Learn more about infrared radiation. About infrared radiation

Infrared light is visually inaccessible to human vision. Meanwhile, long infrared waves are perceived by the human body as heat. Infrared light has some properties of visible light. Radiation of this form lends itself to focusing, is reflected and polarized. Theoretically, IR light is more interpreted as infrared radiation (IR). Space IR occupies the spectral range of electromagnetic radiation 700 nm - 1 mm. IR waves are longer than visible light and shorter than radio waves. Accordingly, IR frequencies are higher than microwave frequencies and lower than visible light frequencies. The IR frequency is limited to the range of 300 GHz - 400 THz.

Infrared waves were discovered by the British astronomer William Herschel. The discovery was registered in 1800. Using glass prisms in his experiments, the scientist in this way explored the possibility of dividing sunlight into separate components.

When William Herschel had to measure the temperature of individual flowers, he discovered a factor in the increase in temperature when successively passing through the following series:

violet,
blue,
greenery,
yolk,
orange,
red.

Wave and frequency range of IR radiation

Based on the wavelength, scientists conditionally divide infrared radiation into several spectral parts. However, there is no single definition of the boundaries of each individual part.

Scale of electromagnetic radiation: 1 - radio waves; 2 - microwaves; 3 - IR waves; 4 - visible light; 5 - ultraviolet; 6 - x-ray rays; 7 - gamma rays; B is the wavelength range; E - energy

Theoretically, three wave ranges are designated:

Near
Average
Further

The near infrared range is marked by wavelengths close to the end of the visible light spectrum. The approximate calculated wave segment is indicated here by the length: 750 - 1300 nm (0.75 - 1.3 microns). The radiation frequency is approximately 215-400 Hz. Short IR range will emit a minimum of heat.

Middle IR range (intermediate), covers wavelengths of 1300-3000 nm (1.3 - 3 microns). Frequencies are measured here in the range of 20-215 THz. The level of radiated heat is relatively low.

The far infrared range is closest to the microwave range. Alignment: 3-1000 microns. Frequency range 0.3-20 THz. This group consists of short wavelengths at the maximum frequency interval. This is where the maximum heat is emitted.

Application of infrared radiation

IR rays have been used in various fields. Among the most famous devices are thermal imagers, night vision equipment, etc. Communication and network equipment IR light is used in both wired and wireless operations.

An example of the operation of an electronic device - a thermal imager, the principle of which is based on the use of infrared radiation. And this is just one example out of many others.

Remote controls are equipped with a short-range IR communication system, where the signal is transmitted through IR LEDs. Example: common household appliances - TVs, air conditioners, players. Infrared light transmits data over fiber optic cable systems.

In addition, infrared radiation is actively used by research astronomy to study space. It is thanks to infrared radiation that it is possible to detect space objects that are invisible to the human eye.

Little-Known Facts About IR Light

Human eyes really cannot see infrared rays. But the skin of the human body is capable of “seeing” them, reacting to photons, and not just to thermal radiation.

The surface of the skin actually acts as an "eyeball". If you go outside on a sunny day, close your eyes and stretch your palms up to the sky, you can easily find the location of the sun.

In winter, in a room where the air temperature is 21-22ºС, being warmly dressed (sweater, trousers). In summer, in the same room, at the same temperature, people also feel comfortable, but in lighter clothes (shorts, T-shirt).

It is easy to explain this phenomenon: despite the same air temperature, the walls and ceiling of the room in summer emit more far-IR waves carried by sunlight (FIR - Far Infrared). Therefore, the human body at the same temperature, in the summer perceived more heat.

IR heat is reproduced by any living organism and inanimate object. On the screen of the thermal imager, this moment is noted more than clearly.

Pairs of people sleeping in the same bed are involuntarily transmitters and receivers of FIR waves in relation to each other. If a person is alone in bed, he acts as a transmitter of FIR waves, but no longer receives the same waves in return.

When people talk to each other, they involuntarily send and receive FIR wave vibrations from one another. Friendly (love) hugs also activate the transmission of FIR radiation between people.

How does nature perceive infrared light?

Humans are unable to see infrared light, but snakes of the viper or viper family (such as rattlesnakes) have sensory "pits" that are used to image in infrared light.

This property allows snakes to detect warm-blooded animals in complete darkness. Snakes with two sensory pits are thought to have some infrared depth perception.

Properties of the IR snake: 1, 2 - sensitive zones of the sensory cavity; 3 - membrane cavity; 4 - internal cavity; 5 - MG fiber; 6 - outer cavity

Fish successfully use Near Infrared (NIR) light to capture prey and navigate in water areas. This sense of NIR helps the fish navigate accurately in low light conditions, in the dark or in murky water.

Infrared radiation plays an important role in shaping the Earth's weather and climate, just like sunlight. The total mass of sunlight absorbed by the Earth, in an equal amount of IR radiation, must travel from the Earth back into space. Otherwise, global warming or global cooling is inevitable.

There is an obvious reason why the air cools quickly on a dry night. The low level of humidity and the absence of clouds in the sky open up a free path for infrared radiation. Infrared rays enter outer space faster and, accordingly, carry away heat faster.

A significant part of what comes to the Earth is infrared light. Any natural organism or object has a temperature, which means it releases infrared energy. Even objects that are a priori cold (such as ice cubes) emit infrared light.

Technical potential of the infrared zone

The technical potential of IR rays is limitless. Lots of examples. Infrared tracking (homing) is used in passive missile control systems. Electromagnetic radiation from the target, received in the infrared part of the spectrum, is used in this case.

Target tracking systems: 1, 4 - combustion chamber; 2, 6 - relatively long flame exhaust; 5 - cold flow bypassing the hot chamber; 3, 7 - assigned important IR signature

Weather satellites equipped with scanning radiometers produce thermal images, which then allow analytical methods to determine cloud heights and types, calculate land and surface water temperatures, and determine ocean surface features.

Infrared radiation is the most common way to remotely control various devices. Based on FIR technology, many products are being developed and produced. The Japanese excelled here. Here are just a few examples popular in Japan and around the world:

special pads and heaters FIR;
FIR plates to keep fish and vegetables fresh for a long time;
ceramic paper and ceramics FIR;
fabric FIR gloves, jackets, car seats;
hairdresser's FIR-dryer, which reduces damage to hair;

Infrared reflectography (art conservation) is used to study paintings, helping to reveal the underlying layers without destroying the structure. This technique helps to reveal the details hidden under the artist's drawing.

In this way, it is determined whether the current painting is an original work of art or just a professionally made copy. The changes associated with the restoration work on works of art are also determined.

IR rays: impact on human health

The beneficial effects of sunlight on human health have been scientifically proven. However, excessive exposure to solar radiation is potentially dangerous. Sunlight contains ultraviolet rays, the action of which burns the skin of the human body.

Infrared saunas of mass use are widespread in Japan and China. And the trend towards the development of this method of healing is only intensifying.

Meanwhile, far infrared provides all the health benefits of natural sunlight. This completely eliminates the dangerous effects of solar radiation.

By applying IR beam reproduction technology, full temperature control (), unlimited sunlight is achieved. But these are not all known facts about the benefits of infrared radiation:

Far infrared rays strengthen the cardiovascular system, stabilize heart rate, increase cardiac output, while reducing diastolic blood pressure.
The stimulation of cardiovascular function with far infrared light is an ideal way to maintain a normal cardiovascular system. There is an experience of American astronauts during a long space flight.
Far infrared IR rays with temperatures above 40°C weaken and eventually kill cancer cells. This fact is confirmed by the American Cancer Association and the National Cancer Institute.
Infrared saunas are often used in Japan and Korea (hyperthermia therapy or Waon therapy) for the treatment of cardiovascular diseases, especially chronic heart failure and peripheral arterial disease.
Research results published in the journal Neuropsychiatric Disease and Treatment show infrared rays as a "medical breakthrough" in the treatment of traumatic brain injury.
Infrared sauna is considered seven times more effective in removing heavy metals, cholesterol, alcohol, nicotine, ammonia, sulfuric acid and other toxins from the body.
Finally, FIR-therapy in Japan and China came out on top among the effective ways to treat asthma, bronchitis, colds, flu, sinusitis. It is noted that FIR-therapy removes inflammation, swelling, mucous blockages.

Infrared light and a lifespan of 200 years

Infrared (IR) rays are electromagnetic waves. The human eye is not able to perceive this radiation, but a person perceives it as thermal energy and feels it with all his skin. We are constantly surrounded by sources of infrared radiation, which differ in intensity and wavelength.

Should we be afraid of infrared rays, do they harm or benefit a person and what is their effect?

What is infrared radiation, its sources

As you know, the spectrum of solar radiation, perceived by the human eye as a visible color, is between violet waves (the shortest - 0.38 microns) and red (the longest - 0.76 microns). In addition to these waves, there are electromagnetic waves that are not available to the human eye - ultraviolet and infrared. "Ultra" means that they are below or, in other words, less than violet radiation. "Infra", respectively, - higher or more red radiation.

That is, IR radiation is electromagnetic waves that lie beyond the red color range, the length of which is greater than that of visible red radiation. While studying electromagnetic radiation, the German astronomer William Herschel discovered the invisible waves that caused the temperature of the thermometer to rise and called them infrared heat radiation.

The most powerful natural source of thermal radiation is the Sun. Of all the rays emitted by the sun, 58% falls precisely on the share of infrared. Artificial sources are all electric heaters that convert electricity into heat, as well as any objects whose temperature is above the absolute zero mark - 273 ° C.

Properties of infrared radiation

IR radiation has the same nature and properties as ordinary light, only a longer wavelength. Light waves visible to the eye, reaching objects, are reflected, refracted in a certain way, and a person sees the reflection of the object in a wide range of colors. And infrared rays, reaching an object, are absorbed by it, releasing energy and heating this object. We do not see infrared radiation, but we feel it as heat.

In other words, if the Sun did not emit a wide spectrum of long-wave infrared rays, a person would only see sunlight, but not feel its warmth.

It is difficult to imagine life on Earth without solar heat.

Some of it is absorbed by the atmosphere, and the waves reaching us are divided into:

Short - the length lies in the range of 0.74 microns - 2.5 microns, and exude their objects heated to a temperature of more than 800 ° C;

Medium - from 2.5 microns to 50 microns, heating t from 300 to 600os;

Long - the widest range from 50 microns to 2000 microns (2 mm), t up to 300 ° C.

The properties of infrared radiation, its benefits and harms to the human body, are determined by the source of radiation - the higher the temperature of the emitter, the more intense the waves and the deeper their penetrating ability, the degree of impact on any living organisms. Studies conducted on the cellular material of plants and animals have discovered a number of useful properties of infrared rays, which have found wide application in medicine.

The benefits of infrared radiation for humans, use in medicine

Medical studies have proven that infrared rays in the long range are not only safe, but also very useful for humans. They activate blood flow and improve metabolic processes, inhibit the development of bacteria and promote rapid healing of wounds after surgical interventions. They contribute to the development of immunity against toxic chemicals and gamma radiation, stimulate the elimination of toxins, toxins through sweat and urine and lower cholesterol.

Particularly effective are the rays of 9.6 microns in length, which contribute to the regeneration (recovery) and healing of organs and systems of the human body.

In folk medicine, from time immemorial, treatment with heated clay, sand or salt has been used - these are vivid examples of the beneficial effects of thermal infrared rays on humans.

Modern medicine for the treatment of a number of diseases has learned to use the beneficial properties:

With the help of infrared radiation, it is possible to treat bone fractures, pathological changes in the joints, and relieve muscle pain;

IR rays have a positive effect in the treatment of paralyzed patients;

Quickly heal wounds (postoperative and others), relieve pain;

By stimulating blood circulation, they help to normalize blood pressure;

Improve blood circulation in the brain and memory;

Remove salts of heavy metals from the body;

They have a pronounced antimicrobial, anti-inflammatory and antifungal effect;

Strengthen the immune system.

Bronchial asthma, pneumonia, osteochondrosis, arthritis, urolithiasis, bedsores, ulcers, sciatica, frostbite, diseases of the digestive system - this is not a complete list of pathologies for the treatment of which the positive effect of infrared radiation is used.

Heating residential premises with the help of infrared radiation devices contributes to air ionization, fights allergies, destroys bacteria, mold fungi, improves the condition of the skin due to the activation of blood circulation. When purchasing a heater, it is imperative to choose long-wave devices.

Other applications

The property of objects to radiate heat waves has found application in various fields of human activity. For example, with the help of special thermographic cameras capable of capturing thermal radiation, any objects can be seen and recognized in absolute darkness. Thermographic cameras are widely used in the military and industry to detect invisible objects.

In meteorology and astrology, IR rays are used to determine distances to objects, clouds, water surface temperatures, etc. Infrared telescopes allow you to study space objects that are inaccessible to vision through conventional instruments.

Science does not stand still and the number of IR devices and their applications is constantly growing.

Harm

A person, like any body, emits medium and long infrared waves, which lie in the range from 2.5 microns to 20-25 microns, so it is the waves of this length that are completely safe for humans. Short waves are able to penetrate deeply into human tissues, causing heating of internal organs.

Short-wave infrared radiation is not only harmful, but also very dangerous for humans, especially for the visual organs.

Solar thermal shock, provoked by short waves, occurs when the brain is heated by only 1C. Its symptoms are:

severe dizziness;

Nausea;

Increased heart rate;

Loss of consciousness.

Metallurgists and steelmakers, who are constantly exposed to thermal effects of short infrared rays, are more likely to suffer from diseases of the cardiovascular system, have weakened immunity, and are more likely to suffer from colds.

To avoid the harmful effects of infrared radiation, it is necessary to take protective measures and limit the time spent under dangerous rays. But the benefits of thermal solar radiation for life on our planet are undeniable!

There are natural phenomena that are invisible to the human eye, although we feel the power of their action. They are able to exert no less influence than visible processes. We cannot see infrared rays, but we can feel their warmth. The action of infrared radiation is beneficial for living organisms on Earth and plays an important role in the development of life. All living things are under the influence of infrared light.

The peculiarity of infrared radiation is that without it, various diseases appear in the human body, and aging accelerates. But in this case, the line between the benefits and harms of infrared radiation for humans is thin. Therefore, it is important to know how not to step over it and what to do if infrared rays have led to negative consequences.

What is infrared radiation?

Studying the Sun in 1800, the English scientist W. Herschel measured the temperature of various parts of the visible spectrum. He found that behind the saturated red color is the highest point of heat. Then the concept of infrared radiation (IR radiation) appeared in science.

Infra-red rays are invisible to the naked eye, but are felt by the skin as heat. They refer to electromagnetic radiation that lies between the red end of visible light and microwave radio emission. IR radiation is also called thermal radiation.

It is emitted by atoms, which have excess energy, and ions. Every body with a temperature above zero is a source of infrared radiation. The sun is a well-known natural source of infrared rays.

The wavelength in IR radiation depends on the heating temperature. The highest temperature is for short waves with high radiation intensity. The range of infrared rays is wide. It is divided into varieties:

short waves - temperatures above 800 degrees Celsius,
medium waves - up to 600 degrees Celsius,
long waves - up to 300 degrees Celsius.

The effect of infrared radiation on the human body is determined by the length of these waves, as well as the time period of exposure.

The benefits of infrared rays for humans

Long-wave infrared rays are beneficial for human health. It is often used in medicine, in particular in physiotherapy procedures, with which blood circulation, metabolism and neuroregulation can be improved.

The positive effect of infrared radiation on the human body is as follows:

improves memory and brain function,
normalizes blood pressure,
hormonal balance is normalized,
salts, toxins and heavy metals are removed,
stops the reproduction of fungi and harmful microorganisms,
the water-salt balance is restored,
pain relief occurs
an anti-inflammatory process takes place
cancer cells are suppressed
the results of radioactive radiation are neutralized,
increased insulin in diabetic patients,
dystrophy is cured
psoriasis goes away
immunity is strengthened.

Heating, which uses infrared rays, kills harmful bacteria and helps strengthen the immune system. Air ionization protects against allergic manifestations. Long waves of infrared heat have a calming effect on fatigue, irritability, stress, promote wound healing, and lead to recovery from influenza.

Harm from infrared radiation

Despite the beneficial properties of infrared rays, they also have contraindications. Short waves are especially dangerous. Their harm can be expressed in redness of the skin and burns, heat stroke and dermatitis, the appearance of convulsions and a violation of the water-salt balance. Shortwave for the mucous membrane of the eyes. It not only dries it out, but can also cause serious eye ailments.

The short-wave effect on the human body is expressed in certain signs:

dizziness,
nausea,
darkening in the eyes
heart palpitations,
impaired coordination of movements,
loss of consciousness.

Such symptoms occur if the temperature of the brain rises even by one degree Celsius. With an increase of two degrees Celsius, meningitis and encephalitis appear.

Contraindications to the use of infrared rays are:

blood diseases,
bleeding,
inflammatory processes,
acute purulent manifestations,
malignant tumors.

Where is infrared radiation found?

Infrared radiation is used in various areas of human activity. These include: thermography, astronomy, medicine, food industry and others.

IR emitters can be different devices:

homing head in the sighting device,
night-vision devices,
physiotherapy equipment,
heating systems,
heaters,
remote control devices.

Any heated body is a source of infrared radiation.

As for heaters, when buying them, you should pay attention to the nature of the radiation of the device, which is usually indicated in the technical data sheet. If the spiral that releases heat has heat-insulating protection, this means that the action of its long waves will have a positive effect on the body. If the heating element is not insulated, then the device emits short waves that cause health problems.

Important! If the device emits short-wave radiation, do not stay near it for a long time and keep it at a distance from you.

Helping a Heat Stroke Victim

Exposure to infrared heat can lead to heatstroke. In this case, it is necessary to provide the victim with the following measures of assistance:

put it in a cool place
free from tight clothing,
apply cold to the neck, head, heart area, spine and inguinal perineum,
wrap a person in a sheet soaked in cold water,
turn on the fan and direct it to the affected air,
often drink cold
perform artificial respiration, if necessary,
call an ambulance.

Conclusion

Understanding the nature of infrared rays, we are aware of their indispensability for the life and normal functioning of the human body. Despite the benefits of infrared radiation for humans, it can also cause irreparable harm if it operates in the shortwave range. Therefore, be careful when getting under the influence of infrared light. Consider the contraindications that are available to him. And if heatstroke happened to someone around you, provide him with the necessary assistance.

INFRARED RADIATION (IR radiation, IR rays), electromagnetic radiation with wavelengths λ from about 0.74 μm to about 1-2 mm, that is, radiation occupying the spectral region between the red end of visible radiation and shortwave (submillimeter) radio radiation. Infrared radiation refers to optical radiation, but unlike visible radiation, it is not perceived by the human eye. Interacting with the surface of bodies, it heats them up, so it is often called thermal radiation. Conventionally, the region of infrared radiation is divided into near (λ = 0.74-2.5 microns), middle (2.5-50 microns) and far (50-2000 microns). Infrared radiation was discovered by W. Herschel (1800) and independently by W. Wollaston (1802).

Infrared spectra can be line (atomic spectra), continuous (condensed matter spectra) or striped (molecular spectra). Optical properties (transmission, reflection, refraction, etc.) of substances in infrared radiation, as a rule, differ significantly from the corresponding properties in visible or ultraviolet radiation. Many substances that are transparent to visible light are opaque to infrared radiation of certain wavelengths, and vice versa. Thus, a layer of water several centimeters thick is opaque to infrared radiation with λ > 1 µm, so water is often used as a heat-shielding filter. Plates of Ge and Si, opaque to visible radiation, are transparent to infrared radiation of certain wavelengths, black paper is transparent in the far infrared region (such substances are used as light filters when infrared radiation is isolated).

The reflectivity of most metals in infrared radiation is much higher than in visible radiation, and increases with increasing wavelength (see Metal Optics). Thus, the reflection of Al, Au, Ag, Cu surfaces of infrared radiation with λ = 10 μm reaches 98%. Liquid and solid non-metallic substances have a selective (depending on the wavelength) reflection of infrared radiation, the position of the maxima of which depends on their chemical composition.

Passing through the earth's atmosphere, infrared radiation is attenuated due to scattering and absorption by air atoms and molecules. Nitrogen and oxygen do not absorb infrared radiation and weaken it only as a result of scattering, which is much less for infrared radiation than for visible light. Molecules H 2 O, O 2 , O 3 , etc., present in the atmosphere, selectively (selectively) absorb infrared radiation, and the infrared radiation of water vapor is especially strongly absorbed. H 2 O absorption bands are observed in the entire IR region of the spectrum, and CO 2 bands - in its middle part. In the surface layers of the atmosphere there are only a small number of "transparency windows" for infrared radiation. The presence in the atmosphere of particles of smoke, dust, small drops of water leads to an additional attenuation of infrared radiation as a result of its scattering on these particles. At small particle sizes, infrared radiation is scattered less than visible radiation, which is used in infrared photography.

Sources of infrared radiation. A powerful natural source of infrared radiation is the Sun, about 50% of its radiation lies in the infrared region. Infrared radiation accounts for 70 to 80% of the radiation energy of incandescent lamps; it is emitted by an electric arc and various gas-discharge lamps, all types of electric space heaters. In scientific research, the sources of infrared radiation are tungsten tape lamps, a Nernst pin, a globe, high-pressure mercury lamps, etc. The radiation of some types of lasers also lies in the IR region of the spectrum (for example, the wavelength of neodymium glass lasers is 1.06 μm, helium-neon lasers - 1.15 and 3.39 microns, CO 2 lasers - 10.6 microns).

Receivers of infrared radiation are based on the conversion of radiation energy into other types of energy available for measurement. In thermal receivers, the absorbed infrared radiation causes an increase in the temperature of the temperature-sensitive element, which is recorded. In photoelectric receivers, the absorption of infrared radiation leads to the appearance or change in the strength of an electric current or voltage. Photoelectric receivers (unlike thermal ones) are selective, that is, they are sensitive only to radiation from a certain region of the spectrum. Photo registration of infrared radiation is carried out with the help of special photographic emulsions, however, they are sensitive to it only for wavelengths up to 1.2 microns.

The use of infrared radiation. IR radiation is widely used in scientific research and for solving various practical problems. The emission and absorption spectra of molecules and solids lie in the IR region, they are studied in infrared spectroscopy, in structural problems, and are also used in qualitative and quantitative spectral analysis. In the far IR region lies the radiation that occurs during transitions between the Zeeman sublevels of atoms, the IR spectra of atoms make it possible to study the structure of their electron shells. Photographs of the same object taken in the visible and infrared ranges, due to the difference in the coefficients of reflection, transmission and scattering, can vary significantly; In IR photography, you can see details that are not visible in normal photography.

In industry, infrared radiation is used for drying and heating materials and products, in everyday life - for space heating. On the basis of photocathodes sensitive to infrared radiation, electron-optical converters have been created, in which the infrared image of an object, invisible to the eye, is converted into a visible one. On the basis of such converters, various night vision devices (binoculars, sights, etc.) are built, which make it possible to detect objects in complete darkness, to observe and aim, irradiating them with infrared radiation from special sources. With the help of highly sensitive infrared receivers, objects are located by their own infrared radiation and homing systems for projectiles and missiles are created. IR locators and IR rangefinders allow you to detect in the dark objects whose temperature is higher than the ambient temperature, and measure the distance to them. The powerful radiation of infrared lasers is used in scientific research, as well as for terrestrial and space communications, for laser sounding of the atmosphere, etc. Infrared radiation is used to reproduce the meter standard.

Lit .: Schreiber G. Infrared rays in electronics. M., 2003; Tarasov VV, Yakushenkov Yu. G. Infrared systems of "looking" type. M., 2004.

Translation by Dmitry Viktorov

Abbreviation: IR radiation
Definition: Invisible radiation with wavelengths from approximately 750 nm to 1 mm.

Infrared radiation- this is radiation with a wavelength greater than 700 - 800 nm, the upper limit of the visible wavelength range. This limit does not determine how the sensitivity of the eye to visible radiation in a given spectral region decreases.

Even though the sensitivity of the eye to visible light, for example at 700 nm, is already very weak, the emission from some laser diodes with wavelengths above 750 nm can still be seen if the emission is strong enough. Such radiation can be harmful to the eyes, even if it is not perceived as very bright. The upper limit of the infrared region of the spectrum in terms of wavelength is also not clearly defined, usually around 1 µm.

In order to "see" in infrared light, night vision goggles are used.

For areas of the infrared spectrum, the following classification is used:

- near infrared (also called IR-A) is ~ from 700 to 1400 nm. Lasers emitting in this wavelength range are especially dangerous to the eyes, since near infrared radiation is transmitted and focused on the sensitive retina in the same way as visible light, while at the same time it does not cause a protective blink reflex. Appropriate eye protection is required.
- shortwave infrared (IR-B) extends from 1.4 to 3 µm. This range is relatively safe for the eyes, since such radiation will be absorbed by the substance of the eye before it can reach the retina. Erbium-doped fiber amplifiers for optical fiber communications operate in this range.
- mid-wave infrared range (IR-C) from 3 to 8 µm. The atmosphere experiences strong absorption in this range. There are many absorption lines, for example for carbon dioxide (CO2) and water vapor (H2O). Many gases have strong and characteristic mid-IR absorption lines, making this region of the spectrum of interest for highly sensitive gas spectroscopy.
- longwave IR varies from 8 to 15 µm, following the far infrared, which extends up to 1 mm, in the literature it sometimes starts as early as 8 µm. The long-wave IR region of the spectrum is used for thermal imaging.

However, it should be noted that the definitions of these terms vary significantly in the literature. Most glasses are transparent to near-infrared radiation, but they strongly absorb radiation of long wavelengths, while photons of this radiation can be directly converted into phonons. For silica glass used in silica fibers, strong absorption occurs after 2 µm.

Infrared radiation is also called thermal radiation, since thermal radiation from heated bodies is mostly in the infrared region. Even at room temperature and below, bodies emit significant amounts of mid- and far-infrared radiation, which can be used for thermal imaging.
For example, infrared images of a house heated in winter can reveal heat leaks (eg at windows, the roof, or in poorly insulated walls behind radiators) and thus help to take effective improvement measures.

According to the materials of the Internet portal