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Near infrared spectrum. Basic properties of infrared radiation

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

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

When William Herschel had to take his temperature individual colors, a factor of temperature increase was discovered during the sequential passage of the following series:

  • violet,
  • blue,
  • green,
  • yolk,
  • orange,
  • red.

Wave and frequency range of IR radiation

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

Electromagnetic radiation scale: 1 - radio waves; 2 - microwaves; 3 - IR waves; 4 - visible light; 5 - ultraviolet; 6 — x-ray rays; 7 - gamma rays; B - wavelength range; E - energy

Theoretically, three wave ranges are designated:

  1. Near
  2. Average
  3. Further

The near-infrared range is marked by wavelengths approaching 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 µm). The radiation frequency is approximately 215-400 Hz. Short IR wavelengths will emit minimal heat.

Mid-IR range (intermediate), covers wavelengths 1300-3000 nm (1.3 - 3 µm). Frequencies here are measured 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. Layout: 3-1000 microns. Frequency range 0.3-20 THz. This group consists short lengths waves at the maximum frequency range. This is where maximum heat is emitted.

Applications of infrared radiation

IR rays have found application in various fields. Among the most well-known devices are thermal imagers, night vision equipment, etc. Communications and networking equipment uses IR light as part of wired and wireless operations.


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

Remotes remote control 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 for space exploration. It is thanks to infrared radiation that it is possible to detect space objects 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, which reacts to photons, and not just to thermal radiation, is capable of “seeing” them.

The surface of the skin actually protrudes " eyeball" If you go outside on a sunny day, close your eyes and stretch your palms 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 the summer, in the same room, at the same temperature, people also feel comfortable, but in lighter clothes (shorts, T-shirt).

This phenomenon is easy to explain: despite the same air temperature, the walls and ceiling of the room in summer radiate more far infrared waves carried sunlight(FIR - Far Infrared). Therefore, the human body, at the same temperatures, perceives more heat in summer.


IR heat is reproduced by any living organism and inanimate object. This moment is noted more than clearly on the thermal imager screen

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 response.

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

How does nature perceive IR light?

Humans cannot see infrared light, but snakes of the viper family (such as rattlers) have sensory cavities that are used to produce images in infrared light.

This property allows snakes to detect warm-blooded animals in complete darkness. Snakes, with two sensory cavities, are scientifically hypothesized 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 - external cavity

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

Infrared radiation plays important role to shape the Earth's weather and climate, just like sunlight. The total mass of sunlight absorbed by the Earth, in equal amounts of infrared radiation, must move from the Earth back into space. Otherwise it's inevitable global warming or global cooling.

There is an obvious reason why the air cools quickly on a dry night. Low level humidity and lack of clouds in the sky open clear path IR radiation. Infrared rays come out faster outer space and, accordingly, remove heat faster.

A significant part coming to the Earth is infrared light. Any natural organism or the object has a temperature, which means it emits IR energy. Even objects that are a priori cold (for example, ice cubes) emit infrared light.

Technical potential of the infrared zone

The technical potential of infrared rays is limitless. There are plenty 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 enable analytical techniques to determine cloud heights and types, calculate land temperatures and surface waters, determine the features of the ocean surface.

Infrared radiation is the most common way to remotely control various devices. Many products are developed and produced based on FIR technology. The Japanese especially distinguished themselves here. Here are just a few examples that are popular in Japan and around the world:

  • special linings and FIR heaters;
  • FIR plates for keeping fish and vegetables fresh for a long time;
  • ceramic paper and FIR ceramics;
  • fabric FIR gloves, jackets, car seats;
  • hairdressing FIR hair dryer that reduces hair damage;

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

In this way it is determined whether the current picture is original a work of art or just a professionally made copy. Changes associated with restoration work on works of art are also identified.

IR rays: impact on human health

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


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

Far-wave infrared, meanwhile, provides all the health benefits of natural sunlight. This completely eliminates dangerous influence solar radiation.

By using infrared ray reproduction technology, complete temperature control () and unlimited sunlight are achieved. But that's not all known facts benefits of infrared radiation:

  • Far infrared rays strengthen cordially- vascular system, stabilize heart rate, increase cardiac output, while reducing diastolic blood pressure.
  • Stimulation of cardiovascular function infrared light long range - perfect way maintaining a normal cardiovascular system. There is experience of American astronauts during a long space flight.
  • Far infrared IR rays with temperatures above 40°C weaken and ultimately kill cancer cells. This fact has been confirmed by the American Cancer Association and National Institute cancer.
  • Infrared saunas are often used in Japan and Korea (hyperthermia therapy or Waon therapy) to treat cardiovascular diseases, especially chronic heart failure and peripheral arterial disease.
  • Research findings published in the journal Neuropsychiatric Disease and Treatment highlight infrared rays as a "medical breakthrough" in the treatment of traumatic brain injuries.
  • An infrared sauna is said to be 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 effective ways treatment of asthma, bronchitis, colds, flu, sinusitis. It has been noted that FIR therapy removes inflammation, swelling, and mucous blockages.

Infrared light and lifespan of 200 years

There are different sources infrared radiation. They are currently in household appliances, automation and security systems, and are also used for drying industrial products. Infrared light sources, when used correctly, do not affect the human body, which is why the products are very popular.

History of discovery

For many centuries, outstanding minds have been studying the nature and action of light.

Infrared light was discovered in the early 19th century through the research of astronomer W. Herschel. Its essence was to study the heating abilities of various solar areas. The scientist brought a thermometer to them and monitored the increase in temperature. This process was observed when the device touched the red border. V. Herschel concluded that there is a certain radiation that cannot be seen visually, but can be determined using a thermometer.

Infrared rays: application

They are widespread in human life and have found their application in various fields:

  • Military affairs. Modern missiles and warheads, capable of independently aiming at a target, are equipped with which are the result of the use of infrared radiation.
  • Thermography. Infrared radiation is used to study overheated or supercooled areas. Infrared images are also used in astronomy to detect celestial bodies.
  • Life The operation of which is aimed at heating interior items and walls has gained great popularity. They then release heat into the space.
  • Remote control. All existing remote controls for TV, furnaces, air conditioners, etc. equipped with infrared rays.
  • In medicine, infrared rays are used for treatment and prevention. various diseases.

Let's look at where these elements are used.

Infrared gas burners

An infrared burner is used to heat various rooms.

At first it was used for greenhouses, garages (i.e. non-residential premises). However modern technologies allowed to use it even in apartments. Popularly, such a burner is called a solar device, since when turned on, the working surface of the equipment resembles sunlight. Over time, such devices replaced oil heaters and convectors.

Main features

An infrared burner differs from other devices in its heating method. Heat transfer is carried out by means that are not noticeable to humans. This feature allows heat to penetrate not only into the air, but also onto interior items, which subsequently also increase the temperature in the room. The infrared emitter does not dry out the air, because the rays are primarily directed at interior items and walls. In the future, heat will be transferred from walls or objects directly to the space of the room, and the process occurs in a few minutes.

Positive aspects

The main advantage of such devices is quick and easy heating of the room. For example, it will take 20 minutes to heat a cold room to a temperature of +24ºС. During the process, there is no air movement, which contributes to the formation of dust and large contaminants. Therefore, an infrared emitter is installed indoors by those people who have allergies.

In addition, infrared rays, when hitting a surface with dust, do not cause it to burn, and, as a result, there is no smell of burnt dust. The quality of heating and durability of the device depends on the heating element. Such devices use a ceramic type.

Price

The price of such devices is quite low and accessible to all segments of the population. For example, a gas burner costs from 800 rubles. A whole stove can be purchased for 4,000 rubles.

Sauna

What is an infrared cabin? This is a special room that is built from natural types of wood (for example, cedar). Infrared emitters are installed in it, acting on the tree.

During heating, phytoncides are released - useful components that prevent the development or appearance of fungi and bacteria.

Such an infrared cabin is popularly called a sauna. The air temperature inside the room reaches 45ºС, so it is quite comfortable to be in it. This temperature allows you to warm up human body evenly and deeply. Therefore, heat does not affect the cardiovascular system. During the procedure, accumulated toxins and waste are removed, metabolism in the body is accelerated (due to the rapid movement of blood), and tissues are also enriched with oxygen. However, sweating is not the main property infrared sauna. It is aimed at improving well-being.

Impact on humans

Such premises have a beneficial effect on the human body. During the procedure, all muscles, tissues and bones are warmed up. Accelerating blood circulation affects metabolism, which helps saturate muscles and tissues with oxygen. In addition, the infrared cabin is visited to prevent various diseases. Most people leave only positive reviews.

Negative effects of infrared radiation

Sources of infrared radiation can cause not only positive impact on the body, but also harm it.

With prolonged exposure to rays, the capillaries expand, which leads to redness or burns. Special harm sources of infrared radiation damage the organs of vision - this leads to the formation of cataracts. In some cases, a person experiences seizures.

Short rays affect the human body, causing a deterioration in the brain's temperature by several degrees: darkening of the eyes, dizziness, nausea. A further increase in temperature can lead to the formation of meningitis.

Deterioration or improvement of the condition occurs due to intensity electromagnetic field. It is characterized by temperature and distance to the source of thermal energy radiation.

Long waves of infrared radiation play a special role in various life processes. Short ones have a greater effect on the human body.

How to prevent the harmful effects of infrared rays?

As mentioned earlier, short-term thermal radiation has a negative effect on the human body. Let's look at examples in which IR radiation is dangerous.

Today, infrared heaters that emit temperatures above 100ºC can be harmful to health. Among them are the following:

  • Industrial equipment emitting radiant energy. To prevent negative impact, special clothing and heat-protective elements should be used, and preventive measures among working personnel.
  • Infrared device. The most famous heater is the stove. However, it has long gone out of use. Increasingly, electric infrared heaters are being used in apartments, country houses and cottages. Its design includes a heating element (in the form of a spiral), which is protected by a special heat-insulating material. Such exposure to rays does not harm the human body. The air in the heated zone is not dried. You can heat the room in 30 minutes. First, infrared radiation heats objects, and then they heat the entire apartment.

Infrared radiation is widely used in various fields, from industrial to medicine.

However, they should be handled with care, as the rays can have a negative effect on humans. It all depends on the wavelength and distance to the heating device.

So, we found out what sources of infrared radiation exist.

Infrared (IR) radiation is a type of electromagnetic radiation that occupies the spectral range between visible red light (INFRAred: BELOW red) and shortwave radio waves. These rays create heat and are scientifically known as thermal waves. These rays create heat and are scientifically known as thermal waves.

All heated bodies emit infrared radiation, including the human body and the Sun, which in this way warms our planet, giving life to all life on it. The warmth that we feel from a fire near a fire or fireplace, a heater or warm asphalt is all a consequence of infrared rays.

The entire spectrum of infrared radiation is usually divided into three main ranges, differing in wavelength:

  • Short wavelength, with wavelength λ = 0.74-2.5 µm;
  • Medium wave, with wavelength λ = 2.5-50 µm;
  • Long wavelength, with wavelength λ = 50-2000 µm.

Near or short-wave infrared rays are not hot at all; in fact, we don’t even feel them. These waves are used, for example, in TV remote controls, automation systems, security systems, etc. Their frequency is higher, and accordingly their energy is higher than that of far (long) infrared rays. But not at such a level as to harm the body. Heat begins to be created at mid-infrared wavelengths, and we already feel their energy. Infrared radiation is also called “thermal” radiation, because radiation from heated objects is perceived by the human skin as a sensation of heat. 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. For example, a source with a wavelength of 1.1 microns corresponds to molten metal, and a source with a wavelength of 3.4 microns corresponds to metal at the end of rolling and forging.

Of interest to us is the spectrum with a wavelength of 5-20 microns, since it is in this range that more than 90% of the radiation produced by infrared heating systems occurs, with a radiation peak of 10 microns. It is very important that it is at this frequency that the human body itself emits infrared waves of 9.4 microns. Thus, any radiation at a given frequency is perceived by the human body as related and has a beneficial and, even moreover, healing effect on it.

With such exposure to infrared radiation on the body, the effect of “resonance absorption” occurs, which is characterized by the body’s active absorption of external energy. As a result, one can observe an increase in a person’s hemoglobin level, an increase in the activity of enzymes and estrogens, and, in general, a stimulation of a person’s vital activity.

The effect of infrared radiation on the surface of the human body, as we have already said, is useful and, on top of that, pleasant. Remember the first sunny days at the beginning of spring, when after a long and cloudy winter the sun finally came out! You feel how it pleasantly envelops the illuminated area of ​​your skin, face, palms. I no longer want to wear gloves and a hat, despite the temperature being quite low compared to the “comfortable” one. But as soon as a small cloud appears, we immediately experience noticeable discomfort from the interruption of such a pleasant sensation. This is the very radiation that we so lacked throughout the winter, when the Sun was absent for a long time, and we, willy-nilly, carried out our “infrared post”.

As a result of exposure to infrared radiation, you can observe:

  • Acceleration of metabolism in the body;
  • Restoration of skin tissue;
  • Slowing down the aging process;
  • Removing excess fat from the body;
  • Release of human motor energy;
  • Increasing the body's antimicrobial resistance;
  • Activation of plant growth

and much much more. Moreover, infrared irradiation is used in physiotherapy to treat many diseases, including cancer, as it promotes the expansion of capillaries, stimulates blood flow in the vessels, improves immunity and produces a general therapeutic effect.

And this is not at all surprising, because this radiation is given to us by nature as a way of transmitting heat and life to all living things that need this warmth and comfort, bypassing empty space and air as intermediaries.

Infrared wavelength

A lot of unreliable (and sometimes downright false) information is being distributed on the Internet regarding the penetration of infrared radiation into the human body. Typically, such information is disseminated by sellers of cabins with carbon (film) heaters, inventing various pseudoscientific terms: “resonant absorption”, “Rays of Life”, etc. To clarify this issue, we provide a description of the interaction of infrared radiation with living tissue based on scientific literature that is accepted throughout the world.

Interaction of IR radiation with living tissues

The infrared region of the spectrum, according to international classification, are divided into near IR-A (from 0.76 to 1.5 µm), medium IR-B (1.5 - 3 µm) and far IR-C (over 3 µm).

From the point of view of human physiology, near-infrared rays in the area and in the proportions in which we usually receive them from the Sun through the atmosphere are not only useful, but also necessary. Near infrared rays (up to 1.5 microns) are absorbed in depth skin, while infrared rays with a longer wavelength are absorbed already on their surface.

Indeed, the skin is transparent to infrared radiation with a wavelength of up to 1.5 microns. Then it becomes relatively opaque and is characterized by a rather complex absorption spectrum. The skin should be considered as a complex consisting of the epidermis, the transparency of which can vary depending on the condition, pigments, intercellular tissues, subcutaneous fat etc. Possessing great hygroscopicity and being rich in blood vessels, the skin complex is a physiological screen, the transparency of which for infrared rays depends on the wavelength. It should be assumed that for infrared rays with a wavelength of more than 5 microns, the skin is completely opaque.

Considering physiological characteristics human, therapists divide the infrared range into 3 categories:

    wavelength more than 5 microns - radiation absorbed on the surface of the skin;

    wavelength 1.5 ÷ 5 µm - radiation absorbed by the epidermis and connective tissue layer of the skin;

    wavelength 0.76 ÷ 1.5 µm - radiation penetrating deep into the skin;

When it is necessary to influence the surface of the skin, mucous membrane, and vascular system, long-wavelength ranges are used. For impact in depth, for example on lymphatic system or muscle tissue, use infrared radiation with a wavelength of 0.76-1.5 microns. The energy absorbed by the skin is converted into heat. The tolerable skin temperature is 43.8°C for the short-wave radiation range, and reaches 45.5°C for the long-wave radiation range, which indicates the different effects of these two areas of radiation.

The human body, like any heated body, emits infrared radiation. Any biological object (in particular a person) is complex system different molecules that have their own emission spectra, therefore total radiation human radiation will differ significantly from the radiation of a completely black body at the same temperature. This emission occurs in the range between 2 and 14 µm with a maximum at 6 µm.

Important! For effective and volumetric heating of the human body, it is necessary to irradiate it with infrared radiation with a wavelength in the range of 0.76 - 3 microns, only in this case the maximum penetration of IR radiation will be observed. Infrared waves with a wavelength of more than 5 microns do not penetrate the human body, but are absorbed by the upper layers of the skin.

For real biological objects, Kirchhoff's law not executed, i.e. absorption spectra and emission spectra are different. The following graphs show the absorption spectra for water and human organ tissue depending on the wavelength. Note that the fabric human body consists of 98% water and this fact explains the similarity of absorption characteristics.

We specifically present several graphs from various primary sources in order to exclude any speculation on the topic of absorption of IR radiation. As you can see of these graphs, the greatest penetration is observed in the range from 0.7 to 3 µm and this range is called the “therapeutic transparency window”. Only radiation from this range can penetrate to a depth of 4 cm. At other wavelengths, infrared radiation is absorbed by the upper layers of the skin and cannot penetrate deep into the human body.

Schedule Source

"LOW REACTIVE-LEVEL LASER THERAPY PRACTICAL APPLICATION" T. Ohshiro (1988),

International Labor Organization, "Encyclopedia of Occupational Safety and Health", 2nd ed., 1988




"Biophysical foundations of physiotherapy", G.N. Ponomarenko, I.I. Turkovsky, Moscow, "Medicine", 2006, pp. 17-18., textbook for universities

In 1800, scientist William Herschel announced his discovery at a meeting of the Royal Society of London. He measured temperatures outside the spectrum and discovered invisible rays with great heating power. He carried out the experiment using telescope filters. He noticed that they absorb light and heat to varying degrees sun rays.

After 30 years, the existence of invisible rays located beyond the red part of the visible solar spectrum was indisputably proven. The French Becquerel called this radiation infrared.

Properties of IR radiation

The spectrum of infrared radiation consists of individual lines and bands. But it can also be continuous. It all depends on the source of the IR rays. In other words, what matters is the kinetic energy or temperature of an atom or molecule. Any element of the periodic table at different temperatures has various characteristics.

For example, infrared spectra excited atoms due to the relative state of rest of the nucleus ligament, they will have strictly line IR spectra. And excited molecules are striped and randomly located. Everything depends not only on the mechanism of superposition of the own linear spectra of each atom. But also from the interaction of these atoms with each other.

As the temperature rises, the spectral characteristics of the body change. Thus, heated solids and liquids emit a continuous infrared spectrum. At temperatures below 300°C, the radiation of heated solid entirely located in the infrared region. Both the study of IR waves and their applications depend on the temperature range. the most important properties.

The main properties of IR rays are absorption and further heating of bodies. The principle of heat transfer by infrared heaters differs from the principles of convection or conduction. Being in a flow of hot gases, an object loses some amount of heat as long as its temperature is lower than the temperature of the heated gas.

And vice versa: if infrared emitters irradiate an object, this does not mean that its surface absorbs this radiation. It can also reflect, absorb or transmit rays without loss. Almost always, the irradiated object absorbs part of this radiation, reflects part and transmits part.

Not all luminous objects or heated bodies emit infrared waves. For example, fluorescent lamps or the flame of a gas stove do not have such radiation. The operating principle of fluorescent lamps is based on glow (photoluminescence). Its spectrum is closest to the spectrum of daylight, white light. Therefore, there is almost no IR radiation in it. And the highest radiation intensity of a gas stove flame falls on the wavelength blue color. The IR radiation of the listed heated bodies is very weak.

There are also substances that are transparent to visible light, but are not capable of transmitting infrared rays. For example, a layer of water several centimeters thick will not transmit infrared radiation with a wavelength greater than 1 micron. In this case, a person can distinguish objects located at the bottom with the naked eye.