Scale of electromagnetic radiation properties. Electromagnetic radiation scale

The lengths of electromagnetic waves that can be registered by devices lie in a very wide range. All these waves have common properties: absorption, reflection, interference, diffraction, dispersion. These properties can, however, manifest themselves in different ways. Wave sources and receivers are different.

radio waves

ν \u003d 10 5 - 10 11 Hz, λ \u003d 10 -3 -10 3 m.

Obtained using oscillatory circuits and macroscopic vibrators. Properties. Radio waves of different frequencies and with different wavelengths are absorbed and reflected by media in different ways. Application Radio communication, television, radar. In nature, radio waves are emitted by various extraterrestrial sources (galactic nuclei, quasars).

Infrared radiation (thermal)

ν =3-10 11 - 4 . 10 14 Hz, λ =8 . 10 -7 - 2 . 10 -3 m.

Radiated by atoms and molecules of matter.

Infrared radiation is emitted by all bodies at any temperature.

A person emits electromagnetic waves λ≈9. 10 -6 m.

Properties

Passes through some opaque bodies, as well as through rain, haze, snow.
Produces a chemical effect on photographic plates.
Absorbed by the substance, heats it.
Causes an internal photoelectric effect in germanium.
Invisible.

Application. Get images of objects in the dark, night vision devices (night binoculars), fog. They are used in forensic science, in physiotherapy, in industry for drying painted products, building walls, wood, fruits.

Part of electromagnetic radiation perceived by the eye (from red to violet):

Properties.AT affects the eye.

(less than violet light)

Sources: discharge lamps with quartz tubes (quartz lamps).

Radiated by all solids with T > 1000°C, as well as luminous mercury vapor.

Properties. 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.

X-rays

They are emitted during high acceleration of electrons, for example, their deceleration in metals. Obtained using an X-ray tube: electrons in a vacuum tube (p = 10 -3 -10 -5 Pa) are accelerated by an electric field at high voltage, reaching the anode, and are sharply decelerated upon impact. When braking, the electrons move with acceleration and emit electromagnetic waves with a short length (from 100 to 0.01 nm). Properties Interference, X-ray diffraction on the crystal lattice, large penetrating power. Irradiation in high doses causes radiation sickness. Application. In medicine (diagnosis of diseases of internal organs), in industry (control of the internal structure of various products, welds).

γ radiation

Sources: atomic nucleus (nuclear reactions). Properties. It has a huge penetrating power, has a strong biological effect. Application. In medicine, manufacturing γ - flaw detection). Application. In medicine, in industry.

A common property of electromagnetic waves is also that all radiations have 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.

The scale of electromagnetic radiation conditionally includes seven ranges:

1. Low frequency oscillations

2. Radio waves

3. Infrared

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 with the help of rockets, artificial earth satellites and spacecraft. 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. 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.

x-ray radiation

x-ray radiation- electromagnetic waves with a wavelength from 8 * 10-6 cm to 10-10 cm.

There are two types of X-rays: bremsstrahlung and characteristic.

brake arises when fast electrons are slowed down by any obstacle, in particular, by metallic electrons.

The bremsstrahlung of electrons has a continuous spectrum, which differs from the continuous spectra of radiation produced by solids or liquids.

Characteristic X-rays has a line spectrum. Characteristic radiation arises as a result of the fact that an external fast electron decelerating in a substance pulls out an electron located on one of the inner shells from an atom of the substance. In the transition to the vacant place of an electron more distant, an X-ray photon arises.

Device for obtaining x-rays - x-ray tube.

Schematic representation of an x-ray tube.

X - X-rays, K - cathode, A - anode (sometimes called anticathode), C - heat sink, U h- cathode heating voltage, U a- accelerating voltage, W in - water cooling inlet, W out - water cooling outlet.

Cathode 1 is a tungsten spiral that emits electrons due to thermionic emission. Cylinder 3 focuses the flow of electrons, which then collide with the metal electrode (anode) 2. In this case, x-rays appear. The voltage between the anode and cathode reaches several tens of kilovolts. A deep vacuum is created in the tube; the gas pressure in it does not exceed 10 _0 mm Hg. Art.

The electrons emitted by the hot cathode are accelerated (no X-rays are emitted, because the acceleration is too low) and hit the anode, where they are sharply decelerated (X-rays are emitted: the so-called bremsstrahlung)

At the same time, electrons are knocked out of the inner electron shells of the metal atoms from which the anode is made. Empty spaces in the shells are occupied by other electrons of the atom. In this case, X-ray radiation is emitted with a certain energy characteristic of the anode material (characteristic radiation )

X-rays are characterized by a short wavelength, a large "hardness".

Properties:

high penetrating power;

action on photographic plates;

the ability to cause ionization in the substances through which these rays pass.

Application:

X-ray diagnostics. With the help of X-rays, it is possible to "enlighten" the human body, as a result of which it is possible to obtain an image of the bones, and in modern devices, of internal organs.

X-ray therapy

The detection of defects in products (rails, welds, etc.) using X-rays is called X-ray flaw detection.

In materials science, crystallography, chemistry and biochemistry, X-rays are used to elucidate the structure of substances at the atomic level using X-ray diffraction scattering (X-ray diffraction analysis). A famous example is the determination of the structure of DNA.

At airports, X-ray television introscopes are actively used to view the contents of hand luggage and baggage in order to visually detect dangerous objects on the monitor screen.

The purpose of the lesson: to provide during the lesson a repetition of the basic laws, properties of electromagnetic waves;

Educational: Systematize the material on the topic, carry out the correction of knowledge, some of its deepening;

Educational: Development of students' oral speech, students' creative skills, logic, memory; cognitive abilities;

Educational: To form students' interest in the study of physics. educate accuracy and skills for the rational use of one's time;

Lesson type: lesson of repetition and correction of knowledge;

Equipment: computer, projector, presentation "Scale of electromagnetic radiation", disk "Physics. Library of visual aids.

During the classes:

1. Explanation of new material.

1. We know that the length of electromagnetic waves is very different: from values of the order of 1013 m (low-frequency oscillations) to 10 -10 m (g-rays). Light is an insignificant part of the wide 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.
2. It is customary to highlight low frequency radiation, radio radiation, infrared rays, visible light, ultraviolet rays, x-rays andg radiation. With all these radiations except g-radiation, you are already familiar. The shortest g radiation emitted by atomic nuclei.
3. There is no fundamental difference between 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.
4. Radiation of different 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.
5. 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 g radiation that is strongly absorbed by the atmosphere.
6. As the wavelength decreases quantitative differences in wavelengths lead to significant qualitative differences.
7. Radiations of different wavelengths differ greatly from each other in terms of their absorption by matter. Shortwave radiation (X-ray and especially g 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 summarize the knowledge about waves and write down everything in the form of tables.

1. Low frequency oscillations

	*Low frequency vibrations*
Wavelength(m)	10 13 - 10 5
Frequency Hz)	3 10 -3 - 3 10 3
Energy(EV)	1 - 1.24 10 -10
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	Lodge (1893), Tesla (1983)
Application	Cinema, broadcasting (microphones, loudspeakers)

2. Radio waves

	*radio waves*
Wavelength(m)	10 5 - 10 -3
Frequency Hz)	3 10 3 - 3 10 11
Energy(EV)	1.24 10-10 - 1.24 10 -2
Source	Oscillatory circuit Macroscopic vibrators
Receiver	Sparks in the gap of the receiving vibrator The glow of a gas discharge tube, coherer
Discovery history	Feddersen (1862), Hertz (1887), Popov, Lebedev, Rigi
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 10 14
Energy(EV)	1.24 10 -2 - 1.65
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	Rubens and Nichols (1896),
Application	In criminology, 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,

4. Visible radiation

5. Ultraviolet radiation

	*Ultraviolet radiation*
Wavelength(m)	3.8 10 -7 - 3 10 -9
Frequency Hz)	8 10 14 - 10 17
Energy(EV)	3.3 - 247.5 EV
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

6. x-ray radiation

	*x-ray radiation*
Wavelength(m)	10 -9 - 3 10 -12
Frequency Hz)	3 10 17 - 3 10 20
Energy(EV)	247.5 - 1.24 105 EV
Source	Electronic X-ray tube (voltage at the anode - up to 100 kV. pressure in the cylinder - 10 -3 - 10 -5 N / m 2, cathode - incandescent filament. Anode material W, Mo, Cu, Bi, Co, Tl, etc. Η = 1-3%, radiation - high energy quanta) solar corona
Receiver	Camera roll, Glow of some crystals
Discovery history	W. Roentgen, Milliken
Application	Diagnosis and treatment of diseases (in medicine), Defectoscopy (control of internal structures, welds)

7. Gamma radiation

Conclusion
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).

Literature:

"Physics-11" Myakishev
Disk “Lessons of physics of Cyril and Methodius. Grade 11 "()))" Cyril and Methodius, 2006)
Disk "Physics. Library of visual aids. Grades 7-11 "((1C: Bustard and Formosa 2004)
Internet resources

The scale of electromagnetic waves is a continuous sequence of frequencies and lengths of electromagnetic radiation, which is an alternating magnetic field propagating in space. The theory of electromagnetic phenomena by James Maxwell made it possible to establish that in nature there are electromagnetic waves of different lengths.

The wavelength or the frequency of the wave associated with it characterizes not only the wave, but also the quantum properties of the electromagnetic field. Accordingly, in the first case, the electromagnetic wave is described by the classical laws studied in this course.

Consider the concept of the spectrum of electromagnetic waves. The spectrum of electromagnetic waves is the frequency band of electromagnetic waves that exist in nature.

The spectrum of electromagnetic radiation in order of increasing frequency is:

antenna

1) Low frequency waves(λ>);

2) Radio waves();

Atom
3) Infrared(m);

4) Light emission ();

5) X-ray radiation ();

Atomic nuclei

6) Gamma radiation (λ).

Different sections of the electromagnetic spectrum differ in the way they emit and receive waves belonging to one or another section of the spectrum. For this reason, there are no sharp boundaries between different parts of the electromagnetic spectrum, but each range is due to its own characteristics and the prevalence of its own laws, determined by the ratios of linear scales.

Radio waves are studied by classical electrodynamics. Infrared light and ultraviolet radiation are studied both by classical optics and quantum physics. X-ray and gamma radiation is studied in quantum and nuclear physics.

Infrared radiation

Infrared radiation is a part of the solar radiation spectrum, which is directly adjacent to the red part of the visible region of the spectrum and which has the ability to heat most objects. The human eye is unable to see in this part of the spectrum, but we can feel warmth. As you know, any object whose temperature exceeds (-273) degrees Celsius radiates, and the spectrum of its radiation is determined only by its temperature and emissivity. Infrared radiation has two important characteristics: the wavelength (frequency) of radiation and intensity. This part of the electromagnetic spectrum includes radiation with a wavelength from 1 millimeter to eight thousand atomic diameters (about 800 nm).

Infrared rays are absolutely safe for the human body, unlike x-rays, ultraviolet or microwaves. Some animals (for example, burrowing vipers) even have sensory organs that allow them to locate warm-blooded prey by infrared radiation from its body.

Opening

Infrared radiation was discovered in 1800 by the English scientist W. Herschel, who discovered that in the spectrum of the Sun obtained using a prism beyond the red light boundary (i.e., in the invisible part of the spectrum), the temperature of the thermometer rises (Fig. 1). In the 19th century it has been proved that infrared radiation obeys the laws of optics and, therefore, is of the same nature as visible light.

Application

Infra-red rays for the treatment of diseases have been used since ancient times, when doctors used burning coals, hearths, heated iron, sand, salt, clay, etc. to cure frostbite, ulcers, carbuncles, bruises, bruises, etc. Hippocrates described how they were used to treat wounds, ulcers, cold injuries, etc. In 1894, Kellogg introduced electric incandescent lamps into therapy, after which infrared rays were successfully applied in diseases of the lymphatic system, joints, chest (pleurisy), abdominal organs (enteritis, cramps, etc.), liver and gallbladder. bubble.

In the infrared spectrum there is a region with wavelengths from about 7 to 14 microns (the so-called long-wavelength part of the infrared range), which has a truly unique beneficial effect on the human body. This part of the infrared radiation corresponds to the radiation of the human body itself with a maximum at a wavelength of about 10 microns. Therefore, our body perceives any external radiation with such wavelengths as “our own.” The most famous natural source of infrared rays on our Earth is the Sun, and the most famous artificial source of long-wave infrared rays in Russia is a Russian stove, and every person must have tested on their beneficial effects.

Infrared diodes and photodiodes are widely used in remote controls, automation systems, security systems, some mobile phones, etc. Infrared rays do not distract a person's attention due to their invisibility.

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 expended with infrared drying is less than those with traditional methods.

Infrared detectors are widely used by rescue services, for example, to detect living people under rubble after earthquakes or other natural and man-made disasters.

A positive side effect is also the sterilization of food products, an increase in the resistance to corrosion of the surfaces covered with paints.

A feature of the use of infrared radiation in the food industry is the possibility of penetration of an electromagnetic wave into such capillary-porous products as grain, cereals, flour, etc. to a depth of up to 7 mm. This value depends on the nature of the surface, structure, properties of the material and the frequency response of the radiation. An electromagnetic wave of a certain frequency range has not only a thermal, but also a biological effect on the product, it helps to accelerate biochemical transformations in biological polymers (starch, protein, lipids)

Ultra-violet rays

Ultraviolet rays include electromagnetic radiation with a wavelength from several thousand to several atomic diameters (400-10 nm). In this part of the spectrum, radiation begins to affect the vital activity of living organisms. Soft ultraviolet rays in the solar spectrum (with wavelengths approaching the visible part of the spectrum), for example, cause a tan in moderate doses, and severe burns in excess. Hard (short-wavelength) ultraviolet is harmful to biological cells and is therefore used in medicine to sterilize surgical instruments and medical equipment, killing all microorganisms on their surface.

All life on Earth is protected from the harmful effects of hard ultraviolet radiation by the ozone layer of the earth's atmosphere, which absorbs most of the hard ultraviolet rays in the solar radiation spectrum. If not for this natural shield, life on Earth would hardly have come to land from the waters of the oceans. However, despite the protective ozone layer, some of the harsh ultraviolet rays reach the Earth's surface and can cause skin cancer, especially in people who are naturally prone to pallor and do not tan well in the sun.

Discovery history

Shortly after infrared radiation was discovered, the German physicist Johann Wilhelm Ritter began looking for radiation at the opposite end of the spectrum, with a wavelength shorter than that of violet. In 1801, he 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. Then, many scientists, including Ritter, came to the agreement that light consists of three separate components: an oxidizing or thermal (infrared) component, an illuminating component (visible light), and a reducing (ultraviolet) component. At that time, ultraviolet radiation was also called "actinic radiation."

Application

The energy of ultraviolet quanta is sufficient to destroy biological molecules, in particular DNA and proteins. This is one of the methods for the destruction of microbes.

It causes sunburn on the skin and is necessary for the production of vitamin D. But excessive exposure is fraught with the development of skin cancer. UV radiation is harmful to the eyes. Therefore, on the water and especially on the snow in the mountains, it is imperative to wear goggles.

To protect documents from counterfeiting, they are often provided with UV labels that are only visible under UV light conditions. Most passports, as well as banknotes of various countries, contain security elements in the form of paint or threads that glow in ultraviolet light.

Many minerals contain substances that, when illuminated with ultraviolet radiation, begin to emit visible light. Each impurity glows in its own way, which makes it possible to determine the composition of a given mineral by the nature of the glow.

x-ray radiation

X-rays are electromagnetic waves whose photon energy lies on an energy scale between ultraviolet radiation and gamma radiation, which corresponds to wavelengths from to m).

Receipt

X-rays are produced by strong acceleration of charged particles (mainly electrons) or by high-energy transitions in the electron shells of atoms or molecules. Both effects are used in X-ray tubes, in which electrons emitted from a hot cathode are accelerated (no X-rays are emitted, because the acceleration is too low) and hit the anode, where they are sharply decelerated (in this case, X-rays are emitted: i.e. X-rays are emitted). n. bremsstrahlung) and at the same time knock out electrons from the inner electron shells of the atoms of the metal from which the anode is made. Empty spaces in the shells are occupied by other electrons of the atom. In this case, X-ray radiation is emitted with a certain energy characteristic of the anode material ( characteristic radiation)

In the process of acceleration-deceleration, only 1% of the kinetic energy of the electron goes to X-rays, 99% of the energy is converted into heat.

Opening

The discovery of X-rays is attributed to Wilhelm Conrad Roentgen. He was the first to publish an article on X-rays, which he called x-rays (x-ray). Roentgen's article entitled "On a new type of rays" was published on December 28, 1895.

Careful examination showed Roentgen "that the black cardboard, which is not transparent either to the visible and ultraviolet rays of the sun, or to the rays of an electric arc, is permeated with some kind of agent that causes vigorous fluorescence." Roentgen investigated the penetrating power of this "agent", which he called "X-rays" for short, for various substances. He found that the rays pass freely through paper, wood, ebonite, thin layers of metal, but are strongly delayed by lead.

Figure Crookes' experiment with a cathode ray

He then describes the sensational experience: "If you hold your hand between the discharge tube and the screen, you can see the dark shadows of the bones in the faint outline of the shadow of the hand itself." It was the first X-ray examination of the human body. Roentgen also received the first x-rays, attaching them to his brochure. These shots made a huge impression; the discovery had not yet been completed, and X-ray diagnostics had already begun its journey. “My laboratory was flooded with doctors bringing in patients who suspected that they had needles in various parts of the body,” wrote the English physicist Schuster.

Already after the first experiments, Roentgen firmly established that X-rays differ from cathode rays, they do not carry a charge and are not deflected by a magnetic field, but are excited by cathode rays. "... X-rays are not identical with cathode rays, but are excited by them in the glass walls of the discharge tube," wrote Roentgen.

Figure Experience with the first x-ray tube

He also established that they are excited not only in glass, but also in metals.

Mentioning the Hertz-Lenard hypothesis that cathode rays "are a phenomenon occurring in the ether," Roentgen points out that "we can say something similar about our rays." However, he failed to detect the wave properties of the rays, they "behave differently than hitherto known ultraviolet, visible, infrared rays." In their chemical and luminescent actions, according to Roentgen, they are similar to ultraviolet rays. In the first communication, he expressed the suggestion left later that they could be longitudinal waves in the ether.

Application

With the help of X-rays, it is possible to “enlighten” the human body, as a result of which it is possible to obtain an image of the bones, and in modern devices, of the internal organs.

The detection of defects in products (rails, welds, etc.) using X-rays is called X-ray flaw detection.

They are used for technological control of microelectronic products and allow to identify the main types of defects and changes in the design of electronic components.

In materials science, crystallography, chemistry and biochemistry, X-rays are used to elucidate the structure of substances at the atomic level using diffraction X-ray scattering.

X-rays can be used to determine the chemical composition of a substance. At airports, X-ray television introscopes are actively used to view the contents of hand luggage and baggage in order to visually detect dangerous objects on the monitor screen.

X-ray therapy is a section of radiation therapy that covers the theory and practice of therapeutic use. X-ray therapy is carried out mainly with superficially located tumors and with some other diseases, including skin diseases.

Biological impact

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.

Conclusion:

Electromagnetic radiation is a change in the state of an electromagnetic field (perturbation) that can propagate in space.

With the help of quantum electrodynamics, electromagnetic radiation can be considered not only as electromagnetic waves, but also as a stream of photons, that is, particles that are elementary quantum excitation of an electromagnetic field. The waves themselves are characterized by such features as length (or frequency), polarization and amplitude. Moreover, the properties of particles are stronger, the shorter the wavelength. These properties are especially pronounced in the phenomenon of the photoelectric effect (knocking out electrons from the surface of a metal under the action of light), discovered in 1887 by G. Hertz.

Such dualism is confirmed by Planck's formula ε = hν. This formula relates the energy of a photon, which is a quantum characteristic, and the oscillation frequency, which is a wave characteristic.

Depending on the frequency range, several types of electromagnetic radiation are distinguished. Although the boundaries between these types are rather arbitrary, because the speed of propagation of waves in vacuum is the same (equal to 299,792,458 m/s), therefore, the oscillation frequency is inversely proportional to the length of the electromagnetic wave.

Types of electromagnetic radiation differ in the way they are obtained:

Despite the physical differences, in all sources of electromagnetic radiation, whether it be a radioactive substance, an incandescent lamp or a television transmitter, this radiation is excited by electric charges moving with acceleration. There are two main types of sources . In "microscopic" sources charged particles jump from one energy level to another within atoms or molecules. Radiators of this type emit gamma, x-ray, ultraviolet, visible and infrared, and in some cases even longer wavelength radiation (an example of the latter is the line in the hydrogen spectrum corresponding to a wavelength of 21 cm, which plays an important role in radio astronomy). Sources of the second type can be called macroscopic . In them, the free electrons of the conductors perform synchronous periodic oscillations.

There are different registration methods:

Visible light is perceived by the eye. Infrared radiation is predominantly thermal radiation. It is registered by thermal methods, as well as partially by photoelectric and photographic methods. Ultraviolet radiation is chemically and biologically active. It causes the phenomenon of the photoelectric effect, fluorescence and phosphorescence (glow) of a number of substances. It is recorded by photographic and photoelectric methods.

They are also absorbed and reflected differently by the same media:

They have different effects on biological objects at the same radiation intensity:

The effects of different types of radiation on the human body are different: gamma and x-ray radiation penetrate it, causing tissue damage, visible light causes a visual sensation in the eye, infrared radiation, falling on the human body, heats it up, and radio waves and low-frequency electromagnetic oscillations by the human body and are not felt at all. Despite these obvious differences, all these types of radiation are, in essence, different aspects of the same phenomenon.

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 students' oral speech, students' creative skills, 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

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. However, it was during the study of this small part of the spectrum that other radiations with unusual properties were discovered.
It is customary to allocate low frequency radiation, radio radiation, 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, the 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 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.

(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. 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 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.

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 (  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 the body's immune system, 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, traces of restoration that are not visible to the eye can be detected in the paintings). 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 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 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-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.

(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, like light, is not deflected by a 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 types of 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 common 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)

Conclusion:

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

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

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

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

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

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

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

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

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