Electromagnetic radiation, also known as electromagnetic radiation, is by the same phase oscillation and mutually perpendicular to the electric field and magnetic field in space in the form of waves to transfer energy and momentum, the direction of its propagation is perpendicular to the plane formed by the electric field and magnetic field.
Electromagnetic radiation carriers for photons, do not need to rely on the medium of propagation, the speed of propagation in a vacuum for the speed of light. Electromagnetic radiation can be categorized according to frequency, from low frequency to high frequency, mainly including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.
The human eye can receive electromagnetic radiation, the wavelength of about 380 to 780nm between, called visible light. As long as its own temperature is greater than absolute zero of the object, can emit electromagnetic radiation, and the world does not exist in the temperature equal to or below absolute zero of the object. Therefore, all objects in people's neighborhood are emitting electromagnetic radiation at all times. Nonetheless, only electromagnetic waves that are within the frequency range of visible light can be seen by people's naked eyes.
Electromagnetic energy in the form of wave propagation to a distance without returning to the source of the wave, called electromagnetic radiation, will cause in pollution. Electromagnetic wave pollution can be divided into natural electromagnetic pollution and man-made electromagnetic pollution two categories.
Natural electromagnetic pollution mainly refers to cosmic rays, atmospheric lightning, the sun and the earth's thermal radiation and other electromagnetic interference, is caused by certain natural phenomena. Man-made electromagnetic pollution refers to the production of electronic and electrical equipment and a variety of life of electromagnetic radiation generated by the work of electronic products, mainly divided into eight categories:
①Nuclear electromagnetic pulse;
②Radio transmitting equipment;
③Industrial, scientific and medical radio-frequency equipment;
④Electricity, transportation and industrial facilities;
⑤Electrostatic discharge type of equipment;
6 lighting and household appliances;
7 office automation equipment;
8 electronic information products;
The frequency range of man-made electromagnetic radiation is wide, the intensity is greater than that of the natural environment, electromagnetic pollution sources, and the living environment with the human race is more closely related to the relationship between the electromagnetic environment has become the main factor in the electromagnetic pollution.
According to different frequencies, man-made electromagnetic pollution sources are divided into industrial frequency sources and radio frequency sources. Industrial frequency sources (frequency of tens to hundreds of hertz) in the high-power transmission lines produced by electromagnetic pollution, including some discharge-type industrial frequency sources: radio frequency sources, including radio equipment and large-scale radio frequency production equipment. Radio frequency sources of frequency width (frequency of 0.1-3000MHz), the impact of a large range of...?
Types and sources of man-made electromagnetic pollution sources
Discharge sources: corona discharge, arc discharge, glow discharge, spark discharge, etc.
Induction sources of industrial frequency: high-power power transmission lines, electrical equipment, electric traction systems, electromagnetic stoves, electric blankets, etc.
Radio-frequency sources of radiation: radio transmitters, mobile base stations, radar, microwave heating equipment, high frequency heating equipment, cell phones, walkie-talkies, radio frequency therapy machines, computers, home theater equipment, etc.
The pathway of electromagnetic pollution is divided into space radiation, wire propagation and compound pollution.
Space radiation refers to when electronic and electrical equipment work, through its surrounding space constantly radiating electromagnetic energy. This radiation is a field source as the center, in the form of electromagnetic induction from the field source within a wavelength radius of the instrumentation, electronic equipment and human body. The other is to electromagnetic radiation from the field source of a wavelength outside the region of the sensitive components and the human body.
Wire propagation is the electromagnetic energy of radio frequency equipment through the power line or signal line to act on other electronic equipment, the formation of interference mode.
And compound pollution refers to the simultaneous existence of space radiation and wire propagation of electromagnetic pollution. The use of electromagnetic shielding materials can effectively solve this problem