Hazards from infrared radiation. Introduction. Infrared radiation, infrared rays, properties of infrared rays, radiation spectrum of infrared heaters

William Herschel first noticed that behind the red edge of the prism-derived spectrum of the Sun there was invisible radiation that caused the thermometer to heat up. This radiation was later called thermal or infrared.

Near-infrared radiation is very similar to visible light and is detected by the same instruments. Mid- and far-IR uses bolometers to detect changes.

The entire planet Earth and all objects on it, even ice, shine in the mid-IR range. Due to this, the Earth is not overheated by solar heat. But not all infrared radiation passes through the atmosphere. There are only a few windows of transparency; the rest of the radiation is absorbed by carbon dioxide, water vapor, methane, ozone and other greenhouse gases that prevent the Earth from rapidly cooling.

Due to atmospheric absorption and thermal radiation from objects, mid- and far-IR telescopes are taken into space and cooled to the temperature of liquid nitrogen or even helium.

The infrared range is one of the most interesting for astronomers. It contains cosmic dust, important for the formation of stars and the evolution of galaxies. IR radiation passes through clouds of cosmic dust better than visible radiation and allows one to see objects that are inaccessible to observation in other parts of the spectrum.

Sources

A fragment of one of the so-called Hubble Deep Fields. In 1995, a space telescope collected light coming from one part of the sky for 10 days. This made it possible to see extremely faint galaxies up to 13 billion light years away (less than one billion years from the Big Bang). Visible light from such distant objects undergoes a significant red shift and becomes infrared.

The observations were carried out in a region far from the galactic plane, where relatively few stars are visible. Therefore, most of the registered objects are galaxies at different stages of evolution.

The giant spiral galaxy, also designated M104, is located in a cluster of galaxies in the constellation Virgo and is visible to us almost edge-on. It has a huge central bulge (a spherical thickening in the center of the galaxy) and contains about 800 billion stars - 2-3 times more than the Milky Way.

At the center of the galaxy is a supermassive black hole with a mass of about a billion solar masses. This is determined by the speed of movement of stars near the center of the galaxy. In the infrared, a ring of gas and dust is clearly visible in the galaxy, in which stars are actively being born.

Receivers

Main mirror diameter 85 cm made of beryllium and cooled to a temperature of 5.5 TO to reduce the mirror's own infrared radiation.

The telescope was launched in August 2003 under the program NASA's four great observatories, including:

Compton Gamma-ray Observatory (1991–2000, 20 keV-30 GeV), see Sky at 100 MeV gamma rays,
Chandra X-ray Observatory (1999, 100 eV-10 keV),
Hubble Space Telescope (1990, 100–2100 nm),
Spitzer infrared telescope (2003, 3–180 µm).

The Spitzer telescope is expected to have a lifespan of about 5 years. The telescope received its name in honor of astrophysicist Lyman Spitzer (1914–97), who in 1946, long before the launch of the first satellite, published the article “Advantages for Astronomy of an Extraterrestrial Observatory,” and 30 years later convinced NASA and the American Congress to begin developing a space telescope. Hubble."

Sky Reviews

Near-infrared sky 1–4 µm and in the mid-infrared range 25 µm(COBE/DIRBE)

In the near-infrared range, the Galaxy is visible even more clearly than in the visible.

But in the mid-IR range the Galaxy is barely visible. Observations are greatly hampered by dust in the solar system. It is located along the ecliptic plane, which is inclined to the galactic plane at an angle of about 50 degrees.

Both surveys were obtained by the DIRBE (Diffuse Infrared Background Experiment) instrument on board the COBE (Cosmic Background Explorer) satellite. This experiment, begun in 1989, produced complete maps of infrared sky brightness ranging from 1.25 to 240 µm.

Terrestrial Application

The device is based on an electron-optical converter (EOC), which allows one to significantly (from 100 to 50 thousand times) amplify weak visible or infrared light.

The lens creates an image on the photocathode, from which, as in the case of a PMT, electrons are knocked out. Then they are accelerated by high voltage (10–20 kV), are focused by electron optics (an electromagnetic field of a specially selected configuration) and fall onto a fluorescent screen similar to a television. On it, the image is viewed through eyepieces.

Acceleration of photoelectrons makes it possible in low light conditions to use literally every quantum of light to obtain an image, but in complete darkness a backlight is required. In order not to reveal the presence of an observer, they use a near-infrared illuminator (760–3000 nm).

There are also devices that detect objects’ own thermal radiation in the mid-IR range (8–14 µm). Such devices are called thermal imagers; they allow you to notice a person, animal or heated engine due to their thermal contrast with the surrounding background.

All the energy consumed by an electric heater ultimately turns into heat. A significant part of the heat is carried away by air, which comes into contact with the hot surface, expands and rises, so that mainly the ceiling is heated.

To avoid this, heaters are equipped with fans that direct warm air, for example, to a person’s feet and help mix the air in the room. But there is another way to transfer heat to surrounding objects: infrared radiation from a heater. The hotter the surface and the larger its area, the stronger it is.

To increase the area, radiators are made flat. However, the surface temperature cannot be high. Other heater models use a spiral heated to several hundred degrees (red heat) and a concave metal reflector that creates a directed stream of infrared radiation.

Brake Equilibrium Monochromatic Cherenkovskoe Transitional Radio emissions Microwave Terahertz Infrared Visible Ultraviolet X-ray Gamma radiation Ionizing Relict Magnetic drift Two-photon Forced

Infrared radiation- electromagnetic radiation, occupying the spectral region between the red end of visible light (with wavelength λ = 0.74 μm) and microwave radiation (λ ~ 1-2 mm).

Infrared radiation was discovered in 1800 by the English scientist W. Herschel.

Now the entire range of infrared radiation is divided into three components:

short-wave region: λ=0.74 - 2.5 µm;
mid-wave region: λ=2.5 - 50 µm;
long-wave region: λ=50 - 2000 µm;

Recently, the long-wave edge of this range has been separated into a separate, independent range of electromagnetic waves - terahertz radiation(submillimeter radiation).

Infrared radiation is also called “thermal” radiation, since all bodies, solid and liquid, heated to a certain temperature, emit energy in the infrared spectrum. In this case, the wavelengths emitted by the body depend on the heating temperature: the higher the temperature, the shorter the wavelength and the higher the radiation intensity. The radiation spectrum of an absolutely black body at relatively low (up to several thousand Kelvin) temperatures lies mainly in this range.

Usage

IR (infrared) diodes and photodiodes are widely used in remote controls, automation systems, security systems, etc. They do not distract human attention due to their invisibility. Infrared emitters are used in industry for drying paint surfaces. The infrared drying method has significant advantages over the traditional convection method. First of all, this is, of course, an economic effect. The speed and energy consumed during infrared drying is less than the same indicators with traditional methods. A positive side effect is also the sterilization of food products, increasing the corrosion resistance of painted surfaces. The disadvantage is the significantly greater unevenness of heating, which is completely unacceptable in a number of technological processes. A special feature of the use of IR radiation in the food industry is the possibility of penetration of an electromagnetic wave into capillary-porous products such as grain, cereals, flour, etc. to a depth of up to 7 mm. This value depends on the nature of the surface, structure, material properties and frequency characteristics of the radiation. An electromagnetic wave of a certain frequency range has not only a thermal, but also a biological effect on the product, helping to accelerate biochemical transformations in biological polymers (

From the history of the study of infrared radiation

Infrared radiation or thermal radiation is not a discovery of the 20th or 21st century. Infrared radiation was discovered in 1800 by an English astronomer W. Herschel. He discovered that the "maximum heat" lies beyond the red color of visible radiation. This study marked the beginning of the study of infrared radiation. Many famous scientists have put their heads into the study of this area. These are names such as: German physicist Wilhelm Wien(Wien's law), German physicist Max Planck(Planck's formula and constant), Scottish scientist John Leslie(thermal radiation measuring device - Leslie cube), German physicist Gustav Kirchhoff(Kirchhoff's radiation law), Austrian physicist and mathematician Josef Stefan and Austrian physicist Stefan Ludwig Boltzmann(Stefan-Boltzmann law).

The use and application of knowledge of thermal radiation in modern heating devices only came to the fore in the 1950s. In the USSR, the theory of radiant heating was developed in the works of G. L. Polyak, S. N. Shorin, M. I. Kissin, A. A. Sander. Since 1956, many technical books on this topic have been written or translated into Russian in the USSR. Due to changes in the cost of energy resources and in the struggle for energy efficiency and energy conservation, modern infrared heaters are widely used in heating domestic and industrial buildings.

Solar radiation - natural infrared radiation

The most famous and significant natural infrared heater is the Sun. Essentially, it is nature's most advanced heating method known to mankind. Within the Solar System, the Sun is the most powerful source of thermal radiation that determines life on Earth. At a solar surface temperature of about 6000K the maximum radiation occurs at 0.47 µm(corresponds to yellowish-white). The sun is located at a distance of many millions of kilometers from us, however, this does not prevent it from transmitting energy through this entire vast space, practically without consuming it (energy), without heating it (space). The reason is that solar infrared rays travel a long way in space and have virtually no energy loss. When any surface is encountered on the path of the rays, their energy, being absorbed, turns into heat. The Earth, which is hit by the sun's rays, and other objects that are also hit by the sun's rays are heated directly. And the earth and other objects heated by the Sun, in turn, give off heat to the air around us, thereby heating it.

Both the power of solar radiation at the earth's surface and its spectral composition most significantly depend on the height of the Sun above the horizon. Different components of the solar spectrum pass through the earth's atmosphere differently.
At the Earth's surface, the spectrum of solar radiation has a more complex shape, which is associated with absorption in the atmosphere. In particular, it does not contain the high-frequency part of ultraviolet radiation, which is harmful to living organisms. At the outer boundary of the earth's atmosphere, the flux of radiant energy from the Sun is 1370 W/m²; (solar constant), and the maximum radiation occurs at λ=470 nm(Blue colour). The flux reaching the earth's surface is significantly less due to absorption in the atmosphere. Under the most favorable conditions (the sun at its zenith) it does not exceed 1120 W/m²; (in Moscow, at the moment of the summer solstice - 930 W/m²), and the maximum radiation occurs at λ=555 nm(green-yellow), which corresponds to the best sensitivity of the eyes and only a quarter of this radiation occurs in the long-wave radiation region, including secondary radiation.

However, the nature of solar radiant energy is quite different from the radiant energy given off by infrared heaters used for space heating. The energy of solar radiation consists of electromagnetic waves, the physical and biological properties of which differ significantly from the properties of electromagnetic waves emanating from conventional infrared heaters, in particular, the bactericidal and healing (heliotherapy) properties of solar radiation are completely absent from radiation sources with low temperatures. And yet infrared heaters provide the same thermal effect, as the Sun, being the most comfortable and economical of all possible heat sources.

The nature of infrared rays

Outstanding German physicist Max Planck, while studying thermal radiation (infrared radiation), discovered its atomic nature. Thermal radiation- this is electromagnetic radiation emitted by bodies or substances and arising due to its internal energy, due to the fact that the atoms of a body or substance move faster under the influence of heat, and in the case of a solid material, they oscillate faster compared to the equilibrium state. During this movement, atoms collide, and when they collide, they are excited by shock, followed by the emission of electromagnetic waves.
All objects continuously emit and absorb electromagnetic energy. This radiation is a consequence of the continuous movement of elementary charged particles inside matter. One of the basic laws of classical electromagnetic theory states that a charged particle moving with acceleration emits energy. Electromagnetic radiation (electromagnetic waves) is a disturbance of the electromagnetic field propagating in space, that is, a time-varying periodic electromagnetic signal in space consisting of electric and magnetic fields. This is thermal radiation. Thermal radiation contains electromagnetic fields of various wavelengths. Since atoms move at any temperature, all bodies are at any temperature greater than the temperature of absolute zero (-273°С), emit heat. The energy of electromagnetic waves of thermal radiation, that is, the strength of the radiation, depends on the temperature of the body, its atomic and molecular structure, as well as on the state of the surface of the body. Thermal radiation occurs at all wavelengths - from the shortest to the extremely long, but only that thermal radiation of practical importance that occurs in the wavelength range is taken into account: λ = 0.38 – 1000 µm(in the visible and infrared parts of the electromagnetic spectrum). However, not all light has the characteristics of thermal radiation (for example, luminescence), therefore, only the infrared spectrum can be taken as the main range of thermal radiation (λ = 0.78 – 1000 µm). You can also make an addition: a section with a wavelength λ = 100 – 1000 µm, from a heating point of view - not interesting.

Thus, thermal radiation is one of the forms of electromagnetic radiation that arises due to the internal energy of the body and has a continuous spectrum, that is, it is part of electromagnetic radiation, the energy of which, when absorbed, causes a thermal effect. Thermal radiation is inherent in all bodies.

All bodies that have a temperature greater than absolute zero (-273°C), even if they do not glow with visible light, are a source of infrared rays and emit a continuous infrared spectrum. This means that the radiation contains waves with all frequencies without exception, and it is completely pointless to talk about radiation at any particular wave.

The main conventional areas of infrared radiation

Today there is no unified classification for dividing infrared radiation into its component areas (areas). In the target technical literature there are more than a dozen schemes for dividing the infrared radiation region into component areas, and they all differ from each other. Since all types of thermal electromagnetic radiation are of the same nature, the classification of radiation by wavelength depending on the effect they produce is only conditional and is determined mainly by differences in detection technology (type of radiation source, type of meter, its sensitivity, etc. .) and in the technique of measuring radiation. Mathematically, using formulas (Planck, Wien, Lambert, etc.), it is also impossible to determine the exact boundaries of the regions.
To determine the wavelength (maximum radiation), there are two different formulas (temperature and frequency) that give different results, with a difference of approximately 1,8 times (this is the so-called Wien's displacement law) and plus, all calculations are made for an ABSOLUTELY BLACK BODY (idealized object), which does not exist in reality. Real bodies found in nature do not obey these laws and, to one degree or another, deviate from them. The radiation of real bodies depends on a number of specific characteristics of the body (surface condition, microstructure, layer thickness, etc.). This is also the reason why different sources indicate completely different values for the boundaries of the radiation regions. All this suggests that temperature must be used to describe electromagnetic radiation with great care and with an order of magnitude accuracy. I emphasize once again that the division is very arbitrary!!!

Let us give examples of conditional division of the infrared region (λ = 0.78 – 1000 µm) to individual areas (information taken only from the technical literature of Russian and foreign scientists). The above figure shows how diverse this division is, so you should not get attached to any of them. You just need to know that the spectrum of infrared radiation can be divided into several sections, from 2 to 5. The region that is closer to the visible spectrum is usually called: near, near, short-wave, etc. The region that is closer to microwave radiation is far, far, long-wave, etc. According to Wikipedia, the usual division scheme looks like this: Near area(Near-infrared, NIR), Shortwave region(Short-wavelength infrared, SWIR), Medium wave region(Mid-wavelength infrared, MWIR), Long wavelength region(Long-wavelength infrared, LWIR), Far area(Far-infrared, FIR).

Properties of infrared rays

Infrared rays- This is electromagnetic radiation, which has the same nature as visible light, therefore it is also subject to the laws of optics. Therefore, in order to better imagine the process of thermal radiation, we should draw an analogy with light radiation, which we all know and can observe. However, we must not forget that the optical properties of substances (absorption, reflection, transparency, refraction, etc.) in the infrared region of the spectrum differ significantly from the optical properties in the visible part of the spectrum. A characteristic feature of infrared radiation is that, unlike other main types of heat transfer, there is no need for a transmitting intermediate substance. Air, and especially vacuum, is considered transparent to infrared radiation, although this is not entirely true with air. When infrared radiation passes through the atmosphere (air), a slight weakening of thermal radiation is observed. This is due to the fact that dry and clean air is almost transparent to heat rays, but if it contains moisture in the form of steam, water molecules (H 2 O), carbon dioxide (CO 2), ozone (O 3) and other solid or liquid suspended particles that reflect and absorb infrared rays, it becomes a not entirely transparent medium and, as a result, the flow of infrared radiation is scattered in different directions and weakens. Typically, scattering in the infrared region of the spectrum is less than in the visible. However, when the losses caused by scattering in the visible region of the spectrum are large, they are also significant in the infrared region. The intensity of the scattered radiation varies in inverse proportion to the fourth power of the wavelength. It is significant only in the short-wave infrared region and decreases rapidly in the longer wavelength part of the spectrum.

Nitrogen and oxygen molecules in the air do not absorb infrared radiation, but attenuate it only as a result of scattering. Suspended dust particles also lead to scattering of infrared radiation, and the amount of scattering depends on the ratio of particle sizes and wavelength of infrared radiation; the larger the particles, the greater the scattering.

Water vapor, carbon dioxide, ozone and other impurities present in the atmosphere selectively absorb infrared radiation. For example, water vapor very strongly absorbs infrared radiation throughout the entire infrared region of the spectrum, and carbon dioxide absorbs infrared radiation in the mid-infrared region.

As for liquids, they can be either transparent or opaque to infrared radiation. For example, a layer of water several centimeters thick is transparent to visible radiation and opaque to infrared radiation with a wavelength of more than 1 micron.

Solids(bodies), in turn, in most cases not transparent to thermal radiation, but there are exceptions. For example, silicon wafers, opaque in the visible region, are transparent in the infrared region, and quartz, on the contrary, is transparent to light radiation, but opaque to thermal rays with a wavelength of more than 4 microns. It is for this reason that quartz glass is not used in infrared heaters. Ordinary glass, unlike quartz glass, is partially transparent to infrared rays; it can also absorb a significant part of infrared radiation in certain spectral ranges, but does not transmit ultraviolet radiation. Rock salt is also transparent to thermal radiation. Metals, for the most part, have a reflectivity for infrared radiation that is much greater than for visible light, which increases with increasing wavelength of infrared radiation. For example, the reflectance of aluminum, gold, silver and copper at a wavelength of about 10 µm reaches 98% , which is significantly higher than for the visible spectrum, this property is widely used in the design of infrared heaters.

It is enough to give here as an example the glazed frames of greenhouses: glass practically transmits most of the solar radiation, and on the other hand, the heated earth emits waves of long length (about 10 µm), in relation to which glass behaves like an opaque body. Thanks to this, the temperature inside the greenhouses is maintained for a long time, much higher than the temperature of the outside air, even after solar radiation stops.

Radiant heat transfer plays an important role in human life. A person transfers to the environment the heat generated during the physiological process, mainly through radiant heat exchange and convection. With radiant (infrared) heating, the radiant component of heat transfer from the human body is reduced due to the higher temperature that occurs both on the surface of the heating device and on the surface of some internal enclosing structures, therefore, while providing the same warm sensation, convective heat loss may be greater, those. The room temperature may be lower. Thus, radiant heat exchange plays a decisive role in the formation of a person’s feeling of thermal comfort.

When a person is in the range of an infrared heater, IR rays penetrate the human body through the skin, and different layers of the skin reflect and absorb these rays in different ways.

With infrared long wave radiation the penetration of rays is significantly less compared to shortwave radiation. The absorption capacity of moisture contained in skin tissue is very high, and the skin absorbs more than 90% of the radiation reaching the surface of the body. The nerve receptors that sense heat are located in the outermost layer of the skin. The absorbed infrared rays excite these receptors, which causes a feeling of warmth in a person.

Infrared rays have both local and general effects. Shortwave infrared radiation, unlike long-wave infrared radiation, can cause redness of the skin at the site of irradiation, which reflexively spreads 2-3 cm around the irradiated area. The reason for this is that the capillary vessels dilate and blood circulation increases. A blister may soon appear at the site of radiation, which later turns into a scab. Also when hit shortwave infrared rays to the organs of vision, cataracts may occur.

The possible consequences of exposure listed above shortwave IR heater, should not be confused with impact long-wave IR heater. As already mentioned, long-wave infrared rays are absorbed at the very top of the skin layer and cause only a simple thermal effect.

The use of radiant heating should not endanger a person or create an uncomfortable microclimate in the room.

Radiant heating can provide comfortable conditions at lower temperatures. When using radiant heating, the indoor air is cleaner because the air flow speed is lower, which reduces dust pollution. Also, with this heating, dust decomposition does not occur, since the temperature of the radiating plate of a long-wave heater never reaches the temperature necessary for dust decomposition.

The colder the heat emitter, the more harmless it is for the human body, the longer a person can stay in the heater’s area of effect.

Prolonged stay of a person near a HIGH TEMPERATURE heat source (more than 300°C) is harmful to human health.

Impact of infrared radiation on human health.

How the human body emits infrared rays, and absorbs them. IR rays penetrate the human body through the skin, and different layers of the skin reflect and absorb these rays differently. Long-wave radiation penetrates the human body significantly less compared to shortwave radiation. Moisture in the skin tissue absorbs more than 90% of the radiation reaching the surface of the body. The nerve receptors that sense heat are located in the outermost layer of the skin. The absorbed infrared rays excite these receptors, which causes a feeling of warmth in a person. Short-wave infrared radiation penetrates the body most deeply, causing its maximum heating. As a result of this effect, the potential energy of the body's cells increases, and unbound water will leave them, the activity of specific cellular structures increases, the level of immunoglobulins increases, the activity of enzymes and estrogens increases, and other biochemical reactions occur. This applies to all types of body cells and blood. However Long-term exposure to short-wave infrared radiation on the human body is undesirable. It is on this property that it is based heat treatment effect, widely used in physiotherapy rooms in our and foreign clinics, and note that the duration of procedures is limited. However, the data restrictions do not apply to long-wave infrared heaters. Important characteristic infrared radiation– wavelength (frequency) of radiation. Modern research in the field of biotechnology has shown that it is long-wave infrared radiation is of exceptional importance in the development of all forms of life on Earth. For this reason it is also called biogenetic rays or life rays. Our body radiates itself long infrared waves, but it itself also needs constant feeding long wave heat. If this radiation begins to decrease or there is no constant replenishment of the human body with it, then the body is attacked by various diseases, the person quickly ages against the background of a general deterioration in well-being. Further infrared radiation normalizes the metabolic process and eliminates the cause of the disease, and not just its symptoms.

With such heating, you will not have a headache from the stuffiness caused by overheated air under the ceiling, as when working convective heating, - when you constantly want to open the window and let fresh air in (while letting out heated air).

When exposed to infrared radiation with an intensity of 70-100 W/m2, the activity of biochemical processes in the body increases, which leads to an improvement in the general condition of a person. However, there are standards and they should be followed. There are standards for safe heating of domestic and industrial premises, for the duration of medical and cosmetic procedures, for working in HOT workshops, etc. Don't forget about this. When infrared heaters are used correctly, there is COMPLETELY NO negative impact on the body.

Infrared radiation, infrared rays, properties of infrared rays, radiation spectrum of infrared heaters

INFRARED RADIATION, INFRARED RAYS, PROPERTIES OF INFRARED RAYS, RADIATION SPECTRUM OF INFRARED HEATERS Kaliningrad

HEATERS PROPERTIES RADIATION SPECTRUM OF HEATERS WAVELENGTH LONG WAVE MEDIUM WAVE SHORT WAVE LIGHT DARK GRAY HARM HEALTH IMPACT ON HUMAN Kaliningrad

> Infrared waves

What's happened infrared waves: Infrared wavelength, infrared wave range and frequency. Study infrared spectrum patterns and sources.

Infrared light(IR) - electromagnetic rays, which in terms of wavelengths exceed the visible (0.74-1 mm).

Learning Objective

Understand the three ranges of the IR spectrum and describe the processes of absorption and emission by molecules.

Basic moments

IR light accommodates most of the thermal radiation produced by bodies at approximately room temperature. Emitted and absorbed when changes occur in the rotation and vibration of molecules.
The IR part of the spectrum can be divided into three regions according to wavelength: far infrared (300-30 THz), mid-infrared (30-120 THz) and near-infrared (120-400 THz).
IR is also called thermal radiation.
It is important to understand the concept of emissivity to understand IR.
IR rays can be used to remotely determine the temperature of objects (thermography).

Terms

Thermography is the remote calculation of changes in body temperature.
Thermal radiation is electromagnetic radiation generated by a body due to temperature.
Emissivity is the ability of a surface to emit radiation.

Infrared waves

Infrared (IR) light is electromagnetic rays whose wavelengths exceed visible light (0.74-1 mm). The infrared wavelength range converges with the 300-400 THz frequency range and accommodates enormous amounts of thermal radiation. IR light is absorbed and emitted by molecules as they change in rotation and vibration.

Here are the main categories of electromagnetic waves. Dividing lines differ in some places, and other categories may overlap. Microwaves occupy the high-frequency portion of the radio section of the electromagnetic spectrum

Subcategories of IR waves

The IR portion of the electromagnetic spectrum occupies the range from 300 GHz (1 mm) to 400 THz (750 nm). There are three types of infrared waves:

Far IR: 300 GHz (1 mm) to 30 THz (10 µm). The lower part can be called microwaves. These rays are absorbed due to rotation in gas-phase molecules, molecular motions in liquids and photons in solids. Water in the earth's atmosphere is absorbed so strongly that it becomes opaque. But there are certain wavelengths (windows) used for transmission.
Mid-IR range: 30 to 120 THz (10 to 2.5 µm). The sources are hot objects. Absorbed by molecular vibrations (various atoms vibrate in equilibrium positions). This range is sometimes called a fingerprint because it is a specific phenomenon.
Nearest IR range: 120 to 400 THz (2500-750 nm). These physical processes resemble those that occur in visible light. The highest frequencies can be found with a certain type of photographic film and sensors for infrared, photography and video.

Heat and thermal radiation

Infrared radiation is also called thermal radiation. IR light from the Sun captures just 49% of the Earth's heating, with the rest being visible light (absorbed and re-reflected at longer wavelengths).

Heat is energy in a transitional form that flows due to differences in temperature. If heat is transferred by conduction or convection, then radiation can propagate in a vacuum.

To understand IR rays, we need to take a close look at the concept of emissivity.

IR Wave Sources

Humans and most of the planetary environment produce heat rays at 10 microns. This is the boundary separating the mid- and far-IR regions. Many astronomical bodies emit detectable amounts of IR rays at non-thermal wavelengths.

IR rays can be used to calculate the temperature of objects at a distance. This process is called thermography and is most actively used in military and industrial applications.

Thermographic image of a dog and cat

IR waves are also used in heating, communications, meteorology, spectroscopy, astronomy, biology and medicine, and art analysis.

Infrared radiation is invisible to the human eye, however, it is emitted by all liquid and solid substances. It ensures the occurrence of many processes on Earth. It is used in various areas of our activities.

All properties of infrared radiation on the body have been studied by phototherapists. The effect depends on the wavelength and duration of exposure. They are indispensable for a normal life.

The IR range ranges from the red end of the visible spectrum to the violet (ultraviolet) spectrum. This interval is divided into areas: long, medium and short. In low beam the beams are more dangerous. But long-wavelengths have a beneficial effect on the body.

Benefits of infrared radiation:

use in medicine to treat various diseases;
scientific research - assistance in discoveries;
has a beneficial effect on plant growth;
application in the food industry to accelerate biochemical transformations;
food sterilization;
ensures the operation of equipment - radios, telephones, and others;
production of various devices and devices based on infrared;
use for military purposes for the safety of the population.

The negative aspects of shortwave IR are due to the heating temperature. The higher it is, the stronger the radiation intensity.

Harmful properties of short IR:

when exposed to the eyes - cataracts;
in case of contact with skin - burns, blisters;
if it affects the brain – nausea, dizziness, increased heart rate;
When using heaters with IR, you should not be in close proximity.

Sun– the main natural generator of IR. Approximately 50% of its radiation is in the infrared spectrum. Thanks to them, life began. Solar energy is directed to objects with a lower temperature and heats them.

The earth absorbs it and returns most of it to the atmosphere. All objects have different radiating properties, which may have a dependence on several bodies.

Artificial derivatives include many items equipped with LEDs. These are incandescent lamps, tungsten filaments, heaters, and some lasers. Almost everything that surrounds us is both a source and an absorber of IR. Any heated body emits invisible light.

Application

Infrared rays are used in medicine, everyday life, industry, and astronomy. They cover many areas in human life. Wherever he goes, wherever he is, he experiences infrared influence.

Use in medicine

Since ancient times, people have noticed the healing power of heat to treat diseases. Many disorders are caused by unfavorable environmental conditions. Throughout life, the body accumulates harmful substances.

Infrared radiation has long been used in medicine. Long-wave IR has the most useful properties. Research has proven that such therapy stimulates the body to eliminate toxins, alcohol, nicotine, lead, and mercury.

It normalizes the metabolic process, strengthens the immune system, many infections disappear, and not only the symptoms disappear, but also the disease itself. Health clearly becomes stronger: blood pressure decreases, good sleep appears, muscles relax, blood vessels dilate, blood flow accelerates, mood improves, mental stress goes away.

Treatment methods can focus directly on the diseased area or affect the entire body.

A feature of local physiotherapy is the targeted effect of IR on diseased parts of the body. General procedures are designed for the entire body. Improvement occurs after just a few sessions.

An example of the main diseases for which IR therapy is indicated:

musculoskeletal system – fractures, arthritis, joint inflammation;
respiratory system – asthma, bronchitis, pneumonia;
nervous system – neuralgia, restless sleep, depression;
urinary apparatus – renal failure, cystitis, prostatitis;
skin – burns, ulcers, scars, inflammatory processes, psoriasis;
cosmetology – anti-cellulite effect;
dentistry – removal of nerves, installation of fillings;
diabetes;
elimination of radioactive exposure.

This list does not reflect all aspects in medicine where infrared rays are used.

Physiotherapy has contraindications: pregnancy, blood diseases, individual intolerance, pathologies during exacerbation, tuberculosis, neoplasms, purulent processes, tendency to bleeding.

Infrared heater

IR heaters are becoming more and more popular. This is explained by significant advantages from an economic and social approach.

It has long been established in industry and agriculture that electromagnetic devices do not dissipate heat, but heat the desired object by focusing infrared radiation in the form of a wave directly onto the object. So, in a large workshop, the workplace is heated, but in a warehouse, the person’s route is heated, and not the entire room.

Central heating is provided using hot water in radiators. The temperature distribution is uneven, heated air rises to the ceiling, and in the parquet area it is clearly colder. In the case of an infrared heater, the problem of wasted heat can be avoided.

Installations in combination with natural ventilation reduce air humidity to normal; for example, on pig farms and barns, sensors record 70-75% or less. When using such an emitter, the number of animals increases.

Infrared spectroscopy

The branch of physics responsible for the influence of infrared on bodies is called infrared spectroscopy. With its help, problems of quantitative and qualitative analysis of mixtures of substances, the study of intermolecular interactions, and the study of the kinetics and characteristics of chemical reaction intermediates are solved.

This method measures the vibrations of molecules using a spectrometer. It has a large tabular database that allows you to identify thousands of substances based on their atomic fingerprint.

Remote control

Used to control devices from a distance. Infrared diodes are used mainly in home appliances. For example, a TV remote control, some smartphones have an IR port.

These rays do not interfere, because invisible to human eyes.

Thermography

Thermal imaging in infrared rays is used for diagnostic purposes, also in printing, veterinary medicine and other fields.

With various diseases, body temperature changes. The circulatory system increases intensity in the area of disturbances, which is reflected on the instrument monitor.

Cool shades are dark blue, the increase in warmth is noticeable by the color changing first to green, then yellow, red and white.

Properties of IR rays

IR rays have the same nature as visible light, but are in a different range. In this regard, they obey the laws of optics and are endowed with emissivity, reflection, and transmission coefficients.

Distinctive characteristics:

a specific feature is the absence of the need for an intermediate link during heat transfer;
the ability to pass through some opaque bodies;
heats the substance by being absorbed by it;
invisible;
has a chemical effect on photographic plates;
causes an internal photoelectric effect in germanium;
capable of wave optics (interference and diffraction);
recorded using photographic methods.

Infrared radiation in life

A person emits and absorbs infrared rays. They have local and general effects. And what the consequences will be - benefit or harm, depends on their frequency.

Long infrared waves are emitted from people, and it is desirable to receive them back. Physiotherapeutic treatment is based on them. After all, they trigger the mechanism of regeneration and healing of organs.

Short waves have a different operating principle. They can cause internal organs to heat up.

Also, prolonged exposure to ultraviolet rays leads to consequences such as burns or even oncology. Medical experts do not recommend spending time in the sun during the day, especially if you have a child with you.