ELECTROMAGNETIC WAVES ( English )

Definition
Electromagnetic waves is one of the classified based on its medium wave, electromagnetic wave itself included into waves that can propagate through a medium or vacuum (without medium). Electric and magnetic fields are always perpendicular, and both are perpendicular to the direction of propagation. Hence, electromagnetic waves including transverse wave, and can experience polarization (direction of vibration absorption part). Discovered electromagnetic waves by Heinrich Hertz. Magnetic field varies with time can generate (induce) electric fields in the form of electrical current. This phenomenon is known as electromagnetic induction phenomenon. The concept of electromagnetic induction discovered by Michael Faraday experimentally and formulated in full by Joseph Henry. Electromagnetic induction law itself became known as the Faraday-Henry Law.

Michael Faraday, the discoverer of electromagnetic induction

The basic wave equation
Basic equations of electromagnetic waves, namely:
c = λf
(Quick creepage = wavelength x frequency)
With c = 3.0 × 〖10〗 ^ 8 m / s.
Form of electromagnetic waves
When we see the propagation of electric and magnetic fields in one direction only, then the electric field image (red) and changes in magnetic field (blue) which produces an electromagnetic wave is shown in Figure 1.1. As said above that, electric field and magnetic field is always perpendicular to each other, and both are perpendicular to the direction of propagation. Hence, electromagnetic waves including transverse wave, and can experience polarization (direction of vibration absorption part).

Figure 1.1 Forms of electromagnetic waves. The electric field is always perpendicular to the magnetic field and either perpendicular to the direction of propagation.

Properties - properties of electromagnetic waves
Changes in electric and magnetic fields occur at the same time, so that the two fields have a maximum and minimum prices at the same time and at the same place.
Direction of electric field and magnetic field perpendicular and keduannya perpendicular to the direction of propagation.
Like the waves in general, experiencing a wave of reflection, refraction, interference, and diffraction. And experience because it includes a transverse wave polarization.
Rapid propagation of electromagnetic waves depends only on the properties of electric and magnetic medium yaang taken.
Not distorted in an electric field or magnetic field because the electromagnetic waves have no electric charge.
The spectrum of electromagnetic waves

The spectrum of electromagnetic waves consist of various types of electromagnetic waves which are distinguished by frequency (f) or wavelength (λ), ie ranging from radio waves to gamma rays. Consider the following figure,

Figure 1.2 The spectrum of electromagnetic waves
Radio waves
Based on the wide-frequency, radio waves are divided into 5 groups: Low Frequency (LF), Medium Frequency (MF), High Frequency (HF), Very High Frequency (VHF) and Ultra High Frequency (UHF) (see table 1.1). MF and HF radio waves can reach distant places of the earth's surface because these waves can be reflected by the ionosphere is the upper atmosphere. LF waves is absorbed by the ionosphere, while the VHF and UHF waves can penetrate the ionosphere, which can be used to kominikasi remotely using satellites. For more details, see figure 1.3.

Width Frequency Wavelength Used In
Low Frequency (LF)
30 kHz - 300 kHz 1500 m long wave radio and remote communication
Medium Frequency (MF)
300 kHz - 3 MHz to 300 m of local medium wave and long-distance radio
High Frequency (HF)
3 MHz - 30 MHz 30 m short-wave radio and amateur radio communications and
Very High Frequency (VHF)
30 MHz - 300 MHz 3 m FM Radio, police, and emergency services
Ultrahigh Frequency (UHF)
300 MHz - 3 GHz 30 cm TV (channels 4, 5)
Super High Frequency (SHF)
> 3GHz 3 cm radar, satellite communications, telephone, and TV channels

Figure 1.3 VHF & UHF so it can pass through the ionosphere to the satellite, MF & HF can not pass through the ionosphere, but reflected, while the LF is absorbed by the ionosphere.

In the radio transmitter modulators, merged electric vibrations vibration sound by radio frequency carrier waves so as to produce the modulated radio waves. If processed in it is the amplitude, then the wave dihasilakn are AM (Amplitude Modulation). Meanwhile, if processed in it is the frequency, then the resulting wave is FM (Frequency Modulation). Here's an example of the radio image Figure 1.4.

Figure 1.4 One example of the benefits of an electronic device that uses electromagnetic waves.

Microwaves
Microwave (micro waves) dalah radio waves with the highest frequency (Super High Frequency (SHF)). Microwaves are generated by special electronic pelaratan, for example in the klystron tube. Microwaves one used in microwave heating.

Figure 1.5 How the microwaves in a microwave heater.

Radar (Radio Detection and ranging)
Radar (Radio Detection and ranging), which means finding and determine the distance of an object using microwaves (frequency ± 〖10〗 ^ 10 Hz). Plane distance from the radio determined by the equation:
c = cΔt / 2
Divisor 2 arises because the microwave pulse must travel a distance s away-home. (See Figure 1.6)

Figure 1.6 Illustration of how the radar picture.

Infrared rays
Infrared light has a frequency range 〖10〗 ^ 11 - 〖10〗 ^ 14 Hz. These rays generated by vibrations of electrons in a molecule because it is heated. These rays are used to: physical therapy (physical therapy), infrared photography for the purposes of diagnosing the disease.

Figure 1.7 Infrared Photography

Visible Light
Visible light is electromagnetic radiation waves that can be detected by the human eye. Based on the sequence of the smallest frequency, visible light has a light Red, Orange, Yellow, Green, Blue, Indigo and Purple.

Figure 1.8 Visible light

Ultraviolet light
These waves are generated by atoms and molecules in an electric flame. UV rays are needed in the assimilation of plants, and can kill germs skin diseases. And the sun is a major source of ultraviolet (UV) on the surface of the earth. Figure 1.9 there is a way of UV reached the earth.

Figure 1.9 UV rays enter the earth.

X - ray
X - rays produced by electrons - electrons in the inner electron shells of atoms, or electron emission occurs due to the pace of metal mashing. X - rays can be used to photograph the position of the fracture.

Figure 1.10 x-rays can be used to photograph of fracture