Length and frequency of infrared radiation. Little-Known Facts About IR Light

What is infrared radiation? The definition states that infrared rays are electromagnetic radiation that obeys optical laws and is of the nature of visible light. Infrared rays have a spectral range between red visible light and short-wave radio emission. For the infrared region of the spectrum there is a division into short-wave, medium-wave and long-wave. The heating effect of such rays is high. The accepted abbreviation for infrared radiation is IR.

IR radiation

Manufacturers report different information about heating devices designed according to the principle of radiation in question. Some may indicate that the device is infrared, while others may indicate that it is long-wave or dark. All this in practice relates to infrared radiation; long-wave heaters have the lowest temperature of the radiating surface, and waves are emitted in greater mass in the long-wave zone of the spectrum. They also received the name dark, since at temperature they do not give off light and do not shine, as in other cases. Medium wave heaters have a higher surface temperature and are called gray heaters. The light type is a short-wave device.

The optical characteristics of a substance in the infrared regions of the spectrum differ from the optical properties in ordinary everyday life. Heating devices that people use every day give off infrared rays, but you don't see them. The whole difference is in the wavelength, it varies. An ordinary radiator emits rays, which is how the room is heated. Infrared radiation waves are present in human life naturally; the sun emits them.

Infrared radiation belongs to the category of electromagnetic, that is, it cannot be seen with the eyes. Wavelengths range from 1 millimeter to 0.7 micrometers. The biggest source of infrared rays is the sun.

IR rays for heating

The presence of heating based on this technology allows you to get rid of the disadvantages of the convection system, which is associated with the circulation of air flow in the premises. Convection raises and carries dust, debris, and creates a draft. If you install an electric infrared heater, it will work on the principle of solar rays, the effect will be similar to solar heat in cool weather.

Infrared wave is a form of energy, it is a natural mechanism borrowed from nature. These rays are capable of heating not only objects, but also the air space itself. The waves penetrate the air layers and heat objects and living tissues. Localization of the source of the radiation in question is not so important; if the device is on the ceiling, the heating rays will reach the floor perfectly. It is important that infrared radiation allows you to leave the air moist, it does not dry it out, as other types do heating devices. The performance of devices based on infrared radiation is extremely high.

Infrared radiation does not require large energy costs, so there are savings for household use of this development. IR rays are suitable for working in large spaces; the main thing is to choose the right ray length and set up the devices correctly.

Harm and benefits of infrared radiation

Long infrared rays hitting the skin cause a reaction in nerve receptors. This ensures the presence of heat. Therefore, in many sources, infrared radiation is called thermal radiation. Most of the emitted energy is absorbed by the moisture contained in top layer human skin. Therefore, the skin temperature rises, and due to this, the entire body is heated.

There is an opinion that infrared radiation is harmful. This is wrong.

Research shows that long-wave radiation is safe for the body, moreover, it has benefits.

They strengthen the immune system, stimulate regeneration and improve the condition of internal organs. These rays with a length of 9.6 microns are used in medical practice for therapeutic purposes.

Shortwave infrared radiation works differently. It penetrates deep into the tissue and warms the internal organs, bypassing the skin. If you irradiate the skin with such rays, the capillary network expands, the skin turns red, and signs of a burn may appear. Such rays are dangerous for the eyes, they lead to the formation of cataracts, disrupt the water-salt balance, and provoke seizures.

A person gets heatstroke due to short-wave radiation. If you increase the temperature of the brain by even a degree, then signs of shock or poisoning already appear:

  • nausea;
  • rapid pulse;
  • darkening in the eyes.

If overheating occurs by two degrees or more, then meningitis develops, which is life-threatening.

The intensity of infrared radiation depends on several factors. The distance to the location of heat sources and the indicator are important temperature regime. Long-wave infrared radiation is important in life, and it is impossible to do without it. Harm can only occur when the wavelength is incorrect and the time it affects a person is long.

How to protect a person from the harm of infrared radiation?

Not all infrared waves are harmful. Shortwave infrared energy should be avoided. Where is it found in Everyday life? Body temperatures above 100 degrees should be avoided. This category includes steelmaking equipment and electric arc furnaces. In production, employees wear specially designed uniforms that have a protective shield.

The most useful infrared heating device was the Russian stove; the heat from it was therapeutic and beneficial. However, no one uses such devices now. Infrared heaters have become firmly established, and infrared waves are widely used in industry.

If the spiral that gives off heat in an infrared device is protected by a heat insulator, then the radiation will be soft and long-wave, and this is safe. If the device has an open a heating element, then the infrared radiation will be hard, short-wave, and this is dangerous to health.

In order to understand the design of the device, you need to study the technical data sheet. There will be information about the infrared rays used in a particular case. Pay attention to what the wavelength is.

Infrared radiation is not always clearly harmful; only open sources, short rays and prolonged exposure to them emit danger.

You should protect your eyes from the source of the waves, and if discomfort occurs, move away from the influence of infrared rays. If unusual dryness appears on the skin, it means that the rays are drying out the lipid layer, and this is very good.

Infrared radiation in useful ranges is used as treatment; physiotherapy methods are based on working with rays and electrodes. However, all effects are carried out under the supervision of specialists; you should not treat yourself with infrared devices. The duration of action must be strictly determined by medical indications, based on the goals and objectives of treatment.

It is believed that infrared radiation is unfavorable for systematic exposure to small children, so it is advisable to carefully select heating devices for the bedroom and children's rooms. You will need the help of specialists to set up a safe and effective infrared network in your apartment or house.

Don't give up modern technologies due to prejudice due to ignorance.

Gamma radiation Ionizing Relict Magnetic drift Two-photon Spontaneous Forced

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

The optical properties of substances in infrared radiation differ significantly from their properties in visible radiation. For example, a layer of water of several centimeters is opaque to infrared radiation with λ = 1 μm. Infrared radiation makes up most of the radiation from incandescent lamps, gas-discharge lamps, and about 50% of the radiation from the Sun; Some lasers emit infrared radiation. To register it, they use thermal and photoelectric receivers, as well as special photographic materials.

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

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

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

Infrared radiation is also called “thermal” radiation, since infrared 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. The radiation 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.

Discovery history and general characteristics

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

Previously, laboratory sources of infrared radiation were exclusively hot bodies or electrical discharges in gases. Nowadays, modern sources of infrared radiation with adjustable or fixed frequency have been created based on solid-state and molecular gas lasers. To record radiation in the near-infrared region (up to ~1.3 μm), special photographic plates are used. Photoelectric detectors and photoresistors have a wider sensitivity range (up to approximately 25 microns). Radiation in the far infrared region is recorded by bolometers - detectors that are sensitive to heating by infrared radiation.

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

Since infrared spectra are associated with rotational and vibrational movements in the molecule, as well as with electronic transitions in atoms and molecules, IR spectroscopy allows one to obtain important information about the structure of atoms and molecules, as well as the band structure of crystals.

Application

Medicine

Infrared rays are used in physiotherapy.

Remote control

Infrared diodes and photodiodes are widely used in remote controls, 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 remote control Easily captured using a digital camera.

When painting

Infrared emitters are used in industry for drying paint surfaces. The infrared drying method has significant advantages over the traditional convection method. First of all, this is, of course, an economic effect. The speed and energy consumed during infrared drying is less than the same indicators with traditional methods.

Food Sterilization

Infrared radiation is used to sterilize food products for disinfection.

Anti-corrosion agent

Infrared rays are used to prevent corrosion of surfaces coated with varnish.

Food industry

The peculiarity of the use of IR radiation in Food Industry is the possibility of penetration of an electromagnetic wave into capillary-porous products such as grain, cereals, flour, etc. to a depth of 7 mm. This value depends on the nature of the surface, structure, material properties and frequency characteristics of the radiation. Electromagnetic wave a certain frequency range has not only a thermal, but also a biological effect on the product, helping to accelerate biochemical transformations in biological polymers (starch, protein, lipids). Conveyor drying conveyors can be successfully used when storing grain in granaries and in the flour-grinding industry.

In addition, infrared radiation is widely used to heat indoor and outdoor spaces. Infrared heaters are used to organize additional or main heating in rooms (houses, apartments, offices, etc.), as well as for local heating of outdoor space (outdoor cafes, gazebos, verandas).

The disadvantage is the significantly greater unevenness of heating, which in some cases technological processes completely unacceptable.

Checking money for authenticity

An infrared emitter is used in devices for checking money. Applied to the banknote as one of the security elements, special metameric inks can be seen exclusively in the infrared range. Infrared currency detectors are the most error-free devices for checking the authenticity of money. Applying infrared marks to a banknote, unlike ultraviolet marks, is expensive for counterfeiters and therefore not economically profitable. Therefore, banknote detectors with a built-in IR emitter, today, are the most reliable protection from fakes.

Health Hazard

Strong infrared radiation in hot areas may cause eye hazard. It is most dangerous when the radiation is not accompanied by visible light. In such places it is necessary to wear special eye protection.

see also

Other heat transfer methods

Methods for registering (recording) IR spectra.

Notes

Links

Occupying the spectral region between the red end of visible light (with a full length l, ca. 0.76 µm) and short-wave radio emission (l ~ 1-2 mm). Top, border of I. and. is determined by the sensitivity of the human eye to visible radiation, and the lower one is conditional, since the IR range overlaps with the radio wavelength range. The IR region of the spectrum is usually divided into near (0.76-2.5 µm), mid (2.5-50 µm) and far (50-2000 µm). I. and. obeys all the laws of optics and belongs to optical science. radiation. I. and. not visible to the eye, but creates a feeling of warmth and is therefore often called. thermal. Spectrum I. and. may consist of dept. lines, stripes or be continuous depending on the source emitting it. Ruled

Rice. 1. Infrared spectrum of mercury radiation. 1-12 - spectral lines, the wavelengths of which in microns are equal to: 1 - 1.014; 2 - 1.129; 3 - 1.357; 4 - 1.367; 5 - 1.395; 6 - 1.530; 7 - 1.692; 8 - 1.707 and 1.711; 9 - 1.814; 10 - 1.970; 11 - 2.249; 12 - 2.326.

IR spectra emit excited atoms or ions during transitions between closely spaced electronic levels energy (Fig. 1; see Atomic spectra).Striped IR spectra are observed in the emission spectra of excited molecules that arise during transitions between vibrations. and rotate. energy levels, - oscillation. and rotate. spectra (see Molecular spectra). Fluctuation. and oscillatory-rotate. The spectra are located in ch. arr. in the middle, and purely rotational - in the far IR region. Continuous infrared spectrum is emitted by heated solids and liquids. Abs. and relates, the share of I. and. heated solid depends on its temperature. At temp-pax below 500 K, the radiation is almost entirely located in the IR region (the body appears dark). However, the total radiation energy at such temps is small. As the temperature increases, the proportion of radiation in the visible region increases, the body becomes dark red, then red, yellow, and finally, at temperatures above 5000 K, white; At the same time, along with the total radiation energy, the energy of the radiation source also increases. A strict dependence of the radiation energy of heated bodies on temperature exists only for absolutely black body. all length ranges

Rice. 2. Blackbody radiation curves L and tungsten IN at a temperature of 2450 °K. The shaded part is tungsten radiation in the IR region; interval 0.4-0.74 µm - visible region.

waves of real bodies are less than the radiation of an absolutely black body of the same temperature, and can be selective. For example, the radiation of incandescent tungsten in the IR region differs from the radiation of a black body more than in the visible region of the spectrum (Fig. 2). The radiation of the Sun is close to the radiation of an absolutely black body with a temperature of about 6000 8K, and about 50% of the radiation energy is located in the IR region. The radiation energy distribution of the human body in the IR region is close to the energy distribution of black radiation with a maximum at l~9.5 μm.

Sources I. and. The most common sources of radiation are incandescent lamps with a tungsten filament with a power of up to 1 kW, 70-80% of the emitted energy of which is in the infrared range (they are used, for example, for drying and heating), as well as coal electricity. arc, gas discharge lamps, electric spirals made of nichrome wire. For IR photography and in certain IR devices (for example, night vision devices) for isolating I. and. IR filters are used. In scientific research (eg in infrared spectroscopy) apply different specialist. sources I. and. depending on the region of the spectrum. Thus, in the near-IR region (l = 0.76-2.5 μm) the source of I. and. a tungsten strip lamp is used, in the mid-IR region (2.5-25 microns) - a Nernst pin and a globar, in the region l ~ 20 -100 microns - a platinum strip coated with a thin layer of oxides of certain rare earth metals; in the far IR region (100-1600 microns) - mercury quartz lamp high pressure. Sources of I. and. There are several IR lasers: laser on neodymium glass (l = 1.06 µm), helium-neon laser (l = 1.15 µm and 3.39 µm), CO laser (l ~ 5.08 -6.66 µm), CO 2 laser (l ~ 9.12-11.28 µm), water vapor laser (l ~ 118.6 µm), HCN laser (l ~ 773 µm), chemical. laser on a mixture of H 2 and C1 2 (l ~ 3.7-3.8 μm), on GaAs (l ~ 0.83-0.92 μm), InSb (l ~ 4.8-5.3 μm), (Pb, Sn) Te (l~6.5-32 μm), etc. Many IR lasers can operate in the tunable radiation frequency mode.

Methods for detecting and measuring I. and. are based on the conversion of energy and. In other types of energy, registration methods for which are well developed. In thermal receivers, the absorbed energy is causes an increase in the temperature of the thermosensitive. element, which is registered in one way or another. Heat receivers can operate in almost the entire field of thermal imaging. In photovoltaic receivers absorbed I. and. leads to the appearance or change of electrical current or . Such receivers, unlike thermal ones, are selective, that is, they are sensitive only to a certain extent. IR spectral region (see Optical radiation receivers). Mn. photovoltaic receivers I. and. especially for the mid- and far-IR regions of the spectrum, they work only in a cooled state. As receivers of I. and. devices based on amplification or luminescence quenching, under the influence of I. and., as well as the so-called. anti-Stokes phosphors (see Anti-Stokes luminescence), directly transforming I. and. to visible (luminophore with Yb and Er ions converts radiation l=1.06 μm into visible radiation with l=0.7 μm). Specialist. photographic films and plates - infraplates - are also sensitive to radiation. (up to l=1.3 µm). There are also special devices that allow by registering your own. thermal I. and. obtain the temperature distribution over the surface of an object, i.e. its thermal (or temperature) image. This is the so-called The thermal image can be converted into a visible image, in which the brightness of the visible image in the dep. points is proportional to the temperature of the corresponding points of the object. The image obtained in these devices is not an IR image in the usual sense, since it only gives a picture of the distribution of darkness on the surface of the object. Visualization devices I. and. are divided into non-scanning and scanning. In the first I. and. recorded directly on photographic film or a fluorescent screen, as well as on the screen using electron-optical converters(EOP) or evaporographs. Scanning devices include thermal imagers or thermographs with optical-mechanical. scanning an object. The area of ​​sensitivity of the image intensifier is determined by sensitivity to And. and. and does not exceed l=1.3 µm. Evaporographs and thermal imagers can be used in the mid-IR region, and therefore they allow you to obtain thermal images of low-temperature bodies. There are also parametric methods. transformations I. and. into visible radiation when mixing I. and. With laser radiation in optically nonlinear crystals (see Parametric light generator).

Optical properties of substances in the IR region of the spectrum(transparency, reflection coefficient, refractive index), as a rule, differ significantly from optical ones. properties in the visible and UV regions of the spectrum. Mn. substances that are transparent in the visible region turn out to be opaque in certain areas of vision, and vice versa. For example, layer


several layers of water thick. cm is opaque to I. and. with l>1 µm (therefore water is often used as a heat-protective filter), germanium and silicon plates, opaque in the visible region, are transparent to radiation. (germanium for l>1.8 µm, silicon for l>1.0 µm). Black paper is transparent in the far infrared region. Substances transparent to I. and. and opaque in the visible region, are used as light filters for highlighting and.

Rice. 3. Reflection infrared radiation from alkali halide crystals.

Absorption of I. and. for most substances in thin layers it is selective in the form of relatively narrow regions - absorption bands. Certain substances, ch. arr. single crystals, even with a thickness of up to several. cm are transparent in fairly large certain ranges of the IR spectrum. In table The long-wave limit l g of transmission of certain materials used in the infrared region of the spectrum for the manufacture of prisms, lenses, windows, etc. is given. parts (materials marked with an asterisk are hygroscopic). Polyethylene, paraffin, Teflon, diamond are transparent for l>100 microns (transmittance more than 50% at a thickness of 2 mm). Reflect. ability for I. and. for most metals it is significantly greater than for the visible region, and increases with increasing l I. and. (cm. Metal optics).For example, coefficient. reflection of Al, Au, Ag, Cu in the region l=10 µm reaches 98%. Liquid and solid non-metallic. substances have selective reflection in the IR region, and the position of the reflection maxima depends on the chemical. composition of the substance. Some


Rice. 4. Atmospheric transmission curve in the region l=0.6-14 µm. "Windows" of transparency in the region [email protected] microns; 3.2-4.2 microns; 4.5-5.2 microns; 8.0-13.5 microns. Absorption bands with maxima at [email protected]; 1.13; 1.40; 1.87; 2.74; 6.3 microns belong to water vapor; at l=2.7, 4.26 and 15.0 µm - carbon dioxide and at [email protected] µm - ozone.

crystal coefficient reflection at the maximum selective reflection (Fig. 3) reaches large values(up to 80%), and therefore plates made from such crystals can serve as reflectors. filters to highlight certain regions I. and. (the so-called residual ray method). Transparency of the earth's atmosphere for I. and. (as well as for visible and UV radiation) plays a large role in the process of thermal radiation. exchange between the radiation of the Sun falling on the Earth and I. and. Earth into world space (the Earth's return radiation is located mainly in the spectral region with a maximum of about 10 μm), and is also significant in practical applications. use of I. and. (for communications, in infrared photography, for the use of radiation in military affairs, etc.). Passing through the earth's atmosphere, I. and. is attenuated as a result of scattering (see Light Scattering) and absorption. Nitrogen and oxygen in the air do not absorb radiation, but weaken it only as a result of scattering, which is much less than for the radiation of visible light (since the scattering coefficient is ~l - 4). Water vapor, CO 2 , ozone, and other impurities present in the atmosphere selectively absorb iodine. I. and. absorb especially strongly. water vapor, absorption bands of which are located almost in the entire IR region of the spectrum (Fig. 4). Thanks to the strong absorption of And. and. the earth's atmosphere just not most of reverse I. and. The Earth extends beyond the atmosphere, i.e. the atmosphere serves as a heat-insulating shell that prevents the Earth from cooling. The presence in the atmosphere of particles of smoke, dust, and small drops of water (haze, fog) leads to additional, weakening of I. and. as a result of scattering on these particles, and the amount of scattering depends on the ratio of the particle sizes and the wavelength of the radiation.

Applications of IR radiation. I. N. is widely used in scientific research. research, when deciding large number practical tasks, in military affairs, etc. The study of emission and absorption spectra of substances in the IR region is a complement to research in the visible and UV regions and is used in studying the structure of the electronic shell of atoms, determining the structure of molecules, as well as for qualities and quantities. spectral analysis. IR lasers (especially those with tunable frequency; see Fig. Laser spectroscopy). Thanks to the peculiarities of interaction between I. and. with matter, IR photography has a number of advantages over visible photography. So, as a result of less weakening of I. and. Due to scattering when passing through haze and light fog and using infrared films and IR filters, it is possible to obtain IR photographs of objects located at a distance of hundreds of kilometers. Photographs of the same object obtained in I. and. and in visible light, due to the difference in coefficient. The reflections and transmission of an object can vary significantly, and in IR photography you can see details that are invisible in regular photography and directly with the eye, which is used when photographing earth's surface from Earth satellites, in botany, medicine, criminology, aerial photography, etc. On IR photographs, dept. areas of the sky can often be seen larger number stars, nebulae and other objects than in ordinary photographs. Photographing in I. and. can also be carried out in complete darkness when irradiating objects. In industry I. and. used for drying (including local) decomposition. materials and products. Based on electron-optical converters that are sensitive to radiation, various types of night vision devices (binoculars, sights, etc.) have been created, which make it possible to irradiate observed objects with radiation. from special sources with light filters to observe or aim in complete darkness. Evaporographs and thermal imagers are used in industry to detect overheated areas of machines or electronic devices, to obtain temperature maps of the area, etc. The creation is highly sensitive. receivers I. and. (eg. bolometers or cooled photoresistors) made it possible to build heat direction finders for detecting and direction finding objects whose temperature is higher than the temperature of the surrounding background (heated ship pipes, aircraft engines, etc.), on their own. thermal I. and. Homing systems for targeting shells and missiles have also been created. IR locators and rangefinders allow you to detect any objects in the dark and measure distances to them. IR lasers are also used for ground and space applications. communications. Lit.: Lecomte J., Infrared radiation, trans. from French, M., 1958; Soloviev S. M., Infrared photography, M., I960; Optical materials for infrared technology. [Reference book], M., 1965; Kozelkin V.V., Usoltsev I.F., Fundamentals of infrared technology, 3rd ed., M., 1985; Markov M.N., Infrared radiation receivers, M., 1968; Receivers of infrared radiation, trans. from French, M., 1969; Hudson R., Infrared systems, trans. from English, M., 1972; Lloyd J., Thermal Imaging Systems, trans. from English, M., 1978; Levitin I. B., Application of infrared technology in national economy. L., 1981; Gibson X., Photography in Infrared Rays, trans. from English, M., 1982. IN. I. Malyshev.

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

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

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

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

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

Sources

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

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

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

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

Receivers

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

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

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

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

Sky Reviews

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

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

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

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

Terrestrial Application

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

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

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

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

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

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

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

Discovery of infrared radiation
Types of heat exchange
Physical properties
Range of IR waves favorable for humans

The English researcher Herschel W. in 1800, in the process of studying sunlight, established that in Sun rays when they are decomposed into separate spectra using a prism beyond the red visible spectrum, the thermometer readings increase. A thermometer placed in this area showed high temperature than a calibration thermometer. Later it was established that the properties of these rays are amenable to the laws of optics, and it turns out that they have the same nature as 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 upon contact or through a separator),
convection(heat transfer by coolant, liquid or gas from a heat source to colder objects)
thermal radiation(a flow 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 have the same nature as light radiation. The IR beam is located between the red light perceived by humans (0.7 µm) and short-wave radio emission (1 - 2 mm). In addition, the IR region of the spectrum is divided into short-wave (0.7 - 2 µm), medium-wave (from 2 to 5.1 µm), long wave(5.1 - 200 µm). Infrared rays are emitted by all substances liquid and solid, while The emitted wavelength depends on the temperature of the substance. At higher temperatures, the wavelength emitted by the substance is shorter, but the radiation intensity is greater.

In the range of long-wave radiation (from 9 to 11 microns) there is the most favorable thermal radiation for humans. Long-wave emitters have a lower radiation surface temperature and are characterized as dark - at low surface temperatures they do not glow (up to 300°C). Medium wave emitters with more high temperature surfaces, characterized by gray, radiate with maximum body temperature 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, IR radiation having a wavelength of more than 1 micron, absorbed by water in a layer of 1-2 cm, so water is in some cases used as a heat-protective 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 humans, in addition, their properties significantly improve with increasing radiation wavelength. Namely, The reflection index of Al, Au, Ag at a wavelength of about 10 microns approaches 98%. Considering these properties of materials, they are used in the production 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 you to focus IR radiation in the desired 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, nitrogen and oxygen molecules themselves do not absorb infrared rays, but only slightly scatter, reducing the intensity. Water vapor, ozone, carbon dioxide, as well as 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 of small particles in the air - 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.