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.
