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When it comes to "radiation", everyone will immediately think of common electrical appliances in life - TV, computer, microwave oven, refrigerator, mobile phone... That's right, they do have radiation. But do you really know enough about the radiation in life?
"China Mobile Science and Technology Association" recently released a popular science video about radiation, which introduced: Anything in this world, whether it is TV computer or cats and dogs, has radiation. Including the sun, which we are most familiar with, there is also radiation, which emits electromagnetic waves and particle flows into the universe every moment. Although the earth has only received 1/2.2 billion of solar radiation, it is the main source of earth's atmospheric movement and light energy and heat. While absorbing solar radiation, the earth also radiates heat outward day and night. Therefore, "radiation" itself is a neutral word. Only when the intensity of electromagnetic radiation exceeds a certain standard will negative effects occur, harming the human body and causing different lesions in the human body. This part of radiation that exceeds the standard electromagnetic field intensity is called " electromagnetic radiation pollution ". There are three common radiations in
, namely electromagnetic radiation, solar radiation and thermal radiation .
electromagnetic radiation is also known as electromagnetic waves. Common electromagnetic radiation sources include radar systems, televisions, mobile phones and broadcast transmission systems, radio frequency induction and medium heating equipment, radio frequency and microwave medical equipment, various electrical processing equipment, communication transmission platform stations, satellite earth communication stations, large power stations, power transmission and transformation equipment, high-voltage and ultra-high voltage transmission lines, subway trains and electrical trains, etc., which can all generate electromagnetic radiation.
Solar radiation refers to the electromagnetic waves and particle flows emitted by the sun into the universe. The solar radiation energy received by the earth is only 1/2.2 billion of the total radiation energy emitted by the sun into the universe, but it is the main source of energy for the movement of the earth's atmosphere.
Heat radiation is a way for objects to transmit heat energy outward in the form of electromagnetic radiation. All objects in nature, as long as the temperature is above absolute zero (about -273.15 degrees Celsius), will constantly transmit heat to the outside in the form of electromagnetic waves and particles.
Image source: China Popular Science Expo official website
In 2014, my country integrated and revised the "Regulations on Electromagnetic Radiation Protection" and "Environmental Electromagnetic Wave Hygiene Standards", issued the "Electromagnetic Environment Control Limits" (GB8702-2014), and officially implemented it on January 1, 2015. According to this standard, the power density of the communication frequency band should be less than 40 microwatts/ square centimeters , while the US standard is 600 microwatts/cm2, which is 15 times the difference between the two. Professionals said that considering that base station signals will have superimposed levels, the standard implemented by mobile communication base stations is one-fifth of the national standard when building them, that is, less than 8 microwatts/square centimeter. What is the concept of the standard value of
? Taking hair dryer as an example, its power is generally above 1,000 watts. Because it is very close to the human body during use, its actual radiation can reach 100 microwatts/square centimeter. National standards are formulated based on long-term contact. No matter how long the human body is exposed to the radiation field, it is safe and there is no radiation accumulation effect.
Therefore, "electromagnetic radiation" and "electromagnetic radiation pollution" are two concepts. As mentioned above, any charged body has electromagnetic radiation, and the intensity of electromagnetic radiation exceeds the national standard will have a negative effect. Therefore, only radiation exceeding the standard electromagnetic field intensity is electromagnetic radiation pollution, and it is also a focus of people's prevention.
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Author: Jesse
Editor: Zhao Dina
Review: Gong Zimo
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