Generalizing lesson "Scale of electromagnetic radiation". Electromagnetic radiation - human impact, protection

The scale of electromagnetic radiation conditionally includes seven ranges:

1. Low frequency oscillations

2. Radio waves

3. Infrared radiation

4. Visible radiation

5. Ultraviolet radiation

6. X-rays

7. Gamma rays

There is no fundamental difference between the individual radiations. All of them are electromagnetic waves generated by charged particles. Electromagnetic waves are detected, ultimately, by their action on charged particles. In a vacuum, radiation of any wavelength travels at a speed of 300,000 km/s. The boundaries between individual areas of the radiation scale are very arbitrary.

Radiations of different wavelengths differ from each other in the method of their production (radiation from an antenna, thermal radiation, radiation during deceleration of fast electrons, etc.) and methods of registration.

All of the listed types of electromagnetic radiation are also generated by space objects and are successfully studied using rockets, artificial satellites Earth and spaceships. First of all, this applies to X-ray and g-radiation, which is strongly absorbed by the atmosphere.

As the wavelength decreases, quantitative differences in wavelengths lead to significant qualitative differences.

Radiations of different wavelengths differ greatly from each other in terms of their absorption by matter. Short-wave radiation (X-rays and especially g-rays) are weakly absorbed. Substances that are opaque to optical wavelengths are transparent to these radiations. Reflection coefficient electromagnetic waves also depends on the wavelength. But the main difference between longwave and shortwave radiation is that shortwave radiation reveals the properties of particles.

Infrared radiation

Infrared radiation - electromagnetic radiation occupying the spectral region between the red end of visible light (with a wavelength of λ = 0.74 μm) and microwave radiation(λ ~ 1-2 mm). Is not visible radiation with a pronounced thermal effect.

Infrared radiation was discovered in 1800 by the English scientist W. Herschel.

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

shortwave region: λ = 0.74-2.5 µm;

medium wave region: λ = 2.5-50 µm;

longwave region: λ = 50-2000 µm;

Application

IR (infrared) diodes and photodiodes are widely used in remote controls, automation systems, security systems etc. They do not distract a person's attention due to their invisibility. Infrared emitters are used in industry for drying paint surfaces.

positive side effect so is sterilization food products, increasing the resistance to corrosion of the surfaces covered with paints. The disadvantage is the significantly greater non-uniformity of heating, which in a number technological processes completely unacceptable.

An electromagnetic wave of a certain frequency range has not only a thermal, but also a biological effect on the product, and contributes to the acceleration of biochemical transformations in biological polymers.

In addition, infrared radiation is widely used for heating rooms and outdoor spaces.

In night vision devices: binoculars, glasses, sights for small arms, night photo and video cameras. Here, the infrared image of the object, invisible to the eye, is converted into a visible one.

Thermal imagers are used in construction when assessing thermal insulation properties structures. With their help, you can determine the areas of greatest heat loss in a house under construction and draw a conclusion about the quality of the applied building materials and heaters.

Strong infrared radiation in high heat areas can be hazardous to the eyes. It is most dangerous when the radiation is not accompanied by visible light. In such places it is necessary to wear special protective goggles for the eyes.

Ultraviolet radiation

Ultraviolet radiation (ultraviolet, UV, UV) - electromagnetic radiation, occupying the range between the violet end of visible radiation and X-ray radiation (380 - 10 nm, 7.9 × 1014 - 3 × 1016 Hz). The range is conditionally divided into near (380-200 nm) and far, or vacuum (200-10 nm) ultraviolet, the latter is so named because it is intensively absorbed by the atmosphere and is studied only by vacuum devices. This invisible radiation has a high biological and chemical activity.

The concept of ultraviolet rays is first encountered by a 13th century Indian philosopher. The atmosphere of the area he described contained violet rays that cannot be seen with the normal eye.

In 1801, physicist Johann Wilhelm Ritter discovered that silver chloride, which decomposes under the action of light, decomposes faster under the action of invisible radiation outside the violet region of the spectrum.

UV Sources
natural springs

The main source of ultraviolet radiation on Earth is the Sun.

artificial sources

UV DU type "Artificial solarium", which use UV LL, causing a fairly rapid formation of a tan.

UV lamps used for sterilization (disinfection) of water, air and various surfaces in all spheres of human life.

Germicidal UV radiation at these wavelengths causes dimerization of thymine in DNA molecules. The accumulation of such changes in the DNA of microorganisms leads to a slowdown in their reproduction and extinction.

Ultraviolet treatment of water, air and surfaces does not have a prolonged effect.

Biological impact

Destroys the retina of the eye, causes skin burns and skin cancer.

Beneficial features UV radiation

Getting on the skin causes the formation of a protective pigment - sunburn.

Promotes the formation of vitamins of group D

Causes the death of pathogenic bacteria

Application of UV radiation

Use of invisible UV inks for protection bank cards and banknotes from forgery. Images, design elements that are invisible in ordinary light, or make the entire map glow in UV rays are applied to the map.

Many already know that the length of electromagnetic waves can be completely different. Wavelengths can range from 103 meters (for radio waves) to ten centimeters for X-rays.

Light waves are a very small part of the widest spectrum of electromagnetic radiation (waves).

It was during the study of this phenomenon that discoveries were made that open the eyes of scientists to other types of radiation that have rather unusual and previously unknown properties to science.

electromagnetic radiation

There is no cardinal difference between different types of electromagnetic radiation. All of them represent electromagnetic waves, which are formed due to charged particles, the speed of which is greater than that of particles in the normal state.

Electromagnetic waves can be detected by following their action on other charged particles. In absolute vacuum (an environment with a complete absence of oxygen), the speed of movement of electromagnetic waves is equal to the speed of light - 300,000 kilometers per second.

The boundaries set on the measurement scale of electromagnetic waves are rather unstable, or rather conditional.

Electromagnetic radiation scale

Electromagnetic radiation, which has a wide variety of lengths, is distinguished from each other by the way in which they are obtained (thermal radiation, antenna radiation, as well as radiation obtained as a result of slowing down the speed of rotation of the so-called "fast" electrons).

Also, electromagnetic waves - radiation, differ in the methods of their registration, one of which is the scale of electromagnetic radiation.

Objects and processes that exist in space, such as stars, black holes that appear as a result of the explosion of stars, also generate the listed types of electromagnetic radiation. The study of these phenomena is carried out with the help of artificially created satellites, rockets launched by scientists and spacecraft.

In most cases, research work aimed at studying gamma and x-ray radiation. The study of this type of radiation is almost impossible to fully explore on the surface of the earth, since most of the radiation emitted by the sun is retained by the atmosphere of our planet.

Reducing the length of electromagnetic waves inevitably leads to quite significant qualitative differences. Electromagnetic radiation, having different lengths, have a great difference between themselves, according to the ability of substances to absorb such radiation.

Radiation with low wavelengths (gamma rays and X-rays) is weakly absorbed by substances. For gamma and X-rays, substances that are opaque to optical radiation become transparent.

Zemtsova Ekaterina.

Research.

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"Scale of electromagnetic radiation." The work was done by a student of the 11th grade: Ekaterina Zemtsova Supervisor: Firsova Natalya Evgenievna Volgograd 2016

Contents Introduction Electromagnetic Radiation Electromagnetic Radiation Scale Radio Waves Influence of Radio Waves on the Human Body How can one protect oneself from radio waves? Infrared radiation The effect of infrared radiation on the body Ultraviolet radiation X-ray radiation The effect of x-rays on a person The effect of ultraviolet radiation Gamma radiation The effect of radiation on a living organism Conclusions

Introduction Electromagnetic waves are inevitable companions of domestic comfort. They permeate the space around us and our bodies: sources of EM radiation warm and light houses, serve for cooking, provide instant communication with any corner of the world.

Relevance The influence of electromagnetic waves on the human body today is the subject of frequent disputes. However, it is not the electromagnetic waves themselves that are dangerous, without which no device could really work, but their information component, which cannot be detected by conventional oscilloscopes. * An oscilloscope is a device designed to study the amplitude parameters of an electrical signal *

Objectives: To consider each type of electromagnetic radiation in detail To identify what effect it has on human health

Electromagnetic radiation is a perturbation propagating in space (change of state) electromagnetic field. Electromagnetic radiation is divided into: radio waves (starting with extra long), infrared radiation, ultraviolet radiation, X-ray radiation gamma radiation (hard)

The scale of electromagnetic radiation is the totality of all frequency ranges of electromagnetic radiation. The following quantities are used as a spectral characteristic of electromagnetic radiation: Wavelength Oscillation frequency Energy of a photon (quantum of an electromagnetic field)

Radio waves are electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 3 kHz to 300 GHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves, radio waves travel at the speed of light. Natural sources of radio waves are lightning and astronomical objects. Artificially generated radio waves are used for fixed and mobile radio communications, radio broadcasting, radar and other navigation systems, communications satellites, computer networks, and countless other applications.

Radio waves are divided into frequency ranges: long waves, medium waves, short waves, and ultrashort waves. The waves in this range are called long because their low frequency corresponds to a long wavelength. They can spread for thousands of kilometers, as they are able to bend around the earth's surface. Therefore, many international radio stations broadcast on long waves. Long waves.

They do not propagate over very long distances, since they can only be reflected from the ionosphere (one of the layers of the Earth's atmosphere). Medium wave transmissions are better received at night, when the reflectivity of the ionospheric layer increases. medium waves

Short waves are repeatedly reflected from the surface of the Earth and from the ionosphere, due to which they propagate over very long distances. Transmissions from a shortwave radio station can be received on the other side of the globe. - can only be reflected from the surface of the Earth and therefore are suitable for broadcasting only at very short distances. On the waves of the VHF band, stereo sound is often transmitted, since interference is weaker on them. Ultrashort waves (VHF)

Influence of radio waves on the human body What parameters differ in the impact of radio waves on the body? Thermal action can be explained with an example human body: encountering an obstacle on the way - the human body, the waves penetrate into it. In humans, they are absorbed top layer skin. At the same time, it forms thermal energy which is excreted by the circulatory system. 2. Non-thermal action of radio waves. A typical example is the waves coming from a mobile phone antenna. Here you can pay attention to the experiments conducted by scientists with rodents. They were able to prove the impact on them of non-thermal radio waves. However, they failed to prove their harm to the human body. What is successfully used by both supporters and opponents of mobile communications, manipulating people's minds.

The skin of a person, more precisely, its outer layers, absorbs (absorbs) radio waves, as a result of which heat is released, which can be absolutely accurately recorded experimentally. The maximum allowable temperature increase for the human body is 4 degrees. It follows that for serious consequences, a person must be exposed to fairly powerful radio waves for a long time, which is unlikely in everyday life. living conditions. It is widely known that electromagnetic radiation interferes with high-quality TV signal reception. Radio waves are deadly dangerous for owners of electric pacemakers - the latter have a clear threshold level above which the electromagnetic radiation surrounding a person should not rise.

Devices that a person encounters in the course of his life mobile phones; radio transmitting antennas; radiotelephones of the DECT system; network wireless devices; Bluetooth devices; body scanners; babyphones; household electrical appliances; high voltage power lines.

How can you protect yourself from radio waves? The only one effective method- Stay away from them. The radiation dose decreases in proportion to the distance: the less, the farther from the emitter a person is. Appliances(drills, vacuum cleaners) generate el.magnetic fields around the power cord, provided that the wiring is illiterately installed. The greater the power of the device, the greater its impact. You can protect yourself by placing them as far away from people as possible. Appliances not in use must be unplugged.

Infrared radiation is also called "thermal" radiation, since infrared radiation from heated objects is perceived by human skin as a sensation of warmth. In this case, the wavelengths emitted by the body depend on the heating temperature: the higher the temperature, the shorter the wavelength and the higher the radiation intensity. The 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. Infrared radiation

The depth of penetration and, accordingly, the heating of the body by infrared radiation depends on the wavelength. Short-wave radiation is able to penetrate the body to a depth of several centimeters and heats the internal organs, while long-wave radiation is retained by the moisture contained in the tissues and increases the temperature of the integument of the body. Especially dangerous is the effect of intense infrared radiation on the brain - it can cause heat stroke. Unlike other types of radiation, such as X-ray, microwave and ultraviolet, infrared radiation of normal intensity does not negative impact on the body. Effect of infrared radiation on the body

Ultraviolet radiation is electromagnetic radiation invisible to the eye, located on the spectrum between visible and X-ray radiation. Ultraviolet Radiation The range of ultraviolet radiation reaching the Earth's surface is 400 - 280 nm, while shorter wavelengths from the Sun are absorbed in the stratosphere with the help of the ozone layer.

Properties of UV radiation chemical activity (accelerates the course of chemical reactions and biological processes) penetrating ability destruction of microorganisms, a beneficial effect on the human body (in small doses) the ability to cause luminescence of substances (their glow with different colors of emitted light)

Exposure to ultraviolet radiation Exposing the skin to ultraviolet radiation in excess of the skin's natural protective ability to tan leads to burns varying degrees. Ultraviolet radiation can lead to the formation of mutations (ultraviolet mutagenesis). The formation of mutations, in turn, can cause skin cancer, skin melanoma and premature aging. An effective remedy protection against ultraviolet radiation is provided by clothing and special sunscreens with an SPF number of more than 10. Ultraviolet radiation of the medium wave range (280-315 nm) is practically imperceptible to the human eye and is mainly absorbed by the corneal epithelium, which causes radiation damage - burns under intense irradiation cornea (electrophthalmia). This is manifested by increased lacrimation, photophobia, edema of the corneal epithelium. To protect the eyes, special goggles are used that block up to 100% of ultraviolet radiation and are transparent in the visible spectrum. For even shorter wavelengths, there is no material suitable for the transparency of the objective lenses, and reflective optics - concave mirrors - have to be used.

X-ray radiation - electromagnetic waves whose photon energy lies on the scale of electromagnetic waves between ultraviolet radiation and gamma radiation Use of x-rays in medicine The reason for the use of x-rays in diagnostics was their high penetrating power. In the early days of discovery, X-rays were mainly used to examine bone fractures and locate foreign bodies (such as bullets) in the human body. Currently, several diagnostic methods are used using x-rays.

Fluoroscopy After X-rays pass through the patient's body, the doctor observes a shadow image of the patient. A lead window should be installed between the screen and the doctor's eyes in order to protect the doctor from the harmful effects of x-rays. This method makes it possible to study the functional state of some organs. The disadvantages of this method are insufficient contrast images and relatively high doses of radiation received by the patient during the procedure. Fluorography They are used, as a rule, for a preliminary study of the condition of the internal organs of patients using low doses of X-rays. Radiography This is a method of examination using X-rays, during which the image is recorded on photographic film. X-ray photographs contain more detail and are therefore more informative. Can be saved for further analysis. The total radiation dose is less than that used in fluoroscopy.

X-rays are ionizing. It affects the tissues of living organisms and can cause radiation sickness, radiation burns, and malignant tumors. For this reason, protective measures must be taken when working with X-rays. It is believed that the damage is directly proportional to the absorbed dose of radiation. X-ray radiation is a mutagenic factor.

The effect of X-rays on the body X-rays have a high penetrating power; they are able to freely penetrate through the studied organs and tissues. The effect of X-rays on the body is also manifested by the fact that X-rays ionize the molecules of substances, which leads to a violation of the original structure of the molecular structure of cells. Thus, ions (positively or negatively charged particles) are formed, as well as molecules, which become active. These changes in one way or another can cause the development of radiation burns of the skin and mucous membranes, radiation sickness, as well as mutations, which leads to the formation of a tumor, including a malignant one. However, these changes can occur only if the duration and frequency of X-ray exposure to the body is significant. The more powerful the x-ray beam and the longer the exposure, the higher the risk of negative effects.

In modern radiology, devices are used that have a very small beam energy. It is believed that the risk of developing cancer after a single standard X-ray examination is extremely small and does not exceed 1 thousandth of a percent. In clinical practice, a very short period of time is used, provided that the potential benefit of obtaining data on the state of the body is much higher than its potential danger. Radiologists, as well as technicians and laboratory assistants, must adhere to mandatory protective measures. The doctor performing the manipulation puts on a special protective apron, which is a protective lead plate. In addition, radiologists have an individual dosimeter, and as soon as it detects that the radiation dose is high, the doctor is removed from work with X-rays. Thus, X-ray radiation, although it has potentially dangerous effects on the body, is safe in practice.

Gamma radiation - a type of electromagnetic radiation with an extremely short wavelength - less than 2·10−10 m has the highest penetrating power. This type of radiation can be blocked by thick lead or concrete slab. The danger of radiation lies in its ionizing radiation, interacting with atoms and molecules, which this effect turns into positively charged ions, thereby breaking chemical bonds molecules that make up living organisms, and causing biologically important changes.

Dose rate - shows what dose of radiation an object or a living organism will receive over a period of time. Unit of measurement - Sievert / hour. Annual effective equivalent doses, μSv / year Cosmic radiation 32 Exposure from building materials and on the ground 37 Internal exposure 37 Radon-222, radon-220 126 Medical procedures 169 Nuclear weapons testing 1.5 Nuclear energy 0.01 Total 400

Table of the results of a single exposure to gamma radiation on the human body, measured in sieverts.

The impact of radiation on a living organism causes various reversible and irreversible biological changes in it. And these changes are divided into two categories - somatic changes caused directly in humans, and genetic changes that occur in descendants. The severity of the effects of radiation on a person depends on how this effect occurs - immediately or in portions. Most organs have time to recover to some extent from radiation, so they can better tolerate a series of short-term doses, compared with the same total dose of radiation received at a time. The red bone marrow and organs of the hematopoietic system, the reproductive organs and the organs of vision are the most exposed to radiation Children are more exposed to radiation than adults. Most organs of an adult are not so exposed to radiation - these are the kidneys, liver, bladder, cartilaginous tissues.

Conclusions The types of electromagnetic radiation are considered in detail. It was found that infrared radiation at normal intensity does not adversely affect the body. X-ray radiation can cause radiation burns and malignant tumors. gamma radiation causes biologically important changes in the body.

Thanks for attention

Lesson Objectives:

Lesson type:

Conduct form: lecture with presentation

Karaseva Irina Dmitrievna, 17.12.2017

2492 287

Development content

Lesson summary on the topic:

Types of radiation. Electromagnetic wave scale

Lesson designed

teacher of the State Institution of the LPR "LOUSOSH No. 18"

Karaseva I.D.

Lesson Objectives: consider the scale of electromagnetic waves, characterize the waves of different frequency ranges; show the role of various types of radiation in human life, the impact of various types of radiation on a person; systematize the material on the topic and deepen students' knowledge of electromagnetic waves; develop oral speech students, creative skills of students, logic, memory; cognitive abilities; to form students' interest in the study of physics; to cultivate accuracy, hard work.

Lesson type: a lesson in the formation of new knowledge.

Conduct form: lecture with presentation

Equipment: computer, multimedia projector, presentation “Types of radiation.

Scale of electromagnetic waves»

During the classes

Organizing time.

Motivation of educational and cognitive activity.

The universe is an ocean of electromagnetic radiation. People live in it, for the most part, not noticing the waves penetrating the surrounding space. Warming by the fireplace or lighting a candle, a person forces the source of these waves to work, without thinking about their properties. But knowledge is power: having discovered the nature of electromagnetic radiation, mankind during the 20th century mastered and put to its service its most diverse types.

Setting the topic and objectives of the lesson.

Today we will make a journey along the scale of electromagnetic waves, consider the types of electromagnetic radiation of different frequency ranges. Write down the topic of the lesson: “Types of radiation. Scale of electromagnetic waves» (Slide 1)

We will study each radiation according to the following generalized plan (Slide 2).Generalized plan for studying radiation:

1. Range name

2. Wavelength

3. Frequency

4. Who was discovered

5. Source

6. Receiver (indicator)

7. Application

8. Action on a person

During the study of the topic, you must complete the following table:

Table "Scale of electromagnetic radiation"

Name radiation	Wavelength	Frequency	Who was open	A source	Receiver	Application	Action on a person

Presentation of new material.

(Slide 3)

The length of electromagnetic waves is very different: from values ​​​​of the order of 10 13 m (low frequency vibrations) up to 10 -10 m ( -rays). Light is an insignificant part of the wide spectrum of electromagnetic waves. Nevertheless, it was during the study of this small part of the spectrum that other radiations with unusual properties.
It is customary to allocate low frequency radiation, radio emission, infrared rays, visible light, ultraviolet rays, X-rays And -radiation. The shortest - radiation emits atomic nuclei.

There is no fundamental difference between the individual radiations. All of them are electromagnetic waves generated by charged particles. Electromagnetic waves are detected, ultimately, by their action on charged particles . In a vacuum, radiation of any wavelength travels at a speed of 300,000 km/s. The boundaries between individual areas of the radiation scale are very arbitrary.

(Slide 4)

Emissions of various wavelengths differ from each other in the way they receiving(antenna radiation, thermal radiation, radiation during deceleration of fast electrons, etc.) and methods of registration.

All of the listed types of electromagnetic radiation are also generated by space objects and are successfully studied with the help of rockets, artificial earth satellites and spacecraft. First of all, this applies to X-ray and radiation that is strongly absorbed by the atmosphere.

Quantitative differences in wavelengths lead to significant qualitative differences.

Radiations of different wavelengths differ greatly from each other in terms of their absorption by matter. Shortwave radiation (X-ray and especially rays) are weakly absorbed. Substances that are opaque to optical wavelengths are transparent to these radiations. The reflection coefficient of electromagnetic waves also depends on the wavelength. But the main difference between longwave and shortwave radiation is that shortwave radiation reveals the properties of particles.

Let's consider each radiation.

(Slide 5)

low frequency radiation occurs in the frequency range from 3 · 10 -3 to 3 10 5 Hz. This radiation corresponds to a wavelength of 10 13 - 10 5 m. The radiation of such relatively low frequencies can be neglected. The source of low-frequency radiation are alternators. They are used in melting and hardening of metals.

(Slide 6)

radio waves occupy the frequency range 3·10 5 - 3·10 11 Hz. They correspond to a wavelength of 10 5 - 10 -3 m. radio waves, as well as low frequency radiation is alternating current. Also, the source is a radio frequency generator, stars, including the Sun, galaxies and metagalaxies. The indicators are the Hertz vibrator, oscillatory circuit.

Large frequency radio waves compared to low-frequency radiation leads to a noticeable radiation of radio waves into space. This allows them to be used to transmit information over various distances. Speech, music (broadcasting), telegraph signals (radio communication), images of various objects (radar) are transmitted.

Radio waves are used to study the structure of matter and the properties of the medium in which they propagate. The study of radio emission from space objects is the subject of radio astronomy. In radiometeorology, processes are studied according to the characteristics of received waves.

(Slide 7)

Infrared radiation occupies the frequency range 3 10 11 - 3.85 10 14 Hz. They correspond to a wavelength of 2 10 -3 - 7.6 10 -7 m.

Infrared radiation was discovered in 1800 by astronomer William Herschel. Studying the rise in temperature of a thermometer heated by visible light, Herschel found the greatest heating of the thermometer outside the visible light region (beyond the red region). Invisible radiation, given its place in the spectrum, was called infrared. The source of infrared radiation is the radiation of molecules and atoms under thermal and electrical influences. A powerful source of infrared radiation is the Sun, about 50% of its radiation lies in the infrared region. Infrared radiation accounts for a significant proportion (from 70 to 80%) of the radiation energy of incandescent lamps with a tungsten filament. Infrared radiation is emitted by an electric arc and various gas discharge lamps. The radiation of some lasers lies in the infrared region of the spectrum. Indicators of infrared radiation are photo and thermistors, special photo emulsions. Infrared radiation is used for drying wood, food products and various paint and varnish coatings ( infrared heating), for signaling in case of poor visibility, makes it possible to use optical devices that allow you to see in the dark, as well as when remote control. Infra-red beams are used to aim projectiles and missiles at the target, to detect a camouflaged enemy. These rays make it possible to determine the difference in temperatures of individual sections of the surface of the planets, the structural features of the molecules of a substance (spectral analysis). Infrared photography is used in biology in the study of plant diseases, in medicine in the diagnosis of skin and vascular diseases, in forensics in the detection of fakes. When exposed to a person, it causes an increase in the temperature of the human body.

(Slide 8)

Visible radiation - the only range of electromagnetic waves perceived by the human eye. Light waves occupy a fairly narrow range: 380 - 670 nm ( \u003d 3.85 10 14 - 8 10 14 Hz). The source of visible radiation is valence electrons in atoms and molecules that change their position in space, as well as free charges, moving rapidly. This part of the spectrum gives a person maximum information about the world around him. By their own physical properties it is similar to other ranges of the spectrum, being only a small part of the spectrum of electromagnetic waves. Radiation having different wavelengths (frequencies) in the visible range has different physiological effects on the retina of the human eye, causing a psychological sensation of light. Color is not a property of an electromagnetic light wave in itself, but a manifestation of the electrochemical action of the human physiological system: eyes, nerves, brain. Approximately, seven primary colors can be distinguished by the human eye in the visible range (in ascending order of radiation frequency): red, orange, yellow, green, blue, indigo, violet. Remembering the sequence of the primary colors of the spectrum is facilitated by a phrase, each word of which begins with the first letter of the name of the primary color: "Every Hunter Wants to Know Where the Pheasant Sits." Visible radiation can influence the course of chemical reactions in plants (photosynthesis) and in animal and human organisms. Visible radiation is emitted by individual insects (fireflies) and some deep-sea fish due to chemical reactions in the body. The absorption of carbon dioxide by plants as a result of the process of photosynthesis and the release of oxygen contributes to the maintenance of biological life on Earth. Visible radiation is also used to illuminate various objects.

Light is the source of life on Earth and at the same time the source of our ideas about the world around us.

(Slide 9)

Ultraviolet radiation, electromagnetic radiation invisible to the eye, occupying the spectral region between visible and X-ray radiation within the wavelengths of 3.8 ∙10 -7 - 3 ∙10 -9 m ( \u003d 8 * 10 14 - 3 * 10 16 Hz). Ultraviolet radiation was discovered in 1801 by the German scientist Johann Ritter. By studying the blackening of silver chloride under the action of visible light, Ritter found that silver blackens even more effectively in the region beyond the violet end of the spectrum, where there is no visible radiation. The invisible radiation that caused this blackening was called ultraviolet.

The source of ultraviolet radiation is the valence electrons of atoms and molecules, also rapidly moving free charges.

Radiation heated up to temperatures - 3000 K solids contains a significant proportion of continuous spectrum ultraviolet radiation, the intensity of which increases with increasing temperature. A more powerful source of ultraviolet radiation is any high-temperature plasma. For various applications of ultraviolet radiation, mercury, xenon, and other gas discharge lamps are used. Natural sources of ultraviolet radiation - the Sun, stars, nebulae and other space objects. However, only the long-wavelength part of their radiation (  290 nm) reaches the earth's surface. For registration of ultraviolet radiation at

 = 230 nm, ordinary photographic materials are used; in the shorter wavelength region, special low-gelatin photographic layers are sensitive to it. Photoelectric receivers are used that use the ability of ultraviolet radiation to cause ionization and the photoelectric effect: photodiodes, ionization chambers, photon counters, photomultipliers.

In small doses, ultraviolet radiation has a beneficial, healing effect on a person, activating the synthesis of vitamin D in the body, and also causing sunburn. A large dose of ultraviolet radiation can cause skin burns and cancerous growths (80% curable). In addition, excessive ultraviolet radiation weakens immune system organism, contributing to the development of certain diseases. Ultraviolet radiation also has a bactericidal effect: under the influence of this radiation, pathogenic bacteria die.

Ultraviolet radiation is used in fluorescent lamps, in forensics (forgery of documents is detected from the pictures), in art history (with the help of ultraviolet rays it is possible to detect in the paintings not visible to the eye traces of restoration). Practically does not pass ultra-violet radiation a window glass since. it is absorbed by iron oxide, which is part of the glass. For this reason, even on a hot sunny day, you cannot tan in a room with closed window.

The human eye does not see ultraviolet radiation, because. The cornea of ​​the eye and the eye lens absorb ultraviolet light. Some animals can see ultraviolet radiation. For example, a dove is guided by the Sun even in cloudy weather.

(Slide 10)

x-ray radiation - this is electromagnetic ionizing radiation occupying the spectral region between gamma and ultraviolet radiation within wavelengths from 10 -12 - 10 -8 m (frequencies 3 * 10 16 - 3-10 20 Hz). X-ray radiation was discovered in 1895 by the German physicist W. K. Roentgen. The most common X-ray source is the X-ray tube, in which electrons accelerated by an electric field bombard a metal anode. X-rays can be obtained by bombarding a target with high-energy ions. Some radioactive isotopes, synchrotrons - electron accumulators can also serve as sources of X-ray radiation. The natural sources of X-rays are the Sun and other space objects.

Images of objects in x-rays are obtained on a special x-ray photographic film. X-ray radiation can be recorded using an ionization chamber, a scintillation counter, secondary electron or channel electron multipliers, and microchannel plates. Due to its high penetrating power, X-ray radiation is used in X-ray diffraction analysis (study of the structure crystal lattice), in the study of the structure of molecules, the detection of defects in samples, in medicine (X-rays, fluorography, the treatment of cancer), in flaw detection (detection of defects in castings, rails), in art history (detection of ancient paintings hidden under a layer of late painting), in astronomy (in the study of x-ray sources), forensics. A large dose of X-ray radiation leads to burns and changes in the structure of human blood. The creation of X-ray receivers and their placement on space stations made it possible to detect the X-ray emission of hundreds of stars, as well as the shells of supernovae and entire galaxies.

(Slide 11)

Gamma radiation - short-wave electromagnetic radiation, occupying the entire frequency range  \u003d 8 10 14 - 10 17 Hz, which corresponds to wavelengths  \u003d 3.8 10 -7 - 3 10 -9 m. Gamma radiation was discovered by the French scientist Paul Villars in 1900.

Studying the radiation of radium in a strong magnetic field, Villars discovered short-wave electromagnetic radiation, which does not deviate, like light, magnetic field. It was called gamma radiation. Gamma radiation is associated with nuclear processes, the phenomena of radioactive decay that occur with certain substances, both on Earth and in space. Gamma radiation can be recorded using ionization and bubble chambers, as well as using special photographic emulsions. They are used in the study of nuclear processes, in flaw detection. Gamma radiation has a negative effect on humans.

(Slide 12)

So, low frequency radiation, radio waves, infrared radiation, visible radiation, ultraviolet radiation, X-rays, radiation are different kinds electromagnetic radiation.

If you mentally decompose these types in terms of increasing frequency or decreasing wavelength, you get a wide continuous spectrum - the scale of electromagnetic radiation (teacher shows the scale). Hazardous types of radiation include: gamma radiation, x-rays and ultraviolet radiation, the rest are safe.

The division of electromagnetic radiation into ranges is conditional. There is no clear boundary between regions. The names of the regions have developed historically, they only serve as a convenient means of classifying radiation sources.

(Slide 13)

All ranges of the electromagnetic radiation scale have general properties:

the physical nature of all radiation is the same

all radiation propagates in vacuum with the same speed, equal to 3 * 10 8 m / s

all radiations exhibit common wave properties (reflection, refraction, interference, diffraction, polarization)

5. Summing up the lesson

At the end of the lesson, students complete the work on the table.

(Slide 14)

Output:

The entire scale of electromagnetic waves is evidence that all radiation has both quantum and wave properties.

Quantum and wave properties in this case do not exclude, but complement each other.

The wave properties are more pronounced at low frequencies and less pronounced at high frequencies. Conversely, quantum properties are more pronounced at high frequencies and less pronounced at low frequencies.

The shorter the wavelength, the more pronounced the quantum properties, and the longer the wavelength, the more pronounced the wave properties.

All this confirms the law of dialectics (transition of quantitative changes into qualitative ones).

Abstract (learn), fill in the table

the last column (the effect of EMP on a person) and

prepare a report on the use of EMR

Development content

GU LPR "LOUSOSH No. 18"

Lugansk

Karaseva I.D.

GENERALIZED RADIATION STUDY PLAN

1. Range name.

2. Wavelength

3. Frequency

4. Who was discovered

5. Source

6. Receiver (indicator)

7. Application

8. Action on a person

TABLE "SCALE OF ELECTROMAGNETIC WAVES"

Radiation name

Wavelength

Frequency

Who opened

A source

Receiver

Application

Action on a person

Radiations differ from each other:

• according to the method of obtaining;
• registration method.

Quantitative differences in wavelengths lead to significant qualitative differences; they are absorbed differently by matter (short-wave radiation - X-ray and gamma radiation) - are absorbed weakly.

Shortwave radiation reveals the properties of particles.

Low frequency vibrations

Wave length (m)

10 13 - 10 5

Frequency Hz)

3 · 10 -3 - 3 · 10 5

A source

Rheostatic alternator, dynamo,

hertz vibrator,

generators in electrical networks(50 Hz)

Machine generators of increased (industrial) frequency (200 Hz)

Telephone networks (5000Hz)

Sound generators (microphones, loudspeakers)

Receiver

Electrical appliances and motors

Discovery history

Oliver Lodge (1893), Nikola Tesla (1983)

Application

Cinema, broadcasting (microphones, loudspeakers)

radio waves

Wavelength(m)

Frequency Hz)

10 5 - 10 -3

A source

3 · 10 5 - 3 · 10 11

Oscillatory circuit

Macroscopic vibrators

Stars, galaxies, metagalaxies

Receiver

Discovery history

Sparks in the gap of the receiving vibrator (Hertz vibrator)

The glow of a gas discharge tube, coherer

B. Feddersen (1862), G. Hertz (1887), A.S. Popov, A.N. Lebedev

Application

Extra long- Radio navigation, radiotelegraph communication, transmission of weather reports

Long– Radiotelegraph and radiotelephone communications, radio broadcasting, radio navigation

Medium- Radiotelegraphy and radiotelephony radio broadcasting, radio navigation

Short- amateur radio

VHF- space radio communications

DMV- television, radar, radio relay communication, cellular telephone communication

SMV- radar, radio relay communication, astronavigation, satellite television

IIM- radar

Infrared radiation

Wavelength(m)

2 · 10 -3 - 7,6∙10 -7

Frequency Hz)

3∙10 11 - 3,85∙10 14

A source

Any heated body: a candle, a stove, a water heating battery, an electric incandescent lamp

A person emits electromagnetic waves with a length of 9 · 10 -6 m

Receiver

Thermoelements, bolometers, photocells, photoresistors, photographic films

Discovery history

W. Herschel (1800), G. Rubens and E. Nichols (1896),

Application

In forensics, photographing terrestrial objects in fog and darkness, binoculars and sights for shooting in the dark, heating the tissues of a living organism (in medicine), drying wood and painted car bodies, alarms for the protection of premises, an infrared telescope.

Visible radiation

Wavelength(m)

6,7∙10 -7 - 3,8 ∙10 -7

Frequency Hz)

4∙10 14 - 8 ∙10 14

A source

Sun, incandescent lamp, fire

Receiver

Eye, photographic plate, photocells, thermoelements

Discovery history

M. Melloni

Application

Vision

biological life

Ultraviolet radiation

Wavelength(m)

3,8 ∙10 -7 - 3∙10 -9

Frequency Hz)

8 ∙ 10 14 - 3 · 10 16

A source

Included in sunlight

Discharge lamps with quartz tube

Radiated by all solids whose temperature is more than 1000 ° C, luminous (except mercury)

Receiver

photocells,

photomultipliers,

Luminescent substances

Discovery history

Johann Ritter, Leiman

Application

Industrial electronics and automation,

fluorescent lamps,

Textile production

Air sterilization

Medicine, cosmetology

x-ray radiation

Wavelength(m)

10 -12 - 10 -8

Frequency Hz)

3∙10 16 - 3 · 10 20

A source

Electronic X-ray tube (voltage at the anode - up to 100 kV, cathode - incandescent filament, radiation - high energy quanta)

solar corona

Receiver

Camera roll,

Glow of some crystals

Discovery history

W. Roentgen, R. Milliken

Application

Diagnosis and treatment of diseases (in medicine), Defectoscopy (control of internal structures, welds)

Gamma radiation

Wavelength(m)

3,8 · 10 -7 - 3∙10 -9

Frequency Hz)

8∙10 14 - 10 17

Energy(EV)

9,03 10 3 – 1, 24 10 16 Ev

A source

radioactive atomic nuclei, nuclear reactions, processes of transformation of matter into radiation

Receiver

counters

Discovery history

Paul Villars (1900)

Application

Defectoscopy

Process control

Research of nuclear processes

Therapy and diagnostics in medicine

GENERAL PROPERTIES OF ELECTROMAGNETIC RADIATIONS

physical nature

all radiation is the same

all radiation propagates

in a vacuum at the same speed,

equal to the speed of light

all radiations are detected

general wave properties

polarization

reflection

refraction

diffraction

interference

• The entire scale of electromagnetic waves is evidence that all radiation has both quantum and wave properties.
• Quantum and wave properties in this case do not exclude, but complement each other.
• The wave properties are more pronounced at low frequencies and less pronounced at high frequencies. Conversely, quantum properties are more pronounced at high frequencies and less pronounced at low frequencies.
• The shorter the wavelength, the more pronounced the quantum properties, and the longer the wavelength, the more pronounced the wave properties.

• § 68 (read)
• fill in the last column of the table (the effect of EMP on a person)
• prepare a report on the use of EMR

Topic: “Types of radiation. Sources of light. Scale of electromagnetic waves.

Purpose: to establish common properties and differences on the topic "Electromagnetic radiation"; compare different types of radiation.

Equipment: presentation "Scale of electromagnetic waves".

During the classes.

I. Organizational moment.

II. Knowledge update.

Frontal conversation.

What wave is light? What is coherence? What waves are called coherent? What is called wave interference, and under what conditions does this phenomenon occur? What is the path difference? Optical travel difference? How are the conditions for the formation of interference maxima and minima written? The use of interference in technology. What is the diffraction of light? Formulate Huygens' principle; the Huygens-Fresnel principle. Name the diffraction patterns from various obstacles. What is a diffraction grating? Where is a diffraction grating used? What is light polarization? What are polaroids used for?

III. Learning new material.

The universe is an ocean of electromagnetic radiation. People live in it, for the most part, not noticing the waves penetrating the surrounding space. Warming by the fireplace or lighting a candle, a person forces the source of these waves to work, without thinking about their properties. But knowledge is power: having discovered the nature of electromagnetic radiation, mankind during the 20th century mastered and put to its service its most diverse types.

We know that the length of electromagnetic waves is very different. Light is an insignificant part of the wide spectrum of electromagnetic waves. In the study of this small part of the spectrum, other radiations with unusual properties were discovered. It is customary to distinguish low-frequency radiation, radio radiation, infrared rays, visible light, ultraviolet rays, x-rays and z-radiation.

More than a hundred years, in fact, from the beginning of the 19th century, the discovery of more and more new waves continued. The unity of the waves was proved by Maxwell's theory. Before him, many waves were considered as phenomena of a different nature. Consider the scale of electromagnetic waves, which is divided into ranges by frequency, but also by the method of radiation. There are no strict boundaries between the individual ranges of electromagnetic waves. At the boundaries of the ranges, the type of wave is set according to the method of its radiation, i.e., an electromagnetic wave from the same frequency can in one case or another be attributed to different kind waves. For example, radiation with a wavelength of 100 microns can be referred to as radio waves or infrared waves. The exception is visible light.

Types of radiation.

type of radiation	wavelength, frequency	sources	properties	application	propagation speed in vacuum
low frequency	0 to 2104 Hz from 1.5 104 to ∞ m.	alternators.	Reflection, absorption, refraction.	They are used in melting and hardening of metals.
radio waves		alternating current. radio frequency generator, stars, including the Sun, galaxies and metagalaxies.	interference, diffraction.	To transmit information over various distances. Speech, music (broadcasting), telegraph signals (radio communication), images of various objects (radar) are transmitted.
infrared	3*1011- 3.85*1014 Hz. 780nm -1mm.	Radiation of molecules and atoms under thermal and electrical influences. Powerful source of infrared radiation - the Sun	reflection, absorption, refraction, interference, diffraction.
	3.85 1014- 7.89 1014 Hz	Valence electrons in atoms and molecules that change their position in space, as well as free charges moving at an accelerated rate.	reflection, absorption, refraction, interference, diffraction.	The absorption of carbon dioxide by plants as a result of the process of photosynthesis and the release of oxygen contributes to the maintenance of biological life on Earth. Visible radiation is also used to illuminate various objects.
ultraviolet	0.2 µm to 0.38 µm 8*1014-3*1016Hz	valence electrons of atoms and molecules, also accelerated moving free charges. Discharge lamps with quartz tubes (quartz lamps). Solids with T> 1000 ° C, as well as luminous mercury vapor. High temperature plasma.	High chemical activity (decomposition of silver chloride, glow of zinc sulfide crystals), invisible, high penetrating power, kills microorganisms, in small doses it has a beneficial effect on the human body (sunburn), but in large doses it has a negative biological effect: changes in cell development and metabolism substances acting on the eyes.	The medicine. Lumines cent lamps. Criminalistics (according to discover forgeries documents). Art history (with ultraviolet rays can be found in pictures traces of restoration invisible to the eye)
x-ray	10-12- 10-8 m (frequency 3*1016-3-1020 Hz	Some radioactive isotopes, electron storage synchrotrons. The natural sources of X-rays are the Sun and other space objects	High penetrating power. reflection, absorption, refraction, interference, diffraction.	X-ray structure- analysis, medicine, criminology, art history.
Gamma radiation		Nuclear processes.	reflection, absorption, refraction, interference, diffraction.	In the study of nuclear processes, in flaw detection.

Similarities and differences.

General properties and characteristics of electromagnetic waves.

Properties	Characteristics
Distribution in space over time	The speed of electromagnetic waves in vacuum is constant and equal to approximately 300,000 km/s
All waves are absorbed by matter	Various absorption coefficients
All waves at the interface between two media are partially reflected, partially refracted.	Laws of reflection and refraction. Reflection coefficients for different media and different waves.
All electromagnetic radiation exhibits the properties of waves: they add up, go around obstacles. Several waves can simultaneously exist in the same region of space	The principle of superposition. For coherent sources, the rules for determining the maxima. Huygens-Fresnel principle. Waves do not interact with each other
Complex electromagnetic waves, when interacting with matter, are decomposed into a spectrum - dispersion.	Dependence of the refractive index of the medium on the frequency of the wave. Wave speed in matter depends on the refractive index of the medium v ​​= c/n
Waves of different intensity	Radiation Flux Density

As the wavelength decreases, quantitative differences in wavelengths lead to significant qualitative differences. Radiations of different wavelengths differ greatly from each other in terms of their absorption by matter. Shortwave radiations are absorbed weakly. Substances that are opaque to optical wavelengths are transparent to these radiations. The reflection coefficient of electromagnetic waves also depends on the wavelength. But the main difference between longwave and shortwave radiation is that shortwave radiation reveals the properties of particles.

1 Low frequency radiation

Low-frequency radiation occurs in the frequency range from 0 to 2104 Hz. This radiation corresponds to a wavelength from 1.5 104 to ∞ m. The radiation of such relatively low frequencies can be neglected. The source of low-frequency radiation are alternators. They are used in melting and hardening of metals.

2 Radio waves

Radio waves occupy the frequency range 2 * 104-109 Hz. They correspond to a wavelength of 0.3-1.5 * 104 m. The source of radio waves, as well as low-frequency radiation, is alternating current. Also, the source is a radio frequency generator, stars, including the Sun, galaxies and metagalaxies. The indicators are the Hertz vibrator, the oscillatory circuit.

The high frequency of radio waves, in comparison with low-frequency radiation, leads to a noticeable radiation of radio waves into space. This allows them to be used to transmit information over various distances. Speech, music (broadcasting), telegraph signals (radio communication), images of various objects (radar) are transmitted. Radio waves are used to study the structure of matter and the properties of the medium in which they propagate. The study of radio emission from space objects is the subject of radio astronomy. In radiometeorology, processes are studied according to the characteristics of received waves.

3 Infrared (IR)

Infrared radiation occupy the frequency range 3 * 1011 - 3.85 * 1014 Hz. They correspond to a wavelength of 780nm -1mm. Infrared radiation was discovered in 1800 by astronomer William Hershl. Studying the rise in temperature of a thermometer heated by visible light, Herschel found the greatest heating of the thermometer outside the visible light region (beyond the red region). Invisible radiation, given its place in the spectrum, was called infrared. The source of infrared radiation is the radiation of molecules and atoms under thermal and electrical influences. A powerful source of infrared radiation is the Sun, about 50% of its radiation lies in the infrared region. Infrared radiation accounts for a significant proportion (from 70 to 80%) of the radiation energy of incandescent lamps with a tungsten filament. Infrared radiation is emitted by an electric arc and various gas discharge lamps. The radiation of some lasers lies in the infrared region of the spectrum. Indicators of infrared radiation are photo and thermistors, special photo emulsions. Infrared radiation is used for drying wood, food products and various paint and varnish coatings (infrared heating), for signaling in case of poor visibility, makes it possible to use optical devices that allow you to see in the dark, as well as with remote control. Infra-red beams are used to aim projectiles and missiles at the target, to detect a camouflaged enemy. These rays make it possible to determine the difference in temperatures of individual sections of the surface of the planets, the structural features of the molecules of a substance (spectral analysis). Infrared photography is used in biology in the study of plant diseases, in medicine in the diagnosis of skin and vascular diseases, in forensics in the detection of fakes. When exposed to a person, it causes an increase in the temperature of the human body.

Visible radiation (light)

Visible radiation is the only range of electromagnetic waves perceived by the human eye. Light waves occupy a rather narrow range: 380-780 nm (ν = 3.85 1014-7.89 1014 Hz). The source of visible radiation is valence electrons in atoms and molecules that change their position in space, as well as free charges moving at an accelerated rate. This part of the spectrum gives a person maximum information about the world around him. In terms of its physical properties, it is similar to other ranges of the spectrum, being only a small part of the spectrum of electromagnetic waves. Radiation having different wavelengths (frequencies) in the visible range has different physiological effects on the retina of the human eye, causing a psychological sensation of light. Color is not a property of an electromagnetic light wave in itself, but a manifestation of the electrochemical action of the human physiological system: eyes, nerves, brain. Approximately, seven primary colors can be distinguished by the human eye in the visible range (in ascending order of radiation frequency): red, orange, yellow, green, blue, indigo, violet. Remembering the sequence of the primary colors of the spectrum is facilitated by a phrase, each word of which begins with the first letter of the name of the primary color: "Every Hunter Wants to Know Where the Pheasant Sits." Visible radiation can influence the course of chemical reactions in plants (photosynthesis) and in animal and human organisms. Visible radiation is emitted by individual insects (fireflies) and some deep-sea fish due to chemical reactions in the body. The absorption of carbon dioxide by plants as a result of the process of photosynthesis, the release of oxygen contributes to the maintenance of biological life on Earth. Visible radiation is also used to illuminate various objects.

Light is the source of life on Earth and at the same time the source of our ideas about the world around us.

5. Ultraviolet radiation

Ultraviolet radiation, electromagnetic radiation invisible to the eye, occupying the spectral region between visible and X-ray radiation within the wavelengths of 10 - 380 nm (ν = 8 * 1014-3 * 1016 Hz). Ultraviolet radiation was discovered in 1801 by the German scientist Johann Ritter. By studying the blackening of silver chloride under the action of visible light, Ritter found that silver blackens even more effectively in the region beyond the violet end of the spectrum, where there is no visible radiation. The invisible radiation that caused this blackening was called ultraviolet. The source of ultraviolet radiation is the valence electrons of atoms and molecules, as well as accelerated moving free charges. The radiation of solids heated to temperatures of - 3000 K contains a significant fraction of continuous spectrum ultraviolet radiation, the intensity of which increases with increasing temperature. A more powerful source of ultraviolet radiation is any high-temperature plasma. For various applications of ultraviolet radiation, mercury, xenon, and other gas discharge lamps are used. Natural sources of ultraviolet radiation - the Sun, stars, nebulae and other space objects. However, only the long-wavelength part of their radiation (λ>290 nm) reaches the earth's surface. To register ultraviolet radiation at λ = 230 nm, ordinary photographic materials are used; in the shorter wavelength region, special low-gelatin photographic layers are sensitive to it. Photoelectric receivers are used that use the ability of ultraviolet radiation to cause ionization and the photoelectric effect: photodiodes, ionization chambers, photon counters, photomultipliers.

In small doses, ultraviolet radiation has a beneficial, healing effect on a person, activating the synthesis of vitamin D in the body, and also causing sunburn. A large dose of ultraviolet radiation can cause skin burns and cancerous growths (80% curable). In addition, excessive ultraviolet radiation weakens the body's immune system, contributing to the development of certain diseases. Ultraviolet radiation also has a bactericidal effect: pathogenic bacteria die under the influence of this radiation.

Ultraviolet radiation is used in fluorescent lamps, in forensics (forgery of documents is detected from the pictures), in art history (with the help of ultraviolet rays, traces of restoration that are not visible to the eye can be detected in the paintings). Window glass practically does not transmit ultraviolet radiation, since it is absorbed by iron oxide, which is part of the glass. For this reason, even on a hot sunny day, you cannot sunbathe in a room with the window closed. The human eye does not see ultraviolet radiation, because the cornea of ​​​​the eye and the eye lens absorb ultraviolet radiation. Some animals can see ultraviolet radiation. For example, a dove is guided by the Sun even in cloudy weather.

6. X-rays

X-ray radiation is an electromagnetic ionizing radiation that occupies the spectral region between gamma and ultraviolet radiation within wavelengths from 10-12-10-8 m (frequency 3 * 1016-3-1020 Hz). X-ray radiation was discovered in 1895 by a German physicist. The most common X-ray source is the X-ray tube, in which electrons accelerated by an electric field bombard a metal anode. X-rays can be obtained by bombarding a target with high-energy ions. Certain radioactive isotopes and electron storage synchrotrons can also serve as X-ray sources. The natural sources of X-rays are the Sun and other space objects

Images of objects in x-rays are obtained on a special x-ray film. X-ray radiation can be recorded using an ionization chamber, a scintillation counter, secondary electron or channel electron multipliers, microchannel plates. Due to its high penetrating power, X-rays are used in X-ray diffraction analysis (the study of the structure of the crystal lattice), in the study of the structure of molecules, the detection of defects in samples, in medicine (X-rays, fluorography, cancer treatment), in flaw detection (detection of defects in castings, rails) , in art history (the discovery of ancient paintings hidden under a layer of late painting), in astronomy (when studying X-ray sources), and forensic science. A large dose of X-ray radiation leads to burns and changes in the structure of human blood. The creation of X-ray receivers and their placement on space stations made it possible to detect the X-ray emission of hundreds of stars, as well as the shells of supernovae and entire galaxies.

7. Gamma radiation (γ - rays)

Gamma radiation - short-wave electromagnetic radiation, occupying the entire frequency range ν\u003e Z * 1020 Hz, which corresponds to wavelengths λ<10-12 м. Гамма излучение было открыто французским ученым Полем Вилларом в 1900 году. Изучая излучение радия в сильном магнитном поле, Виллар обнаружил коротковолновое электромагнитное излучение, не отклоняющееся, как и свет, магнитным полем. Оно было названо Iгамма излучением. Гамма излучение связано с ядерными процессами, явлениями радиоактивного распада, происходящими с некоторыми веществами, как на Земле, так и в космосе. Гамма излучение можно регистрировать с помощью ионизационных и пузырьковых камер, а также с помощью специальных фотоэмульсий. Используются при исследовании ядерных процессов, в дефектоскопии. Гамма излучение отрицательно воздействует на человека.

IV. Consolidation of the studied material.

Low frequency radiation, radio waves, infrared radiation, visible radiation, ultraviolet radiation, X-rays, γ-rays are various types of electromagnetic radiation.

If you mentally decompose these types in terms of increasing frequency or decreasing wavelength, you get a wide continuous spectrum - a scale of electromagnetic radiation (the teacher shows the scale). The division of electromagnetic radiation into ranges is conditional. There is no clear boundary between regions. The names of the regions have developed historically, they only serve as a convenient means of classifying radiation sources.

All ranges of the electromagnetic radiation scale have common properties:

The physical nature of all radiation is the same. All radiation propagates in vacuum with the same speed equal to 3 * 108 m / s. All radiation exhibits common wave properties (reflection, refraction, interference, diffraction, polarization).

BUT). Complete tasks to determine the type of radiation and its physical nature.

1. Do burning wood emit electromagnetic waves? Non-burning? (Emit. Burning - infrared and visible rays, and non-burning - infrared).

2. What explains the white color of snow, the black color of soot, the green color of leaves, the red color of paper? (Snow reflects all waves, soot absorbs everything, leaves reflect green, paper red).

3. What role does the atmosphere play in life on Earth? (UV protection).

4. Why does dark glass protect the welder's eyes? (Glass does not transmit ultraviolet light, but dark glass and bright visible flame radiation that occurs during welding).

5. When satellites or spaceships pass through the ionized layers of the atmosphere, they become sources of X-rays. Why? (In the atmosphere, fast moving electrons hit the walls of moving objects and X-rays are produced.)

6. What is microwave radiation and where is it used? (Super high frequency radiation, microwave ovens).

B). Verification test.

1. Infrared radiation has a wavelength:

A. Less than 4 * 10-7 m. B. More than 7.6 * 10-7 m C. Less than 10 -8 m

2. Ultraviolet radiation:

A. Occurs during a sharp deceleration of fast electrons.

B. Intensively emitted by bodies heated to a high temperature.

B. Emitted by any heated body.

3. What is the wavelength range of visible radiation?

A. 4*10-7- 7.5*10-7 m. B. 4*10-7- 7.5*10-7 cm. C. 4*10-7- 7.5*10-7 mm .

4. The greatest passing ability has:

A. Visible radiation B. Ultraviolet radiation C. X-ray radiation

5. An image of an object in the dark is obtained using:

A. Ultraviolet radiation. B. X-ray radiation.

B. Infrared radiation.

6. Who first discovered γ-radiation?

A. Roentgen B. Villar W. Herschel

7. How fast does infrared radiation travel?

A. More than 3*108 m/s B. Less than 3*10 8 m/s C. 3*108 m/s

8. X-ray radiation:

A. Occurs during a sharp deceleration of fast electrons

B. Emitted by solids heated to a high temperature

B. Emitted by any heated body

9. What kind of radiation is used in medicine?

Infrared radiation Ultraviolet radiation Visible radiation X-ray radiation

A. 1.2.4 B. 1.3 C. All radiation

10. Ordinary glass practically does not let through:

A. Visible radiation. B. Ultraviolet radiation. C. Infrared Radiation Correct answers: 1(B); 2 (B); 3(A); 4(B); 5(B); 6(B); 7(B); 8(A); 9(A); 10(B).

Grading scale: 5 - 9-10 tasks; 4 - 7-8 tasks; 3 - 5-6 tasks.

IV. Summary of the lesson.

V. Homework: §80,86.