Q: What is called electromagnetic radiation?
A: energy in the form of electromagnetic waves through space propagation phenomenon.
Q: electromagnetic radiation pollution sources of those types?
A: 1, radio and television transmitting equipment, the main sectors of radio and television broadcasting stations and relay stations around the world.
2, communications radar and navigation transmitting equipment communications, including short-wave transmitters, microwave communication stations, terrestrial satellite communication stations, mobile communication stations.
3, industrial, scientific research, medical high-frequency equipment.
4, electromagnetic radiation interference in transportation systems, including: electrified railroads, light rail and electrified railways, rail trams, trackless trams, etc..
5, electromagnetic radiation of the power system, high-voltage transmission lines, including overhead transmission lines and underground cables, substations, including power plants and transformer power stations.
6, household appliances electromagnetic radiation, including computers, monitors, televisions, microwave ovens, induction cookers, wireless phones, cell phones and so on.
Q: electromagnetic radiation affects the human body mechanism is mainly what?
A: Now most people know that the hospital X-ray can not be photographed too often, the reason is that frequent X-ray radiation may have a cumulative effect on health hazards. Similarly, the human body to receive electromagnetic radiation is too strong, too long or too close, may also cause harm, its role in the human body is mainly thermal, non-thermal and cumulative effects.
(1) thermal effect more than 70% of the human body is water, water molecules by electromagnetic radiation friction with each other, causing the body to warm up, thus affecting the normal work of the body organs.
Domestic and international research has confirmed that the role of electromagnetic radiation on the human body is mainly thermal effect, the harm is mainly in the radio frequency electromagnetic field. Substation radiation belongs to industrial frequency electromagnetic field, not radio frequency electromagnetic field. When the field strength of radio frequency electromagnetic field reaches a certain value, in order to have an effect on the human body. Under the action of radio frequency, the human body absorbs electromagnetic radiation energy, its energy will be converted into heat. Only when more than the ability to regulate body temperature, only to make the temperature balance dysfunction, caused by the body temperature rise, thus producing physiological dysfunction and pathological changes and other biological effects.
(2) non-thermal effects of human organs and tissues are weak electromagnetic field, they are stable and orderly, once the interference of external electromagnetic field, in a state of equilibrium of the weak electromagnetic field is about to be destroyed, the human body will also suffer damage.
(3) cumulative effect Thermal and non-thermal effects on the human body after the role of the human body has not yet had time to repair the damage to the human body before (usually referred to as the human body's tolerance - internal resistance), and then again subjected to electromagnetic radiation, the extent of the damage will occur cumulatively, and in the long term, will become permanently sick.
Q: What is the role of electromagnetic radiation?
A: Electromagnetic radiation can be described as magical, in many places can see its figure. Specific applications are:
(1) medical applications: microwave physiotherapy blood, treatment of tumors, etc.
Treatment of tumors in the antenna or the radiator can control the temperature in only kill cancer cells within a very narrow temperature range. Electromagnetic radiation thermotherapy uses electromagnetic energy to warm up local tissues, improve blood circulation, promote metabolism and achieve the purpose of treatment.
(2) Transmission of information: communication, radio, television, etc.
Communication mainly includes microwave communication and long and short wave communication, such as cellular phone and satellite phone. There is also the use of long and short-wave communication, such as walkie-talkies. Broadcasting involves turning sound into electric current and then spreading it out in the form of waves through a transmitting antenna.
(3) target detection: radar, navigation, remote sensing, etc.
Radar works is the transmitter to detect the target sends a pulse wave, the pulse wave encountered in the detection of the target can be reflected back, it can be measured between the reflected wave and the transmitter of the time interval, so as to know the detection of the target and the radar is located at the distance.
(4) induction heating: induction furnace, high-frequency quenching, high-frequency melting, high-frequency welding, high-frequency cutting, etc.
The use of high-frequency electromagnetic field energy in the medium and long-wave bands to make the conductor or the semiconductor itself heats up, to achieve the purpose of thermal processing.
(5) medium heating: microwave ovens, microwave dryers, plastic heaters, etc.
The non-conductor placed in a strong electromagnetic field, its positively and negatively charged molecules or atoms in the alternating electromagnetic field, under the action of the frequency of the electric field oscillation, "friction" caused by the heat, to achieve the purpose of processing.
(6) military applications: electronic warfare, electromagnetic weapons, etc.
such as the Gulf War, the United States first identified the Iraqi army to use the signal frequency, and then use the same frequency to send out signals with stronger power, resulting in Iraq
Q: What is the working principle of electromagnetic shielding device? What are the main electromagnetic radiation protection products?
Electromagnetic shielding device is generally a closed shell made of metal materials. When the electromagnetic field to the metal shell, part of the surface of the metal shell is reflected, part of the shell is absorbed in the interior, so that the intensity of the electromagnetic field through the shell will be greatly attenuated. The effect of electromagnetic shielding and electromagnetic wave frequency, shell thickness and shielding material properties and so on. Generally speaking, the higher the frequency, the thicker the shell, the better the conductivity of the material, the greater the shielding effect.
Protective clothing is made according to the principle of shielding or absorption. Protective eyewear is used to protect the operator's glasses from injury, the requirements for protective eyewear are: translucency should be high enough not to affect the line of sight; shielding effect should be good (in principle, should ensure that the shielding of the field strength control in the national standard limits below); light weight, mirror start flexible. The basic material of protective glasses is metal mesh or metal film.
Q: daily life how to protect against electromagnetic radiation?
A: The following points need to be noted:
Computer Electromagnetic waves occur in the front and back of the computer (referring to conventional CRT computers). Computer screen will radiate anions, the operation should be at least 30 centimeters away from at least 30 centimeters above the moment of power on the electromagnetic radiation is the largest, should be avoided, on the machine after the best every hour to take a break from activities for a while.
Television When watching television, it is best to be more than 3 meters away from the television, immediately after turning off the television away from the television.
Microwave oven When using a microwave oven, be careful to stay at least 0.5 meters away from the oven, keep your eyes away from the door, and don't stand in front of the oven for a long time. After removing food from the oven, let it sit for a few minutes before eating.
The electric blanket is equivalent to an electromagnetic field, even if you turn off the switch, will still disturb the body's natural electric field, pregnant women, children, the elderly, the greatest damage, should be used with caution.
In addition, attention should also be paid to the home of electrical appliances placed too centralized, so that they are exposed to excessive doses of radiation in the dangerous period. Such as radios, televisions, refrigerators and other electrical appliances, it is more inappropriate to focus placed in the bedroom. All kinds of household appliances, office equipment, cell phones, etc. should try to avoid prolonged operation, and at the same time try to avoid the simultaneous activation of a variety of household appliances. Television, computers and other electrical appliances need to be used for a long time, it should be noted that at least once every hour to leave. In the daily diet, should eat more carrots, tomatoes, kelp, lean meat, animal liver and other foods rich in vitamin A, C and protein, to strengthen the body's ability to resist electromagnetic radiation.
Q: What is the frequency of common sources of electromagnetic radiation?
A: High-voltage power equipment: industrial frequency 50Hz.
GSM mobile communication base station: 900/1800MHz.
CDMA communication: 825-880MHz.
PHS (PHS): 1915-1900 MHz.
Medium wave broadcasting: 535-1605KHz.
Shortwave broadcasting: part of the band within 4-19 MHz.
FM (sound) broadcasting: 88-108 MHz.
Television: five bands 50-92, 168-223, 471-566, 607-958 MHz.
Home microwave ovens: 2450 MHz, industrial microwave ovens: 915, 2450 MHz.
High-frequency induction heating equipment (such as melting furnaces, quenching furnaces, etc.): working frequency of several hundred kHz.
High-frequency dielectric heating equipment: working frequency of a few MHz to dozens of MHz.
High-frequency media heating equipment: working frequency of a few MHz to dozens of MHz.
There are five bands of ultra-short wave (USFW): 50-92, 168-223, 471-566, 607-958 MHz. p>
Ultra-short wave electrotherapy machine: 40.68 MHz.
Q: electromagnetic radiation frequency band how to categorize
A: Electromagnetic fields across a wide range of frequencies, from the industrial frequency (50Hz/60Hz) to the microwave section, and the role of communication varies greatly, and thus the consequences of the impact on human health varies greatly.
Usually, the spectrum of electromagnetic waves can be roughly divided into industrial frequency (50Hz/60Hz), radio frequency or high frequency (103 to 108 Hz) and microwave (>109 Hz) three frequency bands.
Name of band
Corresponding band
Abbreviated name
Frequency range
Low
Frequency
Very low frequency
Very low frequency
10,000-meter wave (very long wave)
VCF
30 Hz to 30 KHz
Low frequency
Kilometer Wave (Long Wave)
CF
30KHz~300KHz
Intermediate Frequency
Hundred Meter Wave (Medium Wave)
MF
300KHz~3000KHz
RF
Frequency
High Frequency
Decimeter Wave (Short Wave)
< p>HF3MHz~30MHz
VHF
30MHz~300MHz
Micro
Wave
Ultra High Frequency
Decimeter Wave
UHF
300MHz~3GHz
Micro
Wave
Universal High Frequency
Decimeter Wave
UHF
300MHz~ 3GHz
UHF
Centimeter wave
SHF
3GHz~30GHz
Extremely High Frequency
Millimeter wave, sub-millimeter wave
EHF
30GHz~300GHz 300GHz~3000GHz
Note: Conversion : 1 KHz=1000Hz 1MHz=1000 KHz 1GHz=1000MHz
Q: How is electromagnetic radiation generated?
A: We know that there are generally two kinds of forces interacting between objects: one is generated through the direct contact of the object, called the contact force. Such as friction, collision, push and pull forces. The other kind can occur without contact, and such forces are called field forces. Examples are electricity, magnetism, gravity, etc.
There exists a special substance around an electric charge called electric field. It is not the same as solid, liquid or gaseous matter, it cannot be seen or touched, it is a special form of matter. The interaction between two charges is not a direct action of the charges, but an action that occurs by the electric field of one charge on the other. In other words, there is always electric force acting in the space around the charges. Therefore, we call the space in which electric forces are present an electric field. A magnetic field is a certain space with magnetic force created by an electric current around the conductor through which it passes.
Electric and magnetic fields are interconnected, interacting and co-existing at the same time. Due to the existence of an alternating electric field, it will produce an alternating magnetic field around it; the magnetic field changes, and will produce a new electric field around it. They move in directions perpendicular to each other and to themselves. The sum of this alternating electric and magnetic fields is what we call the electromagnetic field.
This changing electric and magnetic fields are produced alternately, from far and near, and continuously radiate energy into the surrounding space as they propagate through space at a certain speed, and this radiated energy is called an electromagnetic wave, and the phenomenon of this energy in the form of an electromagnetic wave emitted into space from a source is called electromagnetic radiation.
Q: What is meant by noise?
A: Any object that does mechanical vibration will propagate the vibration in all directions through the surrounding elastic medium (e.g., gases, liquids, and solids), forming mechanical waves. Under certain conditions, mechanical waves can cause the human ear hearing or other receptor response, which is sound. To produce sound, there must be a mechanical vibration of the object (i.e., the source of sound), but also have the ability to propagate the sound of the medium, that is, the sound field. In addition to air, gases, liquids and solids can also be used as a medium to propagate sound. Because of the different sound transmission medium, noise propagation can be divided into air noise, solid noise and water noise.
Two, environmental management
Q: electromagnetic radiation pollution prevention and control of relevant legal provisions, standards, what are the main?
A: For the environmental management of electromagnetic radiation, the state has a more systematic regulations and standards, which is the national implementation of radiation environmental management of the legal basis and evaluation of construction projects accompanied by electromagnetic radiation scientific standards. Mainly:
"Chinese People's *** and State Environmental Impact Assessment Law" (Chinese People's *** and State Presidential Decree No. 77);
"Measures for the Management of Electromagnetic Radiation Environmental Protection" (State Environmental Protection Administration Decree No. 18);
"Environmental Protection Categorization and Management Directory of Construction Projects" (State Environmental Protection Administration Decree No. 14);
< p>Provisions on Protection against Electromagnetic Radiation GB8702-88;Technical Specification for Evaluation of the Environmental Impact of Electromagnetic Radiation on 500kV Ultra-High Voltage Power Transmission and Substation Projects HJ/T24-1998.
Q: What are the main legal provisions and standards related to the prevention and control of noise pollution?
A: For the noise environment management, the state has a more systematic regulations and standards, which is the legal basis for the implementation of the state radiation environment management and evaluation of the scientific standards accompanied by noise construction projects. Mainly:
"Industrial noise standards" GB12348-1990
"Standard for environmental noise in urban areas" GB3096-93.
Q: What is the national limit of exposure to electromagnetic radiation?
A: In order to protect the environment, safeguard public health, and promote the development of legitimate practices accompanied by electromagnetic radiation, the State Environmental Protection Administration issued the "Regulations on the Protection against Electromagnetic Radiation" (GB 8702-88) on the exposure limits of electromagnetic radiation are specified in detail, of which the standard limit of the public's most sensitive range of 30-3000 MHz is 0.4W/m2, which is four times more stringent than the Western and international standards are four times more stringent.
The specific standards of "Regulations on Protection against Electromagnetic Radiation" are as follows:
Occupational Exposure During the working period of 8 hours a day, the Specific Absorption Rate (SAR) of the whole body averaged over any consecutive 6-minute period is less than 0.1W/kg.
Public Exposure During the 24-hour period of a day, the SAR of the whole body averaged over any consecutive 6-minute period is less than 0.02W/kg.
Public Exposure The public can be exposed to radiation of up to 30-3000 MHz.
Q: What is the standard for evaluating the environmental impact of electromagnetic radiation in power transmission and transformation projects?
A: The state has made detailed regulations on the environmental impact assessment of power transmission and transformation projects. 500kV ultra-high-voltage power transmission and substation projects electromagnetic radiation environmental impact assessment technical specifications" (HJ/T24-1998) applies to 500kV ultra-high-voltage power transmission and substation projects electromagnetic radiation environmental impact assessment, can also be referred to this specification is applied to the evaluation of the electromagnetic radiation environmental impact of the 110kV, 220kV and 330kV transmission and substation projects; approval of the above projects and the management of the present is also Reference to the implementation of the standard.
There is no national standard for the limit value of industrial frequency electric field and magnetic field strength of high-voltage power transmission and transformation facilities. In order to facilitate the evaluation, according to the research results of China's relevant units, power transmission line design regulations and reference to the limits of various countries, it is recommended that 4kV/m (kV/m) be used as the evaluation standard of the industrial frequency electric field in the residential area for the time being, and it is recommended that the International Radiation Protection Association (IRPA) should apply the limit value of industrial frequency of 0.1mT (milliTesla), i.e., 100 microTesla, for the whole day's radiation to the public, as the evaluation standard of the magnetic induction strength. When the corresponding national standard is released, its prescribed limit will prevail.
Q: What is the national limit for exposure to electromagnetic radiation?
A: In order to protect the environment, safeguard public health, and promote the development of legitimate practices accompanied by electromagnetic radiation, the State Environmental Protection Administration issued the "Regulations on Protection against Electromagnetic Radiation" (GB 8702-88) on the electromagnetic radiation exposure limits are specified in detail, of which 30-3000 MHz, the most sensitive range of the public within the standard limit of 0.4W/m2, which is four times more stringent than the Western and international standards, which is four times stricter than the Western and international standards.
This post is reprinted! /blog/static/277680902007317115438653/