Every day a person is under the influence of infrared radiation and its natural source is the sun. Incandescent elements and various electric heaters are classified as unnatural derivatives.. This radiation is used in heating systems, infrared lamps, heating devices, TV remote controls, and medical equipment. Therefore, it is always necessary to know what are the benefits and harms of infrared radiation for humans.

Infrared radiation: what is it

In 1800, an English physicist discovered infrared heat by decomposing sunlight into a spectrum using a prism.. William Herschel applied a thermometer to each color until he noticed an increase in temperature from purple to red. Thus, the area of ​​sensation of heat was opened, but it is not visible to the human eye. Radiation is distinguished by two main parameters: frequency (intensity) and beam length. At the same time, the wavelength is divided into three types: near (from 0.75 to 1.5 microns), medium (from 1.5 to 5.6 microns), far (from 5.6 to 100 microns).

It is long-wave energy that has positive properties, corresponding to the natural radiation of the human body with the largest wavelength of 9.6 microns. Therefore, every external influence the body perceives as "native". The best example of infrared radiation is the heat of the Sun. Such a beam has the difference that it heats the object, not the space around it. Infrared radiation is a heat dissipation option.

The benefits of infrared radiation

Devices that use long-wave thermal radiation affect the human body in two different ways. The first method has a strengthening property, increasing protective functions and preventing early aging. This type allows you to cope with various diseases, increasing the body's natural defense against ailments. It is a form of health care treatment that is suitable for use at home and in health care settings.

The second type of influence of infrared rays is the direct treatment of diseases and general ailments. On a daily basis, a person is faced with health-related disorders. Therefore, long emitters have a therapeutic property. In many medical institutions in America, Canada, Japan, the CIS countries and Europe, such radiation is used. Waves are able to penetrate deeply into the body, warming up the internal organs and the skeletal system. These effects help to improve blood circulation and accelerate the flow of fluids in the body.

Increased blood circulation has a beneficial effect on human metabolism, tissues are saturated with oxygen, and the muscular system receives nutrition. Many diseases can be eliminated by regular exposure to radiation that penetrates deep into the human body. This wavelength will relieve such ailments as:

• high or low blood pressure;
• pain in the back;
• overweight, obesity;
• diseases of the cardiovascular system;
• depression, stress;
• disorders of the digestive tract;
• arthritis, rheumatism, neuralgia;
• arthrosis, inflammation of the joints, cramps;
• malaise, weakness, exhaustion;
• bronchitis, asthma, pneumonia;
• sleep disorder, insomnia;
• muscle and lumbar pain;
• problems with blood supply, blood circulation;
• otorhinolaryngological diseases without purulent deposits;
• skin ailments, burns, cellulite;
• kidney failure;
• colds and viral illnesses;
• decrease in the protective function of the body;
• intoxication;
• cystitis and prostatitis of an aggravated form;
• cholecystitis without stone formation, gastroduodenitis.

The positive effect of radiation is based on the fact that when the wave hits the skin, it acts on the endings of the nerves and there is a feeling of warmth. Over 90% of the radiation is destroyed by the moisture in the top layer of the skin, it causes nothing more than an increase in body temperature. The spectrum of action, the length of which is 9.6 microns, is absolutely safe for humans.

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Radiation stimulates blood circulation, normalizing blood pressure and metabolic processes. When the brain tissues are supplied with oxygen, the risk of dizziness is reduced and memory is improved. The infrared beam is able to remove salts of heavy metals, cholesterol and toxins. During therapy, the patient's immunity increases, the hormonal background normalizes and the water-salt balance is restored. Waves reduce the effect of various toxic chemicals, have anti-inflammatory properties, and inhibit the formation of fungi, including molds.

Application of infrared radiation

Infrared energy is used in different areas, positively affecting a person:

1. Thermography. With the help of infrared radiation, the temperature of objects located at a distance is determined. Thermal waves are mainly used in the military and industrial sectors. Heated objects with such a device can be seen without lighting.
2. Heating. Infrared rays contribute to an increase in temperature, having a beneficial effect on human health. In addition to useful infrared saunas, they are used for welding, annealing plastic objects, curing surfaces in the industrial and medical fields.
3. Tracking. This way of using thermal energy is passive guidance of missiles. These flying elements have a mechanism called a "thermal seeker" inside. Cars, planes and other vehicles, as well as people, radiate heat to help rockets find the right direction to fly.
4. Meteorology. Radiation helps satellites determine the distance at which clouds are located, determines their temperature and type. Warm clouds are shown in gray and cold clouds in white. The data is studied without interference both day and night. The terrestrial hot plane will be indicated in gray or black.
5. Astronomy. Astronomers are equipped with unique devices - infrared telescopes, which allow them to observe various objects in the sky. Thanks to them, scientists are able to find protostars before they begin to emit light visible to the human eye. Such a telescope will easily detect cold objects, but planets cannot be seen in the viewed infrared spectrum due to the drowning light from the stars. The device is also used to observe the nuclei of galaxies, which are covered by gas and dust.
6. Art. Reflectograms, which work on the basis of infrared radiation, help specialists in this field to examine in more detail the lower layers of an object or an artist's sketches. This method allows you to compare the drawings of the drawing and its visible part to determine the authenticity of the painting, and whether it was under restoration. Previously, the device was adapted for studying old documents in writing and making ink.

These are only the main methods of using thermal energy in science, but new equipment based on it appears every year.

Harm of infrared radiation

Infrared light brings not only a positive effect on the human body, it is worth remembering the harm that it can cause if used incorrectly and be dangerous to others. It is the IR ranges with a short wavelength that negatively affect. The bad effect of infrared radiation on the human body manifests itself in the form of inflammation of the lower layers of the skin, dilated capillaries and blistering.

The use of infrared rays must be immediately abandoned in case of such diseases and symptoms:

• diseases of the circulatory system, bleeding;
• chronic or acute form of purulent processes;
• pregnancy and lactation;
• malignant tumors;
• pulmonary and heart failure;
• acute inflammation;
• epilepsy;
• with prolonged exposure to infrared radiation, the risk of developing photophobia, cataracts and other eye diseases increases.

Strong exposure to infrared radiation leads to reddening of the skin and burns. Workers in the metallurgy industry sometimes develop heat stroke and dermatitis. The shorter the user's distance to the heating element, the less time he should spend near the device. Overheating of the brain tissue by one degree and heat stroke is accompanied by symptoms such as nausea, dizziness, tachycardia, darkening in the eyes. With an increase in temperature of two or more degrees, there is a risk of developing meningitis.

If heatstroke occurs under the influence of infrared radiation, immediately place the victim in a cool room and remove all clothing that constricts or restricts movement. Bandages soaked in cold water or ice packs are applied to the chest, neck, groin, forehead, spine, and armpits.

In the absence of an ice bag, any fabric or piece of clothing can be used for this purpose. Compresses are made only with very cold water, periodically wetting the dressings in it.

If possible, a person completely wraps himself in a cold sheet. Additionally, you can blow the patient with a stream of cold air using a fan. Drinking plenty of cold water will help alleviate the condition of the victim. In severe cases of exposure, you need to call an ambulance and give artificial respiration.

How to avoid the harmful effects of IR waves

To protect yourself from the negative effects of heat waves, you must adhere to some rules:

1. If the work is directly related to high-temperature heaters, then use of protective clothing to protect the body and eyes is required.
2. Household heaters with exposed heating elements are used with extreme caution. You can not be close to them and it is better to reduce the time of their influence to a minimum.
3. The room should be equipped with devices that have the least impact on a person and his health.
4. Don't stay in the sun for a long time. If this cannot be changed, then you need to constantly wear a hat and clothes that cover open areas of the body. This is especially true for children, who can not always determine the increase in body temperature.

Subject to these rules, a person will be able to protect himself from the unpleasant consequences of excessive thermal influence. Infrared rays can bring both harm and benefit in certain applications.

Treatment Methods

Infrared color therapy is divided into two types: local and general. In the first type, there is a local effect on a particular area, and with general treatment, the waves treat the entire human body. The procedure is carried out twice a day for 15-30 minutes. The course of treatment is from 5 to 20 sessions. Be sure to wear protective equipment when exposed to radiation. For the eyes, cardboard linings or special glasses are used. After the procedure, redness with blurred borders appears on the skin, which disappears after an hour after exposure to the rays. Infrared radiation is highly valued in medicine.

High intensity radiation can be harmful to health, so you need to follow all contraindications.

Thermal energy daily accompanies a person in everyday life. Infrared radiation brings not only benefits, but also harm. Therefore, it is required to treat infrared light with care. Devices that emit these waves must be used in accordance with safety regulations. Many do not know whether thermal exposure is harmful, but with the correct use of devices, one can improve a person’s health and get rid of certain diseases.

Light is the key to the existence of living organisms on Earth. There are a huge number of processes that can occur due to the influence of infrared radiation. In addition, it is used for medicinal purposes. Since the 20th century, light therapy has become a significant component of traditional medicine.

Features of radiation

Phototherapy is a special section in physiotherapy that studies the effects of a light wave on the human body. It was noted that the waves have a different range, so they affect the human body in different ways. It is important to note that radiation has the largest penetration depth. As for the surface effect, ultraviolet has it.

The infrared spectrum (radiation spectrum) has a corresponding wavelength, namely 780 nm. up to 10000 nm. As for physiotherapy, a wavelength is used to treat a person, which ranges in the spectrum from 780 nm. up to 1400 nm. This range of infrared radiation is considered the norm for therapy. In simple terms, the appropriate wavelength is applied, namely a shorter one, capable of penetrating three centimeters into the skin. In addition, the special energy of the quantum, the frequency of radiation, is taken into account.

According to many studies, it has been found that light, radio waves, infrared rays, are of the same nature, since these are varieties of electromagnetic waves that surround people everywhere. These waves power televisions, mobile phones and radios. In simple words, waves allow a person to see the world around them.

The infrared spectrum has a corresponding frequency, the wavelength of which is 7-14 microns, which has a unique effect on the human body. This part of the spectrum corresponds to the radiation of the human body.

As for the objects of the quantum, the molecules do not have the ability to oscillate arbitrarily. Each quantum molecule has a certain set of energy, radiation frequencies, which are stored at the moment of oscillation. However, it is worth considering that air molecules are equipped with a wide range of such frequencies, so the atmosphere is able to absorb radiation in a variety of spectra.

Radiation sources

The sun is the main source of IR.

Thanks to him, objects can be heated to a specific temperature. As a result, thermal energy is emitted in the spectrum of these waves. Then the energy reaches the objects. The process of transferring thermal energy is carried out from objects with a high temperature to a lower one. In this situation, the objects have different radiating properties that depend on several bodies.

Sources of infrared radiation are everywhere, equipped with elements such as LEDs. All modern televisions are equipped with remote controls, as it operates in the appropriate frequency of the infrared spectrum. They include LEDs. Various sources of infrared radiation can be seen in industrial production, for example: in the drying of paint surfaces.

The most prominent representative of an artificial source in Russia was Russian stoves. Almost all people have experienced the influence of such a stove, and also appreciated its benefits. That is why such radiation can be felt from a heated stove or a heating radiator. At present, infrared heaters are very popular. They have a list of advantages compared to the convection option, as they are more economical.

Coefficient value

In the infrared spectrum, there are several varieties of the coefficient, namely:

• radiation;
• reflection coefficient;
• throughput ratio.

So, the emissivity is the ability of objects to radiate the frequency of radiation, as well as the energy of the quantum. May vary according to the material and its properties, as well as temperature. The coefficient has such a maximum cure = 1, but in a real situation it is always less. As for the low ability of radiation, then it is endowed with elements that have a shiny surface, as well as metals. The coefficient depends on temperature indicators.

The reflectance factor gives an indication of the ability of the materials to reflect the frequency of examinations. Depends on the type of materials, properties and temperature indicators. Basically, reflection is present on polished and smooth surfaces.

Transmittance measures the ability of objects to conduct infrared radiation through itself. Such a coefficient directly depends on the thickness and type of material. It is important to note that most of the materials do not have such a factor.

Use in medicine

Light treatment with infrared radiation has become quite popular in the modern world. The use of infrared radiation in medicine is due to the fact that the technique has medicinal properties. Due to this, there is a beneficial effect on the human body. Thermal influence forms a body in tissues, regenerates tissues and stimulates reparation, accelerates physicochemical reactions.

In addition, the body experiences significant improvements, as the following processes occur:

• acceleration of blood flow;
• vasodilation;
• production of biologically active substances;
• muscle relaxation;
• great mood;
• comfortable state;
• good dream;
• pressure reduction;
• removal of physical, psycho-emotional overstrain and so on.

The visible effect of the treatment occurs within a few procedures. In addition to the noted functions, the infrared spectrum has an anti-inflammatory effect on the human body, helps fight infection, stimulates and strengthens the immune system.

Such therapy in medicine has the following properties:

• biostimulating;
• anti-inflammatory;
• detoxification;
• improved blood flow;
• awakening of the secondary functions of the body.

Infrared light radiation, or rather its treatment, has a visible benefit for the human body.

Therapeutic techniques

Therapy is of two types, namely - general, local. With regard to local exposure, the treatment is carried out on a specific part of the patient's body. During general therapy, the use of light therapy is designed for the entire body.

The procedure is carried out twice a day, the duration of the session varies between 15-30 minutes. The general treatment course contains at least five to twenty procedures. Make sure you have infrared protection for the face area ready. Special glasses, cotton wool or cardboard pads are intended for the eyes. After the session, the skin is covered with erythema, namely, redness with blurred boundaries. The erythema disappears an hour after the procedure.

Indications and contraindications for treatment

IC has the main indications for use in medicine:

• diseases of ENT organs;
• neuralgia and neuritis;
• diseases affecting the musculoskeletal system;
• pathology of the eyes and joints;
• inflammatory processes;
• wounds;
• burns, ulcers, dermatoses and scars;
• bronchial asthma;
• cystitis;
• urolithiasis;
• osteochondrosis;
• cholecystitis without stones;
• arthritis;
• gastroduodenitis in a chronic form;
• pneumonia.

Light treatment has positive results. In addition to the therapeutic effect, IR can be dangerous for the human body. This is due to the fact that there are certain contraindications, not observing which can be harmful to health.

If there are the following ailments, then such treatment will be harmful:

• period of pregnancy;
• blood diseases;
• individual intolerance;
• chronic diseases in the acute stage;
• purulent processes;
• active tuberculosis;
• predisposition to bleeding;
• neoplasms.

These contraindications should be taken into account so as not to harm your own health. Too much radiation intensity can cause great harm.

As for the harm of IR in medicine and at work, a burn and severe reddening of the skin can occur. In some cases, people have developed tumors on the face, as they have been in contact with this radiation for a long time. Significant damage from infrared radiation can result in dermatitis, and there is also heat stroke.

Infrared rays are quite dangerous for the eyes, especially in the range up to 1.5 microns. Prolonged exposure has significant harm, as photophobia, cataracts, vision problems appear. Long-term influence of IR is very dangerous not only for people, but for plants. Using optical devices, you can try to correct the problem with vision.

Impact on plants

Everyone knows that IR have a beneficial effect on the growth and development of plants. For example, if you equip a greenhouse with an infrared heater, you can see a stunning result. Heating is carried out in the infrared spectrum, where a certain frequency is observed, and the wave is equal to 50,000 nm. up to 2,000,000 nm.

There are quite interesting facts according to which you can find out that all plants, living organisms, are influenced by sunlight. The radiation of the sun has a specific range, consisting of 290 nm. – 3000 nm. In simple words, radiant energy plays an important role in the life of every plant.

Given interesting and informative facts, it can be determined that plants need light and solar energy, since they are responsible for the formation of chlorophyll and chloroplasts. The speed of light affects stretching, the origin of cells and growth processes, the timing of fruiting and flowering.

The specifics of the microwave oven

Household microwave ovens are equipped with microwaves that are slightly lower than gamma and x-rays. Such furnaces are capable of provoking an ionizing effect that poses a danger to human health. Microwaves are located in the gap between infrared and radio waves, so such furnaces cannot ionize molecules, atoms. Functional microwave ovens do not affect people, as they are absorbed into food, generating heat.

Microwave ovens cannot emit radioactive particles, therefore they do not have a radioactive effect on food and living organisms. That is why you should not worry that microwave ovens can harm your health!

Discovery of infrared radiation
Types of heat transfer
Physical properties
The range of IR waves favorable for humans

The English researcher Herschel W. in 1800, in the process of studying sunlight, found that in the Sun's rays, when they are decomposed into separate spectra using a prism outside the red visible spectrum, the thermometer readings increase. The thermometer placed in this area showed a higher temperature than the calibration thermometer. Later it was found that the properties of these rays are subject to the laws of optics, it turns out that they are of the same nature, with light radiation. Thus, infrared radiation was discovered.

Let's clarify how hot objects give off heat to the objects around them:
heat transfer(heat exchange between bodies in contact or through a separator),
convection(heat transfer by a coolant, liquid or gas from a heat source to colder objects)
thermal radiation(flux of electromagnetic radiation in a specific wavelength range, emitted by a substance based on its internal excess energy).

All objects of the material world around us are sources and at the same time absorbers of thermal radiation.
Thermal radiation, which is based on infrared rays, is a stream of electromagnetic rays that satisfy the laws of optics and are of the same nature as light radiation. The IR beam is located between the red light perceived by a person (0.7 microns) and short-wave radio emission (1 - 2 mm). In addition, the IR region of the spectrum is divided into short-wave (0.7 - 2 microns), medium-wave (from 2 to 5.1 microns), longwave(5.1 - 200 µm). Infrared rays emit all substances liquid and solid, while the wavelength of the emitted wave depends on the temperature of the substance. At higher temperatures, the wavelength emitted by the substance is shorter, but the intensity of the radiation is greater.

In the range of long-wave radiation (from 9 to 11 microns) is the most favorable thermal radiation for humans. Long-wave emitters have a lower radiation surface temperature, they are characterized by dark ones - at a low surface temperature they do not glow (up to 300 ° C). Medium-wave emitters with a higher surface temperature are characterized as gray, with a maximum body temperature they emit short waves, they are called white or light.

Confirmation by Soviet scientists

Physical properties of infrared radiation

For infrared rays, there are a number of differences from the optical properties of visible light. (transparency, reflectance, refractive index) For example, infrared radiation having a wavelength of more than 1 micron, absorbed by water in a layer of 1-2 cm, therefore water in some cases is used as a heat-shielding barrier. The silicon sheet is opaque in the visible region, but transparent in the infrared. A number of metals have reflex qualities which are higher for infrared radiation than for light perceived by a person, in addition, their properties are significantly improved with an increase in the radiation wavelength index. Namely, the reflection index of Al, Au, Ag at a wavelength of about 10 μm approaches 98%. Given these properties of materials, they are used in the manufacture of infrared equipment. Materials that are transparent to infrared rays - as emitters of infrared radiation (quartz, ceramics), materials with a high ability to reflect rays - as reflectors that allow focusing infrared radiation in the right direction (mainly aluminum).

It is also important to know about the absorption and scattering properties of infrared radiation. Infrared rays travel through the air almost unhindered. Namely, the molecules of nitrogen and oxygen by themselves do not absorb infrared rays, but only slightly scatter, reducing the intensity. Water vapor, ozone, carbon dioxide, and other impurities in the air absorb infrared radiation: water vapor - in almost the entire infrared region of the spectrum, carbon dioxide - in the middle part of the infrared region. The presence in the air of small particles - dust, smoke, small drops of liquids leads to a weakening of the strength of infrared radiation as a result of its scattering on these particles.

William Herschel first noticed that beyond the red edge of the Sun's spectrum obtained with a prism, there is invisible radiation that causes 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. In the middle and far IR, bolometers are used to indicate changes.

In the mid-IR range, the entire planet Earth and all objects on it, even ice, shine. 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 cooling rapidly.

Due to absorption in the atmosphere and thermal radiation of objects, mid- and far-infrared telescopes are taken out 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 shines with cosmic dust, which is 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 you 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 accumulated light coming from one part of the sky for 10 days. This made it possible to see extremely faint galaxies, the distance to which is up to 13 billion light years (less than one billion years from the Big Bang). Visible light from such distant objects experiences a significant redshift and becomes infrared.

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

The giant spiral galaxy, also referred to as M104, is located in the 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 from the velocities of the 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 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 four great NASA observatories including:

• Compton Gamma Observatory (1991–2000, 20 keV-30 GeV), see 100 MeV gamma-ray sky,
• X-ray observatory "Chandra" (1999, 100 eV-10 keV),
• Hubble Space Telescope (1990, 100–2100 nm),
• Spitzer Infrared Telescope (2003, 3–180 micron).

It is expected that the lifetime of the Spitzer telescope will be about 5 years. The telescope got its name in honor of the 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 US Congress to start developing a space telescope " Hubble.

sky surveys

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

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

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

Both surveys were obtained by the DIRBE (Diffuse Infrared Background Experiment) instrument aboard the COBE (Cosmic Background Explorer) satellite. This experiment, which began in 1989, produced complete infrared sky brightness maps ranging from 1.25 to 240 micron.

Earth application

The device is based on an electron-optical converter (IOC), which makes it possible 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 PMT, electrons are knocked out. Then they are accelerated by high voltage (10–20 kV), are focused by electronic optics (electromagnetic field of a specially selected configuration) and fall on a fluorescent screen similar to television. On it, the image is viewed through the eyepieces.

The acceleration of photoelectrons makes it possible in low light conditions to use literally every quantum of light to obtain an image, however, in complete darkness, illumination is required. In order not to give out the presence of an observer, a near-IR searchlight (760–3000 nm).

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

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

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

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

Infrared radiation- electromagnetic radiation occupying the spectral region between the red end of visible light (with a wavelength λ = 0.74 microns and a frequency of 430 THz) and microwave radio radiation (λ ~ 1-2 mm, frequency 300 GHz).

The entire range of infrared radiation is conditionally divided into three areas:

The long-wave edge of this range is sometimes distinguished into a separate range of electromagnetic waves - terahertz radiation (submillimeter radiation).

Infrared radiation is also called "thermal radiation", since infrared radiation from heated objects is perceived by the human skin as a sensation of warmth. 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 emission spectrum of an absolutely black body at relatively low (up to several thousand Kelvin) temperatures lies mainly in this range. Infrared radiation is emitted by excited atoms or ions.

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Subtitles

History of discovery and general characteristics

Infrared radiation was discovered in 1800 by the English astronomer W. Herschel. Being engaged in the study of the Sun, Herschel was looking for a way to reduce the heating of the instrument with which observations were made. Using thermometers to determine the effects of different parts of the visible spectrum, Herschel found that the "maximum heat" lies behind the saturated red color and, perhaps, "behind the visible refraction." This study marked the beginning of the study of infrared radiation.

Previously, laboratory sources of infrared radiation were exclusively incandescent bodies or electrical discharges in gases. Now, on the basis of solid-state and molecular gas lasers, modern sources of infrared radiation with adjustable or fixed frequency have been created. To register radiation in the near infrared region (up to ~1.3 μm), special photographic plates are used. A wider sensitivity range (up to about 25 microns) is possessed by photoelectric detectors and photoresistors. Radiation in the far infrared region is recorded by bolometers - detectors sensitive to heating by infrared radiation.

IR equipment is widely used both in military technology (for example, for missile guidance) and in civilian technology (for example, in fiber-optic communication systems). Optical elements in IR spectrometers are either lenses and prisms, or diffraction gratings and mirrors. To avoid absorption of radiation in air, far-IR spectrometers are manufactured in a vacuum version.

Since infrared spectra are associated with rotational and vibrational motions in a molecule, as well as with electronic transitions in atoms and molecules, IR spectroscopy provides important information about the structure of atoms and molecules, as well as the band structure of crystals.

Infrared bands

Objects typically emit infrared radiation across the entire wavelength spectrum, but sometimes only a limited region of the spectrum is of interest because sensors typically only collect radiation within a certain bandwidth. Thus, the infrared range is often subdivided into smaller ranges.

The usual division scheme

The most common division into smaller ranges is as follows:

Abbreviation	Wavelength	Photon energy	Characteristic
Near-infrared, NIR	0.75-1.4 µm	0.9-1.7 eV	Near IR, limited on one side by visible light, on the other - by water transparency, which deteriorates significantly at 1.45 µm. Widespread infrared LEDs and lasers for fiber and airborne optical communication systems operate in this range. Video cameras and night vision devices based on image intensifier tubes are also sensitive in this range.
Short-wavelength infrared, SWIR	1.4-3 µm	0.4-0.9 eV	The absorption of electromagnetic radiation by water increases significantly at 1450 nm. The 1530-1560 nm range dominates the long-distance region.
Mid-wavelength infrared, MWIR	3-8 µm	150-400 meV	In this range, bodies heated to several hundred degrees Celsius begin to radiate. In this range, thermal heads homing of air defense systems and technical thermal imagers are sensitive.
Long-wavelength infrared, LWIR	8-15 µm	80-150 meV	In this range, bodies with temperatures around zero degrees Celsius begin to radiate. In this range, thermal imagers for night vision devices are sensitive.
Far-infrared, FIR	15 - 1000 µm	1.2-80 meV

CIE scheme

International Commission on Illumination International Commission on Illumination ) recommends the division of infrared radiation into the following three groups:

• IR-A: 700 nm - 1400 nm (0.7 µm - 1.4 µm)
• IR-B: 1400 nm - 3000 nm (1.4 µm - 3 µm)
• IR-C: 3000 nm - 1 mm (3 µm - 1000 µm)

ISO 20473 schema

thermal radiation

Thermal radiation or radiation is the transfer of energy from one body to another in the form of electromagnetic waves emitted by bodies due to their internal energy. Thermal radiation is mainly in the infrared region of the spectrum from 0.74 microns to 1000 microns. A distinctive feature of radiant heat transfer is that it can be carried out between bodies located not only in any medium, but also in vacuum. An example of thermal radiation is light from an incandescent lamp. The thermal radiation power of an object that meets the criteria of an absolutely black body is described by the Stefan-Boltzmann law. The ratio of the radiative and absorptive abilities of bodies is described by the law radiation Kirchhoff. Thermal radiation is one of the three elementary types of thermal energy transfer (in addition to thermal conductivity and convection). Equilibrium radiation is thermal radiation that is in thermodynamic equilibrium with matter.

Application

Night-vision device

There are several ways to visualize an invisible infrared image:

• Modern semiconductor video cameras are sensitive in the near infrared. To avoid color errors, ordinary household video cameras are equipped with a special filter that cuts off the IR image. Cameras for security systems, as a rule, do not have such a filter. However, at night there are no natural sources of near-IR, so without artificial illumination (for example, infrared LEDs), such cameras will not show anything.
• Image intensifier tube - a vacuum photoelectronic device that amplifies light in the visible spectrum and near infrared. It has high sensitivity and is able to give an image in very low light. They are historically the first night vision devices, widely used and currently in cheap night vision devices. Since they work only in the near IR, they, like semiconductor video cameras, require lighting.
• Bolometer - thermal sensor. Bolometers for technical vision systems and night vision devices are sensitive in the wavelength range of 3..14 microns (mid-IR), which corresponds to the radiation of bodies heated from 500 to -50 degrees Celsius. Thus, bolometric devices do not require external illumination, registering the radiation of the objects themselves and creating a picture of the temperature difference.

thermography

Infrared thermography, thermal image or thermal video is a scientific method for obtaining a thermogram - an image in infrared rays that shows a picture of the distribution of temperature fields. Thermographic cameras or thermal imagers detect radiation in the infrared range of the electromagnetic spectrum (approximately 900-14000 nanometers or 0.9-14 µm) and, based on this radiation, create images that allow you to determine overheated or supercooled places. Since infrared radiation is emitted by all objects that have a temperature, according to Planck's formula for black body radiation, thermography allows you to "see" the environment with or without visible light. The amount of radiation emitted by an object increases as its temperature rises, so thermography allows us to see differences in temperature. When we look through a thermal imager, warm objects are seen better than those cooled to ambient temperature; humans and warm-blooded animals are more easily visible in the environment, both during the day and at night. As a result, the promotion of the use of thermography can be attributed to the military and security services.

infrared homing

Infrared homing head - a homing head that works on the principle of capturing infrared waves emitted by a captured target. It is an optical-electronic device designed to identify a target against the surrounding background and issue a capture signal to an automatic sighting device (APU), as well as to measure and issue a signal of the angular velocity of the line of sight to the autopilot.

Infrared heater

Data transfer

The spread of infrared LEDs, lasers and photodiodes made it possible to create a wireless optical data transmission method based on them. In computer technology, it is usually used to connect computers with peripheral devices (IrDA interface). Unlike the radio channel, the infrared channel is insensitive to electromagnetic interference, and this allows it to be used in industrial conditions. The disadvantages of the infrared channel include the need for optical windows on the equipment, the correct relative orientation of devices, low transmission rates (usually does not exceed 5-10 Mbit / s, but when using infrared lasers, significantly higher rates are possible). In addition, secrecy of information transfer is not ensured. In line-of-sight conditions, an infrared channel can provide communication over distances of several kilometers, but it is most convenient for connecting computers located in the same room, where reflections from the walls of the room provide a stable and reliable connection. The most natural type of topology here is the "bus" (that is, the transmitted signal is simultaneously received by all subscribers). The infrared channel could not be widely used, it was replaced by the radio channel.

Thermal radiation is also used to receive warning signals.

Remote control

Infrared diodes and photodiodes are widely used in remote control panels, automation systems, security systems, some mobile phones (infrared port), etc. Infrared rays do not distract a person's attention due to their invisibility.

Interestingly, the infrared radiation of a household remote control is easily captured using a digital camera.

The medicine

The most widely used infrared radiation in medicine is found in various blood flow sensors (PPGs).

Widespread pulse rate (HR, HR - Heart Rate) and blood oxygen saturation (Sp02) meters use green (for pulse) and red and infrared (for SpO2) radiation LEDs.

Infrared laser radiation is used in the DLS (Digital Light Scattering) technique to determine the pulse rate and blood flow characteristics.

Infrared rays are used in physiotherapy.

Influence of long-wave infrared radiation:

• Stimulation and improvement of blood circulation. When exposed to long-wave infrared radiation on the skin, skin receptors are irritated and, due to the reaction of the hypothalamus, the smooth muscles of the blood vessels relax, as a result, the vessels dilate.
• Improvement of metabolic processes. The thermal effect of infrared radiation stimulates activity at the cellular level, improves the processes of neuroregulation and metabolism.

Food sterilization

With the help of infrared radiation, food products are sterilized for the purpose of disinfection.

food industry

A feature of the use of infrared radiation in the food industry is the possibility of penetration of an electromagnetic wave into such capillary-porous products as grain, cereals, flour, etc. to a depth of up to 7 mm. This value depends on the nature of the surface, structure, properties of the material and the frequency response of the radiation. An electromagnetic wave of a certain frequency range has not only a thermal, but also a biological effect on the product, it helps to accelerate biochemical transformations in biological polymers (