves in the ISM frequency band around 2.45 GHz. .... Heating with microwaves has the advantage that the heating more evenly because not transfer the heat from the outside but generate heat from inside the material ".

Infrared rays can not be detected by the naked eye but can still be felt because of the heat energy generated. Every day people can sense infrared light coming from the sun that are beneficial to the human body. Lala (2008) states that 80% of sunlight is the infrared light because this light wave length range (4 to 1000 microns).

Infrared light is widely used in industry, in health or medicine, astronomy, and in the study of molecular structure. Foster (2004) stated that in the medical field infrared light can be used to reduce pain in arthritis and warms the surface of the skin. Infrared rays are not a lot of scattered by particles so that in the field of astronomy using plates film that is sensitive to infrared light, the shooting of the plane surface of the earth by satellites can be done. Infrared light can be used to study the structure of molecules by using infrared spectroscopy.

Visible light or visible light can help our eyesight. With the visible light, our eyes can see objects around us and can be distinguished assorted colors.

Ultraviolet light can be used to kill the microorganisms, by ultraviolet radiation is absorbed to destroy microorganisms such as the reaction proceeds because ionosasi and dissociation of molecules. These rays can change the molecules of plant sterols from provitamin D into vitamin D which is useful for the growth of the human body (Supriyono, 2006). Foster (2004) states ultraviolet rays can also be used to determine the elements in a material with spectroscopic techniques because this ray frequency range between 1015 hertz to 1016 hertz.

In addition to providing the advantages, ultraviolet rays also cause a great loss of life. Ultraviolet rays contained in the sun can be absorbed by the ozone layer in the atmosphere. If the ozone layer in the atmosphere hollow, it can increase the ultraviolet rays that reach the earth's surface and can damage skin tissue in humans (Foster, 2004). Ultraviolet rays carry more energy than other light waves. Because this is the ultraviolet waves can enter and burn human skin so the skin becomes sensitive to the sun's ultraviolet rays. It may cause cancer of the skin (Anonymous, 2009b).

X-rays are also called X-ray. In the medical field these rays used to photograph the broken bones, kidney stones, lung, and other body parts. In modern times, Supriyono (2006) states that the X-ray used in surgery so that doctors can know which part should be dissected. In the field of light industry is used to find defects and wrap weld metal because this light can be able to penetrate the metal. In the field of art, X-rays are used to see the inside of the statue which is not visible from the outside. In the science of physics, X-rays are used to study the diffraction patterns in the atomic structure of a material that can be used to determine the structure of the material.

Gamma rays are very harmful to humans because it can kill living cells especially the gamma rays with a high level of energy released by nuclear reactions such as a nuclear bomb.

Foster (2009) stated that the Ground Penetrating Radar is a geophysical method using electromagnetic techniques designed to detect objects buried in the ground and evaluated into the object.