As a result, it was possible to read text that was invisible in normal light. How did he do it? Ultraviolet rays, subject to the general laws of absorption, reflection and refraction electromagnetic waves, at the same time, they are absorbed and reflected by a number of substances differently than visible rays. Some substances have the property of absorbing ultraviolet rays, while others, on the contrary, transmit them unhindered, while remaining opaque to visible light rays. Under the influence of ultraviolet rays, many substances luminesce, that is, they emit visible light. Observing this glow is the most convenient and common way to study ultraviolet rays. When an object under study (for example, a painting or document) is irradiated with ultraviolet rays, details that are invisible under normal lighting become visible. You can take photographs in ultraviolet rays (see Fig. 1). To do this, a layer of luminescent substance is applied to the photosensitive layer of the photographic plate, which converts invisible radiation into visible radiation. Photos obtained this way turn out to be clearer, with more detail.

Visible light is electromagnetic radiation that the human eye perceives. The range of visible light rays ranges from 400 to 700 nm. At a wavelength of more than 700 nm, the infrared spectrum begins, the rays of which are perceived as heat; and at wavelengths less than 400 nm is the ultraviolet (UV) range.

History of the discovery of infrared radiation In 1800, the famous English astronomer and optician W. Herschel, having decomposed sunlight into a spectrum, placed a thermometer behind its red edge, the lower part of the reservoir with mercury was blackened with soot. Having discovered an increase in temperature, he came to the conclusion that the thermometer in this place was heated by some invisible rays. Later they were called infrared.

Definition Infrared radiation is electromagnetic radiation that occupies the spectral region between the red end of visible light and microwave radiation. 50% of the solar radiation energy comes from infrared rays. Artificial sources of this radiation are incandescent lamps with tungsten filament.

Some properties of infrared radiation Sources of radiation: Sun, stars, space, lasers, electric lamps. Infrared rays are emitted by all bodies.

Heat is infrared radiation emitted by moving molecules. When molecules move faster, they emit more infrared radiation and the object is perceived as warmer. The warmer an object is, the faster it emits.

The use of infrared radiation in forensic science The property of infrared rays to be absorbed and reflected by some substances differently than visible light is the basis for their use in forensic practice. For example, photographing in infrared rays allows you to identify erasures in documents and read flooded or smeared texts.

The use of infrared radiation in forensics 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 ones, is expensive for counterfeiters and therefore not economically profitable. Therefore, banknote detectors with a built-in IR emitter are, today, the most reliable protection against counterfeiting.

Application of infrared radiation in medicine For the first time, the biological effect of infrared radiation was discovered in relation to cell cultures, plants, and animals. In most cases, the development of microflora was suppressed. In humans and animals, metabolic processes accelerated, as a result of increased blood flow. It has been proven that infrared radiation has both analgesic, antispasmodic, anti-inflammatory, circulatory, stimulating and distracting effects.

The use of infrared radiation in medicine Infrared radiation also makes it possible to weaken the effect of pesticides, accelerates the recovery process of patients with influenza, and can serve as a measure for the prevention of colds.

In addition, infrared radiation is used in industries such as Food industry Remote control Painting Food sterilization Anti-corrosion agent

History of the discovery of ultraviolet radiation After the discovery of infrared radiation German physicist Johann Wilhelm Ritter began searching for radiation at the opposite end of the spectrum, with a wavelength shorter than violet. In 1801, he discovered that the blackening of silver chloride under the influence of invisible radiation outside the violet region of the spectrum occurs more strongly and faster than under the influence of light. This type of radiation was called ultraviolet.

Definition Ultraviolet radiation (ultraviolet rays, UV radiation) is electromagnetic radiation occupying the spectral range between visible and x-ray radiation. The term comes from Lat. ultra - “above”, “beyond” and “purple”. In colloquial speech the name “ultraviolet” can also be used.

Some properties of ultraviolet radiation Ultraviolet radiation occurs when the states of electrons in the outer shells of an atom or molecules change. Ultraviolet radiation is absorbed by glass, so quartz lenses and prisms are used to study it. Ultraviolet radiation has a shorter wavelength than violet rays and is refracted more strongly than violet rays.

Some properties of ultraviolet radiation Sources of radiation: Sun, stars, nebulae, space, lasers, fluorescent lamps, electric welding, etc. Ultraviolet radiation - affects photocells, luminescent substances, has a bactericidal effect, causes photochemical reactions, is absorbed by ozone, has medicinal properties, invisible.

Application of ultraviolet radiation in medicine Ultraviolet rays reduce the excitability of sensory nerves (painkiller effect). Under the influence of ultraviolet rays, oxidative processes in the body intensify, the absorption of oxygen by tissues and the release of carbon dioxide increases, enzymes are activated, and protein and carbohydrate metabolism improves. The content of calcium and phosphates in the blood increases. Hematopoiesis, regenerative processes, blood supply and tissue trophism improve. Skin blood vessels dilate, blood pressure decreases, and the overall biotone of the body increases.

The use of ultraviolet radiation on the farm Ultraviolet radiation is often used when catching insects with light (often in combination with lamps emitting in the visible part of the spectrum). This is due to the fact that in most insects the visible range is shifted, compared to human vision, to the short-wave part of the spectrum: insects do not see what humans perceive as red, but see soft ultraviolet light.

Ultraviolet radiation can also be used for Sterilization of air and hard surfaces Disinfection drinking water UV spectrometry Mineral analysis Insect catching Artificial tanning

Content:

• Introduction
• Properties
• Application
• Sources
• Impact on humans

• We know that the length of electromagnetic waves can be very different: from values ​​​​of the order of 103 m (radio waves) to 10-8 cm ( X-rays). Light makes up a tiny part of the broad spectrum of electromagnetic waves. However, it was during the study of this small part of the spectrum that other radiations with unusual properties were discovered. Ultraviolet radiation is electromagnetic radiation invisible to the eye, occupying the region between the lower limit of the visible spectrum and the upper limit of x-ray radiation. The wavelength of UV radiation ranges from 100 to 400 nm (1 nm = 10-9 m). According to the classification of the International Commission on Illumination (CIE), the UV radiation spectrum is divided into three ranges: UV-A - long wavelength (315 - 400 nm) UV-B - medium wavelength (280 - 315 nm) UV-C - short wavelength (100 - 280 nm.)

• High chemical activity, invisible, high penetrating ability, kills microorganisms, in small doses has a beneficial effect on the human body (tanning), but in large doses it has a negative biological effect: changes in cell development and metabolism, effects on the eyes.

• IN modern world ultraviolet radiation finds the most wide application V various areas: 1) Medicine. The use of ultraviolet radiation in medicine is due to the fact that it has bactericidal, mutagenic, therapeutic (medicinal), antimitotic and preventive effects, disinfection; laser biomedicine 2) Cosmetology. In cosmetology, ultraviolet irradiation is widely used in solariums to obtain an even, beautiful tan. A deficiency of ultraviolet rays leads to vitamin deficiency, decreased immunity, weak functioning of the nervous system, and the appearance of mental instability. Ultraviolet radiation has a significant effect on phosphorus-calcium metabolism, stimulates the formation of vitamin D and improves all metabolic processes in the body.

• 3) Food industry. Disinfection of water, air, premises, containers and packaging with UV radiation. It should be emphasized that the use of ultraviolet radiation as a physical factor influencing microorganisms can ensure disinfection of the habitat in a very high degree, for example up to 99.9%. 4) Agriculture and livestock farming. 5) Printing. The technology of molding polymer products under the influence of ultraviolet radiation (photochemical molding) is used in many fields of technology. In particular, this technology is widely used in printing and in the production of seals and stamps. Forensics. 6) Show business. Lighting, lighting effects.

• radiated by everyone solids, for which t>1000оС, as well as luminous mercury vapor.
• stars (including the Sun).
• - laser installations;
• - gas-discharge lamps with quartz tubes (quartz lamps), mercury;
• - mercury rectifiers.

• Positive. In sunlight, 40% of the spectrum is visible light, 50% is infrared, and 10% is ultraviolet. It is well known that it is UV rays that initiate the process of formation of vitamin D, which is necessary for the body to absorb calcium and ensure the normal development of the bone skeleton. In addition, ultraviolet radiation actively affects the synthesis of hormones responsible for the daily biological rhythm. Studies have shown that when blood serum was irradiated with UV rays, the content of serotonin, the “hormone of vivacity” involved in the regulation of emotional state. Its deficiency can lead to depression and mood swings. At the same time, the amount of melatonin, which has an inhibitory effect on the endocrine and central nervous system, decreased by 28%. Another aspect of the positive effect of UV rays on the body is their bactericidal function.

• There are a number of effects that occur when the human body is exposed to UV radiation, which can lead to a number of serious structural and functional damages. As is known, these damages can be divided into: - caused by a large dose of radiation received in a short time (for example, sunburn). They occur primarily due to UVB rays, the energy of which is many times greater than the energy of UVA rays. - caused by prolonged exposure to moderate doses. They arise mainly due to UVA rays, which carry less energy, but are able to penetrate deeper into the skin, and their intensity varies little throughout the day and practically does not depend on the time of year.

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The presentation on the topic “Infrared and ultraviolet radiation” can be downloaded absolutely free on our website. Project subject: Physics. Colorful slides and illustrations will help you engage your classmates or audience. To view the content, use the player, or if you want to download the report, click on the corresponding text under the player. The presentation contains 19 slide(s).

Presentation slides

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In 1800, the famous English astronomer and optician W. Herschel, having decomposed sunlight into a spectrum, placed a thermometer behind its red edge, the lower part of the reservoir with mercury was blackened with soot. Having discovered an increase in temperature, he came to the conclusion that the thermometer in this place was heated by some invisible rays. Later they were called infrared.

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Infrared radiation is electromagnetic radiation occupying the spectral region between the red end of visible light (with wavelength λ = 740 nm) and microwave radiation (λ ~ 1-2 mm).

50% of the solar radiation energy comes from infrared rays. Artificial sources of this radiation are incandescent lamps with tungsten filament.

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Sources of radiation: Sun, stars, space, lasers, electric lamps, ... Infrared rays are emitted by all bodies.

Infrared rays have a longer wavelength than red rays and are refracted less than red rays. To study infrared rays, lenses and prisms made of rock salt are used. Infrared rays obey the same laws as visible light, but differ sharply from it in their effect on matter - thermal action.

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A good example of this is an electric heater. When we turn it on, we can feel the coil emitting infrared rays before it turns red. As the spiral gets hotter, the wavelength of the radiation continues to decrease, and eventually we see the spiral turn red as some of the radiation moves closer to the visible range. This is called the incandescent point. As the object continues to heat up, it emits visible radiation, and eventually ultraviolet radiation. The same is true with stars like the sun, which provide us with a full spectrum of light, including infrared rays.

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Application:

Medicine Remote control Painting Food sterilization Anti-corrosion agent Food industry

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Their use in forensic practice is based on the property of infrared rays to be absorbed and reflected by some substances differently than visible light. For example, photographing in infrared rays makes it possible to identify erasures in documents and read flooded or smeared texts (see Fig. 2). The presence of infrared radiation can be detected using luminescence. Some crystal phosphors (solid luminescent substances) are known that produce flashes of light when exposed to infrared radiation. True, for this, the atoms of the substance must be previously excited. Sometimes infrared rays have, on the contrary, a dampening effect on excited crystal phosphorus. In both cases, the result of invisible radiation becomes visible.

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Availability in earth's atmosphere water vapor prevents the rapid cooling of the Earth. The earth emits infrared (thermal) radiation into the surrounding space. However, water vapor, which transmits visible light quite well, absorbs infrared radiation and thereby heats the surrounding air. If this had not happened, then average temperature The Earth's surface would be significantly below 0 °C, while now it is 15 °C.

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After the discovery of infrared radiation, the German physicist Johann Wilhelm Ritter began searching for radiation at the opposite end of the spectrum, with a wavelength shorter than violet. In 1801, he discovered that the blackening of silver chloride under the influence of invisible radiation outside the violet region of the spectrum occurs more strongly and faster than under the influence of light. This type of radiation was called ultraviolet. In the same year, independently of Ritter, ultraviolet radiation was discovered by the English scientist W. Wollaston.

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Ultraviolet radiation occurs when the states of electrons in the outer shells of an atom or molecules change.

Ultraviolet radiation has a shorter wavelength than violet rays and is refracted more strongly than violet rays. Ultraviolet radiation is absorbed by glass, so quartz lenses and prisms are used to study it.

Ultraviolet radiation obeys the same laws as visible light, but differs sharply from it in its effect on the substance; chemical and biological activity is observed

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Radiation sources: Sun, stars, nebulae, space, lasers, fluorescent lamps, electric welding, etc.

Ultraviolet radiation - affects photocells, luminescent substances, has a bactericidal effect, causes photochemical reactions, is absorbed by ozone, has healing properties, is invisible.

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When exposed to living organisms, ultraviolet radiation is absorbed by the upper layers of plant tissue or human and animal skin. It has the smallest depth of penetration into tissue - only up to 1 mm. Therefore, its direct influence is limited to the superficial layers of the irradiated areas of the skin and mucous membranes. Sensitivity to ultraviolet rays is increased in children, especially in early age. Small doses have a beneficial effect on humans and animals - they promote the formation of group D vitamins and improve the immunobiological properties of the body.

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The expert photographed the document in ultraviolet rays. As a result, it was possible to read text that was invisible in normal light. How did he do it? Ultraviolet rays, obeying the general laws of absorption, reflection and refraction of electromagnetic waves, are at the same time absorbed and reflected by a number of substances differently than visible rays. Some substances have the property of absorbing ultraviolet rays, while others, on the contrary, transmit them unhindered, while remaining opaque to visible light rays. Under the influence of ultraviolet rays, many substances luminesce, that is, they emit visible light. Observing this glow is the most convenient and common way to study ultraviolet rays. When an object under study (for example, a painting or document) is irradiated with ultraviolet rays, details that are invisible under normal lighting become visible. You can take photographs in ultraviolet rays (see Fig. 1). To do this, a layer of luminescent substance is applied to the photosensitive layer of the photographic plate, which converts invisible radiation into visible radiation. Photos obtained this way turn out to be clearer, with more detail.

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