radiation

[fú shè]

Physical noun

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Radiation refers to the phenomenon that part of the electromagnetic energy emitted by the emission source (electromagnetic wave, etc electromagnetic wave Or particles (such as alpha particle 、 Beta particle And so on).

All objects in nature, as long as the temperature is Absolute temperature Zero degrees (approx -273.15 ℃ ）All of the above are in the form of electromagnetic waves and particles that constantly transmit heat to the outside. This way of transmitting energy is called thermal radiation 。

Radiated energy from radiation source Radiates straight outward in all directions. The energy emitted by objects through radiation is called radiant energy 。 Radiation press Roentgen /Hourly (R) calculation. An important feature of radiation is that it is "equivalent". No matter the temperature of the object (gas) is high or low, it will radiate outward. Object A can radiate to object B, and at the same time, object B can radiate to Party A. It is commonly used in ionizing radiation 。

Radiation itself is Neuter However, radiation from certain substances may cause harm.

Chinese name: radiation
Foreign name: Radiation
Essence: Physical noun

Pinyin: fú shè
Applied discipline: Telecommunications Nuclear Physics Radiomedicine
Communication mode: It is emitted from the heat source in a straight line all around

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five influence factor
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Radiation Overview

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According to the relationship with the field source, electromagnetic wave It can be divided into Communication mode It is a kind of radiation from the heat source along a straight line. Light radio waves The propagation of electromagnetic waves is also called radiation.

Radiation principle

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radiation It refers to energy in waves or Subatomic particle Type transfer of the move. Radiated energy from radiation source Radiates straight outward in all directions.

Radiation to electromagnetic wave And particles such as alpha particle 、 Beta particle And so on). radio waves And light waves are electromagnetic waves. Their propagation velocity Soon, the propagation speed in vacuum is the same as that of light wave (3 × 10 ^ 8 m/s).

Main types

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visible light It also belongs to radiation. Generally, it can be classified as ionizing radiation or Nonionizing radiation 。 The term is commonly used in ionizing radiation. Ionizing radiation has enough energy to ionize atoms or molecules, while non ionizing radiation does not. radiation Active substances It refers to the substance that can emit ionizing radiation. There are three main types of ionizing radiation: alpha, beta and gamma radiation (or radiation).

ionizing radiation

Radiation with high enough energy can ionize atoms. In general, ionization means that an electron is ionized from Electron shell To make an atomic band positive electricity 。 Because cells are made of atoms, Ionization Can cause cancer. A cell is made up of trillions of atoms. Induced by ionizing radiation cancer The probability of Radiation dose rate And radiation receiving organisms Inductivity 。 α. β, γ radiation and Neutron radiation Can be accelerated to ionize atoms with high enough energy.

Nonionizing radiation

Nonionizing radiation Its energy is weaker than that of ionizing radiation. Non ionizing radiation will not ionize matter, but will change the rotation, vibration or valence electron orbital state of molecules or atoms. The effect of non ionizing radiation on living tissues has not been studied for a long time. Different non ionizing radiation can produce different biological effects.

Common radiation

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solar radiation

Solar orientation Cosmic space Electromagnetic waves and particle streams emitted. The sun received by the earth Radiant energy Only the sun radiates into space Total radiation 1/2 billion of energy, but it is Earth's atmosphere The main energy source of sports. Reaching the upper boundary of the earth's atmosphere solar radiation Energy is called astronomical solar radiation. On Earth Average distance between the sun and the earth The total energy of the full spectrum of solar radiation received by the unit area of the upper boundary of the earth's atmosphere perpendicular to the solar rays in unit time is called Solar constant 。 Solar constant CUoM Is W/m2. Due to different observation methods and techniques, the solar constant values obtained are different. world meteorological organization (WMO) published the solar constant value of 1368 W/m2 in 1981. Upper bound of the earth's atmosphere Solar radiation spectrum More than 99% of them are between 0.15 and 4.0 μ m in wavelength. About 50% of the solar radiation energy is in the visible spectral region (wavelength 0.4~0.76 μ m), and 7% is in the ultraviolet spectral region (wavelength 0.76 μ m), Maximum energy At a wavelength of 0.475 microns. Since the wavelength of solar radiation is higher than that of ground and Atmospheric radiation The wavelength (about 3-120 μ m) is much smaller, so it is also called solar radiation Shortwave radiation , called ground and atmospheric radiation Long wave radiation 。 solar activity The change of the distance from the sun to the earth will cause the change of the solar radiation energy in the upper boundary of the earth's atmosphere. The solar radiation passes through the atmosphere and some reaches the ground, which is called direct solar radiation; The other part is absorption, scattering and reflection of atmospheric molecules, dust and water vapor in the atmosphere. One part of the scattered solar radiation returns to the space, and the other part reaches the ground. The part that reaches the ground is called the scattered solar radiation. The sum of scattered solar radiation and direct solar radiation reaching the ground is called total radiation. When solar radiation passes through the atmosphere, its intensity and spectral energy distribution change. Ratio of solar radiation energy reaching the ground Upper bound of atmosphere Much smaller, in Solar spectrum The upper energy is distributed in the ultraviolet Spectral region Almost extinct, reduced to 40% in the visible spectrum and increased to 60% in the infrared spectrum.

Astronomical radiation The spatiotemporal variation characteristics of are as follows: ① Throughout the year, the equator receives the most radiation, while the polar region receives the least radiation. This heat is not uniform distribution , which will inevitably lead to differences in temperature at different latitudes of the earth's surface, and tropical, temperate and Cold Climate ；② Astronomical radiation is larger in summer and smaller in winter, which leads to higher temperature in summer and lower temperature in winter. Weakening effect of atmosphere on solar radiation It includes the absorption, scattering and reflection of solar radiation by the atmosphere. When solar radiation passes through the whole atmosphere ultraviolet rays Almost all are absorbed in the visible light area Atmospheric absorption very seldom. There are strong Absorption band 。 The substances in the atmosphere that absorb solar radiation mainly include oxygen, ozone, water vapor and Liquid water , followed by carbon dioxide 、 methane 、 Nitrous oxide And dust, etc. Clouds can strongly absorb and scatter solar radiation, and also strongly absorb solar radiation reflected from the ground. Average of cloud reflectivity 0.50-0.55. Reaching the ground after atmospheric weakening Direct solar radiation and Scattered radiation The sum is called Total solar radiation 。 On the global average, the total solar radiation only accounts for 45% of the solar radiation reaching the upper boundary of the atmosphere. total Radiation It decreases with latitude and increases with altitude. The maximum value is around noon and 0 at night in a day; Summer is big and winter is small in a year.

electromagnetic radiation

electromagnetic wave (also known as electromagnetic radiation ）Is created by in-phase Oscillating and mutually perpendicular electric and magnetic fields move in the form of waves in space, and their propagation direction is perpendicular to the plane composed of electric and magnetic fields, effectively transferring energy and momentum. Electromagnetic radiation can be classified according to frequency, from low frequency to high frequency, including radio waves , microwave infrared 、 visible light , UV, (ionizing radiation) X-ray and Gamma ray wait. The electromagnetic radiation that can be received by the human eye, whose wavelength is about 380 to 780 nm, is called visible light 。 As long as the temperature is greater than Absolute zero All objects can emit electromagnetic radiation, and there is no object whose temperature is equal to or lower than absolute zero in the world. Therefore, all objects around people are conducting electromagnetic radiation at all times. However, only in the visible light frequency domain The internal electromagnetic waves can be seen by people. Electromagnetic waves do not need to rely on media to propagate. The speed of various electromagnetic waves is fixed in vacuum, and the speed is the speed of light.^[1]

1. Common Electromagnetic radiation source Generally speaking, radar system, TV, mobile phone and radio transmission system, radio frequency induction and media heating equipment , RF and microwave Medical equipment , various Electromachining Equipment, communication transmitting station, satellite earth Communication station , large power stations, power transmission and transformation equipment, high voltage and EHV transmission Line, subway train, electric train and most household appliances are all electromagnetic radiation sources that can produce various forms, different frequencies and different intensities.

2. Electromagnetic

Division of radiation field area: electromagnetic radiation field area is generally divided into Far-field and Near-field 。

3.1. Near field and characteristics: centered on the field source Wavelength range The inner region is usually called the near-field, or Induction field 。 The near field usually has the following characteristics: within the near field, electric field intensity And magnetic field intensity The size of is not proportional. That is, E ¹ 377H. Generally, for field sources with high voltage and low current (such as Transmitting antenna 、 feeder The electric field is much stronger than the magnetic field. For the field source with low voltage and large current (such as some Induction heating equipment The magnetic field is much larger than the electric field. The electromagnetic field intensity in the near field is much larger than that in the far field. From this point of view, electromagnetic protection should focus on the near field. The electromagnetic field intensity of the near field changes rapidly with distance Uniformity Larger.

3.2 The far-field and its characteristics are that the space range with the field source as the center and the radius outside of a wavelength is called far-field, or far-field radiation field 。 The main characteristics of the far-field are as follows: In the far-field, all electromagnetic energy basically radiates and propagates in the form of electromagnetic waves radiation intensity The attenuation of is much slower than the induction field. In the far field, the relationship between electric field strength and magnetic field strength is as follows: International System of Units In, E=377H, the running directions of electric field and magnetic field are perpendicular to each other, and both are perpendicular to the propagation direction of electromagnetic wave. The far field is Weak field The electromagnetic field strength is small.

3.3 Significance of the division of near field and far field: Generally, for a fixed electromagnetic radiation source that can produce a certain intensity, the electromagnetic field intensity of the near field radiation is large, so we should pay special attention to the protection of the near field of electromagnetic radiation. In addition, should Yes As for the concept of near-field, we are most familiar with the frequency range from 30MHz in short wave band to 3000MHz in micro wave band, and the wavelength range is from 10m to 0.1m.

thermal radiation

thermal radiation , is used for an object electromagnetic radiation A form of heat transfer in which heat is dissipated. It does not depend on any external conditions. It is one of the three main modes of heat conduction.

Any object is emitting radiant energy At the same time, it also continuously absorbs the radiation energy from the surrounding objects. The difference between the energy radiated by an object and the energy absorbed by it is the net energy transmitted by it. The radiant capacity of an object (that is, the energy radiated from a unit surface in a unit time) increases rapidly with the increase of temperature.

The heat effect occurs when the radiant energy is absorbed by the object. The temperature generated by the different radiant energy absorbed by the object is also different. Therefore, radiation is energy conversion An important way for heat. Radiant heat transfer (radial heat transfer) Electromagnetic wave radiation Realize between hot and cold objects Heat transfer It is a non-contact heat transfer process that can also be carried out in vacuum. In theory, the electromagnetic waves emitted by objects are distributed in the whole spectrum range, but in the temperature range encountered in industry, what is of practical significance is the thermal radiation whose wavelength is between 0.38 and 1000 μ m, and most of them are located in infrared (also known as Thermal radiation ）0.76~20 μ m in the section. so-called Infrared heating Is to use the heat radiation in this section. It is very important to study the heat radiation law for the reasonable design of heat transfer in the furnace High temperature furnace jockey Of labor protection It is also of positive significance. When a system needs insulation, even if the temperature of the system is not high, the impact of radiation heat transfer cannot be ignored. as vacuum flask Silver plating on the gallbladder is to reduce the radiation heat transfer Heat loss 。

Generally speaking, when an object is radiated by other objects (energy is Q), the part absorbed into heat energy is QA, the part reflected is QR, and the part through the object is QD. Obviously, there is a relationship between these parts and the total energy as shown in the following formula:

QA+QR+QD=Q If A=QA/Q is called absorptivity , R=QR/Q is called reflectivity, D=QD/Q is called reflectivity Penetration ，

Then: A+R+D=1 If the object's A=1, R=D=0, that is, the energy of the thermal radiation reaching the object's surface is completely absorbed. This object is called Absolute blackbody , referred to as boldface.

If R=1, A=D=0, the energy of thermal radiation reaching the surface of the object is fully reflected;

When the reflection is regular, the object is called a mirror; If it is random reflection, it is called Absolute white body 。

If D=1, A=R=0, that is, the energy of the thermal radiation reaching the surface of the object passes through the object completely. This object is called Diathermy 。

In fact, there is no absolute black body and absolute white body, only some objects are close to absolute black body or absolute white body.

For example: matte Black paint The surface is close to the black body, and its absorption rate is 0.97~0.98; The polished copper surface is close to White body Its reflectivity can reach 0.97.

The absorption and reflection properties of solid surface are mainly affected by the surface condition and color, and the influence of surface condition is often greater than that of color. Solids and liquids are generally impermeable to heat. The energy of thermal radiation passes through the surface of a solid or liquid only after a short distance (generally less than 1mm, and passes through the metal surface only 1 μ m), and is then Complete absorption 。 The gas has almost no ability to reflect the thermal radiation energy. Single atom and symmetric diatomic gas (such as Ar 、 He , H2.N2.O2, etc.), can be regarded as a heat permeable body, Polyatomic gas (e.g. CO2 H2O 、 SO2 、 NH3 , CH4, etc.) Absorptive capacity 。

influence factor

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Weak interaction yes 4 kinds in nature Basic interaction one of. abbreviation Weak action 。 The weak interaction is Elementary particle A special function between it and Strong interaction ， Electromagnetic action and Universal gravitation Function and become four types Basic interaction force 。

The first weak effect phenomenon observed is Nucleus Of Beta decay 。 Later, it was observed that meson 、 baryon and Lepton Through the decay of weak action and neutrino Scattering and other weak interaction processes. Weak acting Range of force It is the shortest of the four functions low-energy The process can be approximately regarded as the action of particles participating in the weak interaction process at the same point.

After analyzing the experiment, we found that, Fermion The weak action at one point (called Fermi action) is two Fermion Weakly active coupling The so-called weak interaction current is equivalent to the current of electromagnetic action. Coupling constant G And Proton mass Quadratic The product of is Dimensionless Specific to electromagnetic action Fine structure constant 1000 times smaller. This ratio reflects the difference in the intensity of the two actions at low energy.

Another feature of weak interaction is Symmetry Low. In weak interaction, spatial reflection Charge conjugation and Time inversion The symmetry of is destroyed; isospin 、 Singular number 、 Charm number 、 base number Wait at Strong action Lower conserved Quantum number all Nonconservation 。 However, the weak effect of failure time inversion is much weaker than that of non failure time inversion.

Weak interaction and Electromagnetic interaction Although very different, there are similarities. The weak interaction current is conserved as the current, and there is a relationship between them based on symmetry.

There are two weak interactions, one is Lepton (Electronic e, neutrino ν， Muon And their Antiparticle ）Participating reactions, such as beta decay, positive beta decay, muon decay and Pion Decay, etc; The other one is "K" meson And Λ Hyperon The decay of. The strength of the two weak interactions is the same, both are 10 ^ 12 times weaker than the strong interaction, and the interaction time is about 10 ^ (- 6)~10 ^ (- 8) s.

Protons and neutrons can interact through the following weak interaction processes: 1. Protons+electrons=(reversible) neutrons+ Electron neutrino 2. Protons+ Antielectron neutrino =Neutron+ positron

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electromagnetic radiation and Electromagnetic radiation pollution difference

Electromagnetic radiation and Electromagnetic radiation pollution Are two concepts, any Charged body There is electromagnetic radiation when Electromagnetic radiation intensity exceed national standard Will produce negative effects and cause different pathological changes and hazards to the human body, which exceed the standard electromagnetic field Intensity radiation is called electromagnetic radiation pollution.

mobile phone Base station radiation Impact on human body

Mobile phone radiation And mobile phones Base station radiation Is different. Generally, the electromagnetic radiation value of a mobile phone is 0.03-0.7, while the radiation value of a mobile phone base station is 10 microwatts. The radiation value generated by a mobile phone base station is much higher than that of a mobile phone. In addition, the closer the distance and the longer the radiation time are, the deeper the damage will be. The distance from the mobile phone base station installed on the roof of ordinary residential buildings to us is safe distance , so the impact is relatively small.

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