Radiation: its types and effects on the body. What is radiation in physics? Definition, features, application of radiation in physics
§ 1. Thermal radiation
In the process of studying the radiation of heated bodies, it was found that any heated body emits electromagnetic waves (light) in a wide frequency range. Hence, thermal radiation is the radiation of electromagnetic waves due to the internal energy of the body.
Thermal radiation occurs at any temperature. However, at low temperatures, practically only long (infrared) electromagnetic waves are emitted.
We carry the following quantities characterizing the radiation and absorption of energy by bodies:
energy luminosityR(T) is the energy W emitted by 1 m 2 of the surface of a luminous body in 1 s.
W / m 2.
body emissivity r(λ,T) ( or spectral density of energy luminosity)- this is the energy in a single wavelength interval emitted by 1 m 2 of the surface of a luminous body in 1 s.
. 
.
Here 
is the radiation energy with wavelengths from λ to 
.
The relationship between the integral energy luminosity and the spectral density of energy luminosity is given by the following relation:
.
.
It was experimentally established that the ratio of the emitting and absorbing abilities does not depend on the nature of the body. This means that it is the same (universal) function of the wavelength (frequency) and temperature for all bodies. This empirical law was discovered by Kirchhoff and bears his name.
Kirchhoff's law: the ratio of emitting and absorbing abilities does not depend on the nature of the body, it is for all bodies the same (universal) function of the wavelength (frequency) and temperature:
.
A body that at any temperature completely absorbs all the radiation incident on it is called an absolutely black body of an A.C.T.
Absorption capacity of a black body a.ch.t. (λ,T) is equal to one. This means that the universal Kirchhoff function 
is identical to the emissivity of a perfect black body 
. Thus, to solve the problem of thermal radiation, it was necessary to establish the form of the Kirchhoff function or the emissivity of an absolutely black body.
Analyzing experimental data and applying the methods of thermodynamics Austrian physicists Joseph Stefan(1835 - 1893) and Ludwig Boltzmann(1844-1906) in 1879 partially solved the problem of A.Ch.T radiation. They received a formula for determining the energy luminosity of an a.ch.t. – R acht (T). According to the Stefan-Boltzmann law
,
.
IN 
In 1896, German physicists led by Wilhelm Wien created a super-modern experimental setup for those times to study the distribution of radiation intensity over wavelengths (frequencies) in the spectrum of thermal radiation of a black body. The experiments performed on this facility: firstly, confirmed the result obtained by the Austrian physicists J. Stefan and L. Boltzmann; secondly, graphs of the distribution of the intensity of thermal radiation over wavelengths were obtained. They were surprisingly similar to the distribution curves of gas molecules in a closed volume, obtained earlier by J. Maxwell, according to the velocities.
The theoretical explanation of the resulting graphs became the central problem of the late 90s of the 19th century.
English classical physics lord Rayleigh(1842-1919) and sir James Jeans(1877-1946) applied to thermal radiation methods of statistical physics(we used the classical law on the equipartition of energy over degrees of freedom). Rayleigh and Jeans applied the method of statistical physics to waves in the same way that Maxwell applied it to an equilibrium ensemble of randomly moving particles in a closed cavity. They assumed that for each electromagnetic oscillation there is an average energy equal to kT ( 
for electricity and 
to magnetic energy). Based on these considerations, they obtained the following formula for the emissivity of an A.Ch.T.:
.
E 
This formula described well the course of the experimental dependence at long wavelengths (at low frequencies). But for short wavelengths (high frequencies or in the ultraviolet region of the spectrum), the classical theory of Rayleigh and Jeans predicted an infinite increase in radiation intensity. This effect is called the ultraviolet catastrophe.
Assuming that the same energy corresponds to a standing electromagnetic wave of any frequency, Rayleigh and Jeans neglected the fact that higher and higher frequencies contribute to the radiation as the temperature rises. Naturally, the model adopted by them should have led to an infinite increase in the radiation energy at high frequencies. The ultraviolet catastrophe has become a serious paradox of classical physics.
WITH 
The next attempt to obtain a formula for the dependence of the emissivity of an A.Ch.T. from wavelengths undertook Vin. With methods classical thermodynamics and electrodynamics
Blame succeeded in deriving a relation whose graphical representation satisfactorily coincided with the short-wave (high-frequency) part of the data obtained in the experiment, but absolutely diverged from the results of experiments for long wavelengths (low frequencies).
.
From this formula, a relation was obtained relating that wavelength 
, which corresponds to the maximum radiation intensity, and the absolute temperature of the body T (Wien's displacement law):
,
.
This was consistent with the experimental results obtained by Wien, from which it followed that with increasing temperature, the maximum of the radiation intensity shifted towards shorter wavelengths.
But there was no formula describing the entire curve.
Then Max Planck (1858-1947), who at that time worked in the department of physics at the Berlin Kaiser Wilhelm Institute, took up the solution to the problem. Planck was a very conservative member of the Prussian Academy, completely absorbed in the methods of classical physics. He was passionate about thermodynamics. Practically, from the moment of defending his dissertation in 1879, and almost until the end of the century, for twenty years in a row, Planck was engaged in the study of problems related to the laws of thermodynamics. Planck understood that classical electrodynamics cannot answer the question of how the energy of equilibrium radiation is distributed over wavelengths (frequencies). The problem that arose was related to the field of thermodynamics. Planck investigated the irreversible process of establishing an equilibrium between matter and radiation (light). In order to bring theory into agreement with experience, Planck deviated from classical theory in only one point: he accepted the hypothesis that light emission occurs in portions (quanta). The hypothesis accepted by Planck made it possible to obtain such an energy distribution over the spectrum for thermal radiation, which corresponded to the experiment.
.
On December 14, 1900, Planck presented his results to the Berlin Physical Society. Thus, quantum physics was born.
The radiation energy quantum introduced by Planck into physics turned out to be proportional to the radiation frequency 
(and inversely proportional to the wavelength):
.
is the universal constant, now called Planck's constant. It is equal to: 
.
Light is a complex material object that has both wave and particle properties.
Wave parameters– wavelength 
, light frequency 
and wave number 
.
Corpuscular characteristics– energy 
and momentum 
.
The wave parameters of light are related to its corpuscular characteristics using Planck's constant:
.
Here 
And 
is the wave number.
Planck's constant plays a fundamental role in physics. This dimensional constant makes it possible to quantify how important quantum effects are in the description of each specific physical system.
When, according to the conditions of the physical problem, Planck's constant can be considered a negligible quantity, a classical (non-quantum) description is sufficient.
For those who are not familiar with physics or are just starting to study it, the question of what radiation is is a difficult one. But with this physical phenomenon, we meet almost every day. To put it simply, radiation is the process of the propagation of energy in the form of electromagnetic waves and particles, or, in other words, these are energy waves propagating around.
Radiation source and its types
The source of electromagnetic waves can be both artificial and natural. For example, X-rays are referred to as artificial radiation.
You can feel the radiation without even leaving your home: you just have to hold your hand over a burning candle, and immediately you will feel the radiation of heat. It can be called thermal, but besides it, there are several other types of radiation in physics. Here are some of them:
- Ultraviolet - this radiation a person can feel on himself while sunbathing in the sun.
- X-rays have the shortest wavelengths, they are called x-rays.
- Even a person can see infrared rays, an example of this is an ordinary children's laser. This type of radiation is produced by the coincidence of microwave radio emissions and visible light. Often infrared radiation is used in physiotherapy.
- Radioactive radiation is formed during the decay of chemical radioactive elements. You can learn more about radiation from the article.
- Optical radiation is nothing but light radiation, light in the broadest sense of the word.
- Gamma radiation is a type of electromagnetic radiation with a short wavelength. It is used, for example, in radiation therapy.
Scientists have long known that some radiation adversely affects the human body. How strong this effect will be depends on the duration and power of the radiation. If you expose yourself to radiation for a long time, this can lead to changes at the cellular level. All electronic equipment that surrounds us, be it a mobile phone, a computer or a microwave oven - all this has an impact on health. Therefore, care must be taken not to expose yourself to excess radiation.
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Every person is exposed to different types of radiation every day. For those who are not familiar with physical phenomena, they have a poor idea of what this process means and where it comes from.
Radiation in physics- this is the formation of a new electromagnetic field, which is formed during the reaction of particles charged with an electric current, in other words, this is a certain stream of electromagnetic waves that propagate around.
Properties of the radiation process
This theory was laid down by Faraday M. in the 19th century, and continued and developed by Maxwell D. It was he who was able to give all studies a strict mathematical formula.
Maxwell was able to deduce and structure Faraday's laws, from which he determined that all electromagnetic waves travel at the same speed of light. Thanks to his work, some phenomena and actions in nature became explainable. As a result of his findings, the emergence of electrical and radio technology became possible.
Charged particles determine the characteristic features of radiation. Also, the process is strongly influenced by the interaction of charged particles with the magnetic fields to which it tends.
For example, when it interacts with atomic substances, the speed of the particle changes, it first slows down, and then stops moving further, in science this phenomenon is called bremsstrahlung.
You can meet different types of this phenomenon, some created by nature itself, while others with the help of human intervention.
However, the very law of changing the type of cure is the same for all. The electromagnetic field is separated from the charged element, but it moves at the same speed.
The characteristic of the field directly depends on the speed with which the movement itself occurs, as well as the size of the charged particle. If it does not collide with anything while moving, then its speed does not change and, therefore, it does not create radiation.
But if during the movement it collides with different particles, then the speed changes, part of its own field is disconnected, and turns into a free one. It turns out that the formation of magnetic waves occurs only when the speed of the particle changes.
Various factors can affect the speed, hence different types of radiation are formed, for example, it can be brake radiation. There are also dipole, multipole radiation, they are formed when a particle inside itself changes the existing structure.
It is important that the field always has momentum, energy.
Since during the interaction of a positron and an electron, the formation of free fields is possible, while charged particles retain momentum, energy, which is transferred to the electromagnetic field.
Sources and types of radiation
Electromagnetic waves originally existed in nature, in the process of development and creation of new laws of physics, new sources of radiation appeared, which are called artificial, created by man. One of these types is X-rays.
In order to feel this process for yourself, you do not need to leave the apartment. Electromagnetic waves surround a person everywhere, just turn on the light or light a candle. Raising your hand to a light source, you can feel the heat that objects radiate. Such a phenomenon is called.
However, there are other types of it, for example, in the summer months, going to the beach, a person receives ultraviolet radiation, which comes from the sun's rays.
Every year, at the medical examination, they undergo such a procedure as fluorography, in order to perform a medical examination, special X-ray equipment is used, which also gives radiation.
It is also used in medicine, most often used in physiotherapy of patients. This type is also used in children's lasers. Radiation therapy is also used in the treatment of certain diseases. This type is called a gamma because the wavelengths are very short.
This phenomenon is possible due to the complete coincidence of charged particles that interact with the light source.
Many have heard about radiation, it is also one of the types of radiation.
It is formed during the decay of chemical elements that are radioactive, that is, the process occurs due to the fact that the nuclei of particles are split into atoms, and they emit radioactive waves. Radio, television for their broadcasting use radio waves, the waves they emit have a long wavelength.
The emergence of radiation
The electric dipole is the simplest element producing the phenomenon. However, the process creates a certain system, which consists of two particles, oscillating in different ways.
If the particles are in a straight line, when moving towards each other, then a part of the electromagnetic field is disconnected, and charged waves are formed.
In physics, such a phenomenon is called non-isotopic, since the resulting energy does not have the same strength. In this case, the speed and location of the elements are not important, since real emitters must have a large number of elements that have a charge.
The initial state can be changed if the charged particles of the same name begin to pull together to the nucleus, where the distribution of charges occurs. Such a connection can be regarded as an electric dipole, since the resulting system will be of a completely electrically neutral type.
If there is no dipole, then it is possible to create a process using a quadrupole. Also in physics, a more complex system is distinguished for receiving radiation - this is a multipole.
For the formation of such particles, it is necessary to use a circuit with a current; then, when moving, the occurrence of quadrupole radiation is possible. It is important to consider that the intensity of the magnetic type is much less than that of the electric type.
Radiation reaction
In the process of interaction, the particle loses part of its own energy, since a certain force affects it when moving. It, in turn, affects the speed of the flow of waves, with its action, the acting force of movement slows down. This process is called radiation friction.
With this reaction, the force of the process will be very small, but the speed will be very high and close to the speed of light. This phenomenon can be considered on the example of our planet.
The magnetic field contains quite a lot of energy, so the electrons that are emitted from space cannot reach the surface of the planet. However, there are particles of cosmic waves that can reach the earth. Such elements should have a high loss of their own energy.
The dimensions of the region of space are also highlighted, this value is important for radiation. This factor affects the formation of the electromagnetic radiation field.
In this state of motion, the particles are not large, but the speed of detaching the field from the element is equal to light, and it turns out that the creation process will be very active. And as a result, short electromagnetic waves are obtained.
In the case when the speed of the particle is high, and is approximately equal to light, then the time for detaching the field increases, this process lasts quite a long time and, therefore, electromagnetic waves have a long length. Since their path took longer than usual, and the formation of the field took quite a long time.
In quantum physics, radiation is also used, but when considering completely different elements, these can be molecules, atoms. In this case, the phenomenon of radiation is considered and obeys the laws of quantum mechanics.
Thanks to the development of science, it became possible to make corrections and change the characteristics of radiation.
Many studies have shown that radiation can adversely affect the human body. It all depends on what kind of radiation, and how long the person was exposed to it.
It's no secret that during a chemical reaction and the decay of nuclear molecules, radiation can occur, which is dangerous for living organisms.
When they decay, instantaneous and rather strong irradiation can occur. Surrounding objects can also emit radiation, such as cell phones, microwave ovens, laptops.
These objects send, as a rule, short electromagnetic waves. However, accumulation can occur in the body, which affects health.
A person is constantly under the influence of various external factors. Some of them are visible, such as weather conditions, and the degree of their impact can be controlled. Others are not visible to the human eye and are called radiations. Everyone should know the types of radiation, their role and applications.
Some types of radiation can be found everywhere. Radio waves are a prime example. They are vibrations of an electromagnetic nature that can be distributed in space at the speed of light. Such waves carry energy from generators.
Radio wave sources can be divided into two groups.
- Natural, these include lightning and astronomical units.
- Artificial, that is, man-made. They include emitters with alternating current. These can be radio communication devices, broadcasting, computers and navigation systems.
Human skin is capable of depositing this type of waves on its surface, so there are a number of negative consequences of their impact on a person. Radio wave radiation can slow down the activity of brain structures, as well as cause mutations at the gene level.
For people who have a pacemaker installed, such exposure is deadly. These devices have a clear maximum allowable level of radiation, the rise above it introduces an imbalance in the operation of the stimulator system and leads to its breakdown.
All the effects of radio waves on the body have been studied only on animals, there is no direct evidence of their negative effects on humans, but scientists are still looking for ways to protect themselves. As such, there are no effective methods yet. The only thing that can be advised is to stay away from dangerous devices. Since household appliances connected to the network also create a radio wave field around themselves, it is simply necessary to turn off the power of devices that a person is not using at the moment.
Infrared radiation
All types of radiation are interconnected in one way or another. Some of them are visible to the human eye. Infrared radiation is adjacent to that part of the spectrum that the human eye can catch. It not only illuminates the surface, but is also able to heat it.
The main natural source of IR rays is the sun. Man has created artificial emitters, through which the necessary thermal effect is achieved.
Now we need to figure out how useful or harmful this type of radiation is for humans. Almost all long-wavelength infrared radiation is absorbed by the upper layers of the skin, therefore, it is not only safe, but also able to increase immunity and enhance regenerative processes in tissues.
As for short waves, they can go deep into tissues and cause overheating of organs. The so-called thermal shock is a consequence of exposure to short infrared waves. The symptoms of this pathology are known to almost everyone:
- the appearance of spinning in the head;
- feeling of nausea;
- increase in heart rate;
- visual disturbances characterized by darkening of the eyes.
How to protect yourself from dangerous influence? It is necessary to observe safety precautions, using heat-protective clothing and screens. The use of short-wave heaters must be clearly dosed, the heating element must be covered with a heat-insulating material, with the help of which radiation of soft long waves is achieved.
If you think about it, all types of radiation can penetrate tissue. But it was X-ray radiation that made it possible to use this property in practice in medicine.
If we compare X-rays with rays of light, then the former have a very long length, which allows them to penetrate even through opaque materials. Such rays are not able to be reflected and refracted. This type of spectrum has a soft and hard component. Soft consists of long waves that can be completely absorbed by human tissues. Thus, constant exposure to long waves leads to cell damage and DNA mutation.
Currently, devices have been created that allow not only to take a fixed picture, for example, of a limb, but also to observe the changes taking place with it “online”. These devices help the doctor to perform surgical intervention on the bones under the control of vision, without making wide traumatic incisions. With the help of such devices, it is possible to study the biomechanics of the joints.
As for the negative effects of X-rays, prolonged contact with them can lead to the development of radiation sickness, which manifests itself in a number of ways:
- neurological disorders;
- dermatitis;
- decreased immunity;
- inhibition of normal hematopoiesis;
- development of oncological pathology;
- infertility.
To protect yourself from terrible consequences, when in contact with this type of radiation, you need to use shielding shields and linings made of materials that do not transmit rays.
People used to call this type of rays simply - light. This type of radiation is able to be absorbed by the object of influence, partially passing through it and partially reflected. Such properties are widely used in science and technology, especially in the manufacture of optical instruments.
All sources of optical radiation are divided into several groups.
- Thermal, having a continuous spectrum. The heat in them is released due to the current or the combustion process. These can be electric and halogen incandescent lamps, as well as pyrotechnic products and electric lighting devices.
- Luminescent, containing gases excited by photon fluxes. Such sources are energy-saving devices and cathodoluminescent devices. As for radio- and chemiluminescent sources, the fluxes in them are excited due to the products of radioactive decay and chemical reactions, respectively.
- Plasma, whose characteristics depend on the temperature and pressure of the plasma formed in them. These can be gas discharge, mercury tubular and xenon lamps. Spectral sources, as well as devices of a pulsed nature, are no exception.
Optical radiation on the human body acts in combination with ultraviolet radiation, which provokes the production of melanin in the skin. Thus, the positive effect lasts until the exposure threshold is reached, beyond which there is a risk of burns and skin oncopathology.
The most famous and widely used radiation, the effects of which can be found everywhere, is ultraviolet radiation. This radiation has two spectra, one of which reaches the earth and participates in all processes on earth. The second is delayed by the ozone layer and does not pass through it. The ozone layer neutralizes this spectrum, thereby performing a protective role. The destruction of the ozone layer is dangerous by the penetration of harmful rays to the surface of the earth.
The natural source of this type of radiation is the Sun. A huge number of artificial sources have been invented:
- Erythema lamps that activate the production of vitamin D in the layers of the skin and help treat rickets.
- Solariums, not only allowing you to sunbathe, but also having a therapeutic effect for people with pathologies caused by a lack of sunlight.
- Laser emitters used in biotechnology, medicine and electronics.
As for the impact on the human body, it is twofold. On the one hand, the lack of ultraviolet radiation can cause various diseases. A dosed load with such radiation helps the immune system, the functioning of muscles and lungs, and also prevents hypoxia.
All types of influences are divided into four groups:
- the ability to kill bacteria;
- removal of inflammation;
- restoration of damaged tissues;
- pain reduction.
The negative effects of ultraviolet radiation include the ability to provoke skin cancer with prolonged exposure. Skin melanoma is an extremely malignant type of tumor. Such a diagnosis almost 100 percent means impending death.
With regard to the organ of vision, excessive exposure to ultraviolet rays damages the retina, cornea and membranes of the eye. Thus, it is necessary to use this type of radiation in moderation. If, under certain circumstances, it is necessary to contact the source of ultraviolet rays for a long time, then it is necessary to protect the eyes with glasses, and the skin with special creams or clothing.
These are the so-called cosmic rays, which carry the nuclei of atoms of radioactive substances and elements. The flow of gamma radiation has a very high energy and is able to quickly penetrate into the cells of the body, ionizing their contents. Destroyed cellular elements act like poisons, decomposing and poisoning the entire body. The nucleus of cells is necessarily involved in the process, which leads to mutations in the genome. Healthy cells are destroyed, and mutant cells are formed in their place, unable to fully provide the body with everything necessary.
This radiation is dangerous because a person does not feel it in any way. The effects of exposure do not appear immediately, but have a long-term effect. First of all, the cells of the hematopoietic system, hair, genitals and lymphoid system suffer.
Radiation is very dangerous for the development of radiation sickness, but even this spectrum has found useful applications:
- with its help, products, equipment and instruments for medical purposes are sterilized;
- measuring the depth of underground wells;
- measurement of the path length of spacecraft;
- impact on plants in order to identify productive varieties;
- in medicine, such radiation is used for radiation therapy in the treatment of oncology.
In conclusion, it must be said that all types of rays are successfully used by man and are necessary. Thanks to them, plants, animals and people exist. Protection from overexposure should be a top priority when working.