Electromagnetic Radiation

by electromagnetics.info

Electromagnetic Radiation covers a range of wavelengths or frequencies but having the following properties:

Gamma Radiation (wavelength of 10-10 and 10-4 m)
Normally produced by the transitions within the excited nucleus of an atom and usually occurs as the result of some previous radioactive emission. It may be detected by photographic plates or a radiation detector such as a Geiger tube or scintillation counter.

X-Rays (wavelength of 10-11 and 10-9 m)
X-rays are produced by the most energetic energy changes of atomic electrons. X-rays are a form of ionizing radiation and the shorter wavelengths are highly penetrating. They can be detected by photographic film or with a fluorescent screen or by the ionization they produce in a geiger counter.

Ultraviolet Radiation (wavelength of 4x10-9 and 4x10-7 m)
Ultraviolet radiation is subdivided into three categories:

It is produced by fairly large changes in the electrons of an atom and it may occur in heavy or light elements. The Sun produces a large amount of ultraviolet radiation, which is mostly absorbed by the ozone layer on its way to Earth.

Visible light (wavelength of 4x10-7 (red) and 7x10-7 m) (violet)
This is the part of the electromagnetic spectrum to which the human eye is sensitive
The full spectrum, Red - Orange - Yellow - Green - Blue - Indigo - Violet, can often be seen in rainbows or when white light is passed through a prism. Visible light is produced by black body radiation from very hot objects such as stars and bulb filaments. The wavelenght of the light emitted depend on the nature of the atom and this is an important tool in chemical analysis.

Infrared Radiation (wavelength of 7x10-7 and 10-6 m)
The natural vibration frequency of atoms and molecules and the rotational frequencies of some gaseous molecules fall in the infrared region. Discovered in 1800 by William Herschel.

Microwaves (wavelength of 10-3 and 0.03 m)
Produced by specially designed electronic valves. High power microwave sets each use a magnetron valve which can radiate kilowatts of power. Radar waves are microwaves produced by magnetron valves.

Radio Waves (wavelength of about 1mm and over).
Produced by oscillating electric charge. Radio waves can be generates by oscillating currents in electric circuits and feeding this current into a wire or pattern of wires called an aerial or antenna. The oscillating charges in the aerial set up an oscillating electromagnetic field which spreads out into space as an electromagnetic wave. Another aerial can detect the wave, with either the electric or magnetic field producing a current in the aerial. A resonant circuit can be used to separate currents of different frequencies so that the receiving circuit can be tuned. Raiod waves can be subdivided into the following: