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

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.

slide 2

Scale of electromagnetic radiation.

The electromagnetic wave scale extends from long radio waves to gamma rays. Electromagnetic waves of various lengths are conditionally divided into ranges according to various criteria (method of production, method of registration, nature of interaction with matter).

slide 3

slide 4

electromagnetic radiation

1. Gamma radiation 2. Infrared 3. X-ray 4. Radio radiation and microwaves 5. Visible range 6. Ultraviolet

slide 5

Gamma radiation

Application

slide 6

Gamma radiation In the field of discovery of gamma rays, one of the first places belongs to the Englishman Ernest Rutherford. Rutherford set himself the goal of not just discovering new radiating substances. He wanted to find out what their rays were. He correctly assumed that charged particles could be encountered in these beams. And they deviate in a magnetic field. In 1898, Rutherford embarked on a study of uranium radiation, the results of which were published in 1899 in the article "The radiation of uranium and the electrical conductivity created by it." Rutherford passed a strong beam of radium beams between the poles of a powerful magnet. And his assumptions came true.

Slide 7

The radiation was recorded by its action on a photographic plate. While there was no magnetic field, one spot appeared on the plate from the rays of radium falling on it. But the beam passed through a magnetic field. Now it kind of fell apart. One beam deviated to the left, the other to the right. The deflection of rays in a magnetic field clearly indicated that the composition of the radiation included charged particles; from this deviation one could also judge the sign of the particles. According to the first two letters of the Greek alphabet, Rutherford named the two components of the radiation of radioactive substances. Alpha rays () - part of the radiation that was deflected, as positive particles would be deflected. Negative particles were designated beta (). And in 1900, another component was discovered in the radiation of uranium by Villars, which did not deviate in a magnetic field and had the greatest penetrating power, it was called gamma rays (). These, as it turned out, were "particles" of electromagnetic radiation - the so-called gamma quanta. Gamma radiation, short-wave electromagnetic radiation. On the scale of electromagnetic waves, it borders on hard X-ray radiation, occupying the entire frequency range > 3 * 1020 Hz, which corresponds to wavelengths 

Slide 8

Gamma radiation occurs during the decay of radioactive nuclei, elementary particles, during the annihilation of particle-antiparticle pairs, as well as during the passage of fast charged particles through matter. Gamma radiation, which accompanies the decay of radioactive nuclei, is emitted during the transition of the nucleus from a more excited energy state to a less excited one or main. The emission of a gamma-quantum by the nucleus does not entail a change in the atomic number or mass number, in contrast to other types of radioactive transformations. The linewidth of gamma radiation is usually extremely small (~10-2 eV). Since the distance between the levels is many times greater than the line width, the gamma-ray spectrum is line-shaped, i.e. consists of a number of discrete lines. The study of the spectra of gamma radiation makes it possible to establish the energies of the excited states of nuclei.

Slide 9

The source of gamma radiation is a change in the energy state of the atomic nucleus, as well as the acceleration of freely charged particles. Gamma quanta with high energies are emitted during the decay of some elementary particles. Thus, the decay of a p° meson at rest gives rise to gamma radiation with an energy of ~70 MeV. gamma radiation from the decay of elementary particles also forms a line spectrum. However, elementary particles undergoing decay often move at speeds comparable to the speed of light. As a result, a Doppler broadening of the line occurs and the spectrum of gamma radiation is smeared over a wide energy range. Gamma radiation, formed during the passage of fast charged particles through matter, is caused by their deceleration in the Coulomb field of the atomic nuclei of matter. Bremsstrahlung gamma radiation, like bremsstrahlung x-rays, is characterized by a continuous spectrum, the upper limit of which coincides with the energy of a charged particle, such as an electron. In interstellar space, gamma radiation can arise as a result of collisions of quanta of softer long-wave electromagnetic radiation, such as light, with electrons accelerated by the magnetic fields of space objects. In this case, a fast electron transfers its energy to electromagnetic radiation and visible light turns into harder gamma radiation. A similar phenomenon can take place under terrestrial conditions when high-energy electrons produced at accelerators collide with visible light photons in intense light beams produced by lasers. The electron transfers energy to a light photon, which turns into a gamma ray. It is possible in practice to convert individual photons of light into high-energy gamma-ray quanta.

Slide 10

Gamma radiation has a high penetrating power, that is, it can penetrate large thicknesses of matter without noticeable attenuation. It passes through a meter-long layer of concrete and a layer of lead several centimeters thick.

slide 11

The main processes that occur during the interaction of gamma radiation with matter are photoelectric absorption (photoelectric effect), Compton scattering (Compton effect) and the formation of electron-positron pairs. With the photoelectric effect, a gamma quantum is absorbed by one of the electrons of the atom, and the energy of the gamma quantum is converted, minus the binding energy of the electron in the atom, into the kinetic energy of the electron flying out of the atom. The probability of the photoelectric effect is directly proportional to the 5th power of the element's atomic number and inversely proportional to the 3rd power of the gamma radiation energy. With the Compton effect, a g-quantum is scattered by one of the electrons weakly bound in the atom. Unlike the photoelectric effect, with the Compton effect, the gamma-quantum does not disappear, but only changes the energy (wavelength) and direction of propagation. As a result of the Compton effect, a narrow beam of gamma rays becomes wider, and the radiation itself becomes softer (long-wavelength). The intensity of Compton scattering is proportional to the number of electrons in 1 cm3 of the substance, and therefore the probability of this process is proportional to the atomic number of the substance. The Compton effect becomes noticeable in substances with a low atomic number and at gamma radiation energies exceeding the binding energy of electrons in atoms. If the energy of a gamma quantum exceeds 1.02 MeV, the process of formation of electron-positron pairs in the electric field of nuclei becomes possible. The probability of pair formation is proportional to the square of the atomic number and increases with increasing hv. Therefore, at hv ~ 10, the main process in any substance is the formation of pairs. The reverse process of annihilation of an electron-positron pair is a source of gamma radiation. Almost all -radiation coming to the Earth from space is absorbed by the Earth's atmosphere. This provides the possibility of the existence of organic life on Earth. -Radiation occurs during the explosion of a nuclear weapon due to the radioactive decay of nuclei.

slide 12

Gamma radiation is used in technology, for example, to detect defects in metal parts - gamma flaw detection. In radiation chemistry, gamma radiation is used to initiate chemical transformations, such as polymerization processes. Gamma radiation is used in the food industry to sterilize food. The main sources of gamma radiation are natural and artificial radioactive isotopes, as well as electron accelerators. The effect of gamma radiation on the body is similar to the effect of other types of ionizing radiation. Gamma radiation can cause radiation damage to the body, up to its death. The nature of the influence of gamma radiation depends on the energy of γ-quanta and spatial features of exposure, for example, external or internal. Gamma radiation is used in medicine for the treatment of tumors, for sterilization of premises, equipment and drugs. Gamma radiation is also used to obtain mutations with subsequent selection of economically useful forms. This is how highly productive varieties of microorganisms (for example, to obtain antibiotics) and plants are bred.

slide 13

infrared range

Origin And Terrestrial Application

Slide 14

William Herschel first noticed that beyond the red edge of the Sun's spectrum obtained with a prism, there is invisible radiation that causes the thermometer to heat up. This radiation was later called thermal or infrared.

Near infrared radiation is very similar to visible light and is detected by the same instruments. In the middle and far IR, bolometers are used to indicate changes. In the mid-IR range, the entire planet Earth and all objects on it, even ice, shine. Due to this, the Earth is not overheated by solar heat. But not all infrared radiation passes through the atmosphere. There are only a few windows of transparency, the rest of the radiation is absorbed by carbon dioxide, water vapor, methane, ozone and other greenhouse gases that prevent the Earth from cooling rapidly. Due to absorption in the atmosphere and thermal radiation of objects, mid- and far-infrared telescopes are taken out into space and cooled to the temperature of liquid nitrogen or even helium.

slide 15

Sources In the infrared, the Hubble telescope can see more galaxies than stars.

A fragment of one of the so-called Hubble Deep Fields. In 1995, a space telescope accumulated light coming from one part of the sky for 10 days. This made it possible to see extremely faint galaxies, the distance to which is up to 13 billion light years (less than one billion years from the Big Bang). Visible light from such distant objects experiences a significant redshift and becomes infrared. The observations were carried out in a region far from the plane of the galaxy, where relatively few stars are visible. Therefore, most of the registered objects are galaxies at different stages of evolution.

slide 16

The Sombrero Galaxy in infrared

The giant spiral galaxy, also referred to as M104, is located in the cluster of galaxies in the constellation Virgo and is visible to us almost edge-on. It has a huge central bulge (a spherical thickening in the center of the galaxy) and contains about 800 billion stars - 2-3 times more than the Milky Way. At the center of the galaxy is a supermassive black hole with a mass of about a billion solar masses. This is determined from the velocities of the stars near the center of the galaxy. In the infrared, a ring of gas and dust is clearly visible in the galaxy, in which stars are actively born.

Slide 17

Nebulae and dust clouds near the center of the Galaxy in the infrared

Slide 18

ReceiversSpitzer Infrared Space Telescope

The main mirror, 85 cm in diameter, is made of beryllium and cooled to a temperature of 5.5 K to reduce the mirror's own infrared radiation. The telescope was launched in August 2003 under the NASA Four Great Observatory Program, which includes: the Compton Gamma Observatory (1991–2000, 20 keV-30 GeV), see the sky in 100 MeV gamma rays, the Chandra X-ray Observatory » (1999, 100 eV-10 keV), Hubble Space Telescope (1990, 100–2100 nm), Spitzer Infrared Telescope (2003, 3–180 µm). It is expected that the lifetime of the Spitzer telescope will be about 5 years. The telescope got its name in honor of the astrophysicist Lyman Spitzer (1914–97), who in 1946, long before the launch of the first satellite, published the article “Advantages for Astronomy of an Extraterrestrial Observatory”, and 30 years later convinced NASA and the US Congress to start developing a space telescope “ Hubble.

Slide 19

Ground application:Night vision device

The device is based on an electron-optical converter (IOC), which makes it possible to significantly (from 100 to 50 thousand times) amplify weak visible or infrared light. The lens creates an image on the photocathode, from which, as in the case of a PMT, electrons are knocked out. Then they are accelerated by a high voltage (10–20 kV), focused by electron optics (an electromagnetic field of a specially selected configuration), and fall onto a fluorescent screen similar to a television one. On it, the image is viewed through the eyepieces. The acceleration of photoelectrons makes it possible in low light conditions to use literally every quantum of light to obtain an image, however, in complete darkness, illumination is required. In order not to give out the presence of an observer, a near-IR spotlight (760–3000 nm) is used for this.

Slide 20

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

slide 21

Radiator

All the energy consumed by an electric heater is ultimately converted into heat. A significant part of the heat is carried away by the air that comes into contact with the hot surface, expands and rises, so that the ceiling is mainly heated. To avoid this, heaters are equipped with fans that direct warm air, for example, to a person’s legs and help to mix the air in the room. But there is another way to transfer heat to surrounding objects: the infrared radiation of the heater. It is the stronger, the hotter the surface and the larger its area. To increase the area, radiators are made flat. However, the surface temperature cannot be high. In other models of heaters, a spiral heated to several hundred degrees (red heat) and a concave metal reflector are used, which creates a directed stream of infrared radiation.

slide 22

x-ray

1. Sources, Application

slide 23

2. Highlighting a new type of study, Wilhelm Roentgen called it X-rays (X-rays). Under this name, it is known all over the world, except for Russia. The most characteristic source of X-rays in space is the hot inner regions of accretion disks around neutron stars and black holes. Also in the X-ray range, the solar corona shines, heated to 1–2 million degrees, although there are only about 6 thousand degrees on the surface of the Sun. But x-rays can be obtained without extreme temperatures. In the radiating tube of a medical X-ray machine, electrons are accelerated by a voltage of several kilovolts and crash into a metal screen, emitting X-rays during braking. Body tissues absorb x-rays in different ways, this allows you to study the structure of internal organs. X-rays do not penetrate through the atmosphere; cosmic X-ray sources are observed only from orbit. Hard x-rays are recorded by scintillation sensors. When X-ray quanta are absorbed, a glow appears in them for a short time, which is captured by photomultipliers. Soft X-rays are focused by oblique-incidence metal mirrors, from which the rays are reflected at an angle of less than one degree, like pebbles from the surface of water.

slide 24

SourcesX-ray sources near the center of our Galaxy

A fragment of an image of the vicinity of the center of the Galaxy, obtained by the X-ray telescope "Chandra". A number of bright sources are visible, which, most likely, are accretion disks around compact objects - neutron stars and black holes.

Slide 25

Surroundings of a pulsar in the Crab Nebula

The Crab Nebula is the remnant of a supernova that occurred in 1054. The nebula itself is a shell of a star scattered in space, and its core compressed and formed a superdense rotating neutron star with a diameter of about 20 km. The rotation of this neutron star is tracked by strictly periodic oscillations of its radiation in the radio range. But the pulsar also emits in the visible and X-ray ranges. In x-rays, the Chandra telescope was able to image an accretion disk around a pulsar and small jets perpendicular to its plane (cf. an accretion disk around a supermassive black hole).

slide 26

Solar prominences in X-ray

The visible surface of the Sun is heated to about 6 thousand degrees, which corresponds to the visible range of radiation. However, the corona surrounding the Sun is heated to a temperature of more than a million degrees and therefore glows in the X-ray range of the spectrum. This picture was taken during the maximum solar activity, which varies with a period of 11 years. The very surface of the Sun in X-rays practically does not radiate and therefore looks black. During solar minimum, the X-ray emission from the Sun is significantly reduced. The image was taken by the Japanese Yohkoh (“Sunbeam”) satellite, also known as Solar-A, which operated from 1991 to 2001.

Slide 27

ReceiversX-ray telescope "Chandra"

One of the four "Great Observatories" of NASA, named after the American astrophysicist of Indian origin Subramanyan Chandrasekhar (1910–95), Nobel Prize winner (1983), a specialist in the theory of the structure and evolution of stars. The observatory's main instrument is an oblique-incidence X-ray telescope with a diameter of 1.2 m, containing four nested oblique-incidence parabolic mirrors (see the diagram) that turn into hyperbolic ones. The observatory was put into orbit in 1999 and operates in the soft X-ray range (100 eV-10 keV). Chandra's many discoveries include the first image of an accretion disk around a pulsar in the Crab Nebula.

Slide 28

Earth application

An electronic lamp that serves as a source of soft x-rays. A voltage of 10–100 kV is applied between two electrodes inside a sealed vacuum flask. Under the action of this voltage, the electrons are accelerated to an energy of 10–100 keV. At the end of the journey, they collide with a polished metal surface and brake sharply, giving off a significant part of the energy in the form of radiation in the X-ray and ultraviolet range.

Slide 29

X-ray

The image is obtained due to the unequal permeability of the tissues of the human body for x-rays. In a conventional camera, the lens refracts the light reflected by the object and focuses it on the film where the image is formed. However, X-rays are very difficult to focus. Therefore, the work of the X-ray machine is more like a contact print of a picture, when the negative is placed on photographic paper and illuminated for a short time. Only in this case, the human body acts as a negative, a special photographic film sensitive to X-rays acts as photographic paper, and an X-ray tube is taken instead of a light source.

slide 30

Radio emission and microwaves

Application

Slide 31

The range of radio emission is opposite to gamma radiation and is also unlimited on the one hand - from long waves and low frequencies. Engineers divide it into many sections. The shortest radio waves are used for wireless data transmission (Internet, cellular and satellite telephony); meter, decimeter and ultrashort waves (VHF) occupy local television and radio stations; short waves (HF) are used for global radio communication - they are reflected from the ionosphere and can go around the Earth; medium and long waves are used for regional broadcasting. Very long waves (VLF) - from 1 km to thousands of kilometers - penetrate salt water and are used to communicate with submarines, as well as to search for minerals. The energy of radio waves is extremely low, but they excite weak oscillations of electrons in a metal antenna. These oscillations are then amplified and recorded. The atmosphere transmits radio waves from 1 mm to 30 m long. They allow observing the nuclei of galaxies, neutron stars, and other planetary systems, but the most impressive achievement of radio astronomy is record-breaking detailed images of cosmic sources, the resolution of which exceeds ten thousandths of an arc second.

slide 32

Microwave

Microwaves are a subrange of radio emission adjacent to infrared. It is also called microwave radiation because it has the highest frequency in the radio band. The microwave range is of interest to astronomers, since it records the relic radiation left over from the time of the Big Bang (another name is the microwave cosmic background). It was emitted 13.7 billion years ago, when the hot matter of the Universe became transparent to its own thermal radiation. As the Universe expanded, the CMB has cooled down and today its temperature is 2.7 K. CMB comes to Earth from all directions. Today, astrophysicists are interested in the inhomogeneities of the sky glow in the microwave range. They are used to determine how galaxy clusters began to form in the early universe in order to test the correctness of cosmological theories. And on Earth, microwaves are used for mundane tasks like heating breakfast and talking on a cell phone. The atmosphere is transparent to microwaves. They can be used to communicate with satellites. There are also projects to transfer energy over a distance using microwave beams.

Slide 33

Sources of the Crab Nebula in the radio range

This image, which was built from observations by the American National Radio Astronomy Observatory (NRAO), can be used to judge the nature of the magnetic fields in the Crab Nebula. The Crab Nebula is the most studied remnant of a supernova explosion. This image shows how it looks in the radio range. Radio emission is generated by fast electrons moving in a magnetic field. The field causes the electrons to turn, that is, to move at an accelerated rate, and when accelerated, the charges emit electromagnetic waves.

slide 34

Computer model of matter distribution in the Universe

Initially, the distribution of matter in the universe was almost perfectly uniform. But still, small (perhaps even quantum) density fluctuations over many millions and billions of years led to the fact that the substance was fragmented. Similar results are obtained from observational surveys of the distribution of galaxies in space. For hundreds of thousands of galaxies, coordinates in the sky and redshifts are determined, by which distances to galaxies are calculated. The figure shows the result of computer simulation of the evolution of the Universe. The motion of 10 billion particles under the action of mutual gravity over 15 billion years was calculated. As a result, a porous structure was formed, vaguely resembling a sponge. Clusters-galaxies are concentrated in its nodes and edges, and between them there are vast deserts, where there are almost no objects - astronomers call them voids (from the English void - emptiness).

Slide 35

However, it is possible to achieve good agreement between calculations and observations only if we assume that the visible (luminous in the electromagnetic spectrum) matter is only about 5% of the entire mass of the Universe. The rest falls on the so-called dark matter and dark energy, which manifest themselves only by their gravity and whose nature has not yet been established. Their study is one of the most urgent problems of modern astrophysics.

slide 36

Quasar: active galactic nucleus

In the radio image of the quasar, regions of high intensity of radio emission are shown in red: in the center is the active nucleus of the galaxy, and on the sides of it are two jets. The galaxy itself practically does not radiate in the radio range. When too much material is accreted onto the supermassive black hole at the center of a galaxy, a huge amount of energy is released. This energy accelerates part of the matter to near-light speeds and ejects it with relativistic plasma jets in two opposite directions perpendicular to the axis of the accretion disk. When these jets collide with the intergalactic medium and slow down, the particles entering them emit radio waves.

Slide 37

Radio galaxy: map of isolines of radio brightness

Contour maps are usually used to represent images taken at a single wavelength, which is especially true for the radio band. By the principle of construction, they are similar to contour lines on a topographic map, but instead of points with a fixed height above the horizon, they connect points with the same radio brightness of the source in the sky. To image space objects in radiation ranges other than the visible one, various techniques are used. Most often these are artificial colors and contour maps. Artificial colors can be used to show what an object would look like if the light-sensitive receptors of the human eye were sensitive not to certain colors in the visible range, but to other frequencies of the electromagnetic spectrum.

Slide 38

ReceiversMicrowave Orbital Probe WMAP

The study of the microwave background was started by ground-based radio telescopes, continued by the Soviet Relikt-1 instrument aboard the Prognoz-9 satellite in 1983 and by the American satellite COBE (Cosmic Background Explorer) in 1989, but the most detailed map of the distribution of the microwave background by the celestial sphere was built in 2003 by the WMAP probe (Wilkinson Microwave Anisotropy Probe). The data obtained impose significant restrictions on the models of galaxy formation and the evolution of the Universe. The cosmic microwave background, also called the CMB, creates radio noise that is almost the same in all directions in the sky. And yet there are very small variations in intensity - about a thousandth of a percent. These are traces of density inhomogeneities in the young Universe, which served as seeds for future clusters of galaxies.

Slide 39

sky surveys

The energy of an unexcited hydrogen atom depends on the mutual orientation of the proton and electron spins. If they are parallel, the energy is slightly higher. Such atoms can spontaneously transition to a state with antiparallel spins, emitting a radio emission quantum that carries away a tiny excess of energy. With a single atom, this happens on average once every 11 million years. But the huge distribution of hydrogen in the universe makes it possible to observe gas clouds at this frequency. The famous 21.1 cm spectral line is another way to observe neutral atomic hydrogen in space. The line arises due to the so-called hyperfine splitting of the ground energy level of the hydrogen atom.

Slide 40

Radio sky on a wave of 73.5 cm, 408 MHz (Bonn)

One of the world's largest full-rotation radio telescopes, the 100-meter Bonn radio telescope, was used to build the survey. This is the longest wavelength of all sky surveys. It was carried out on a wavelength at which a significant number of sources are observed in the Galaxy. In addition, the choice of wavelength was determined by technical reasons.

Slide 41

Earth application

Microwave oven This is how microwave (MW) drying of food, defrosting, cooking and heating takes place. Also, alternating electric currents excite high-frequency currents. These currents can arise in substances where mobile charged particles are present. But sharp and thin metal objects should not be placed in a microwave oven (this is especially true for dishes with sprayed metal decorations for silver and gold). Even a thin ring of gilding along the edge of the plate can cause a powerful electrical discharge that will damage the device that creates an electromagnetic wave in the furnace (magnetron, klystron). The main advantage of the microwave oven is that over time, the products are heated throughout the entire volume, and not just from the surface. Microwave radiation, having a longer wavelength, penetrates deeper than infrared under the surface of products. Inside the food, electromagnetic vibrations excite the rotational levels of water molecules, the movement of which basically causes the food to heat up.

Slide 42

Cellular telephone

In the GSM standard, one base station can provide no more than 8 telephone conversations at the same time. At mass events and during natural disasters, the number of callers increases dramatically, which overloads the base stations and leads to interruptions in cellular communications. For such cases, cellular operators have mobile base stations that can be quickly delivered to a crowded area. A lot of controversy raises the question of the possible harm of microwave radiation from cell phones. During a conversation, the transmitter is in close proximity to the person's head. Repeatedly conducted studies have not yet been able to reliably register the negative effects of radio emission from cell phones on health. Although it is impossible to completely exclude the effect of weak microwave radiation on body tissues, there are no grounds for serious concern. The principle of operation of cellular telephony is based on the use of a radio channel (in the microwave range) for communication between the subscriber and one of the base stations. Information is transmitted between base stations, as a rule, via digital cable networks. The range of the base station - cell size - from several tens to several thousand meters. It depends on the landscape and on the signal strength, which is selected so that there are not too many active subscribers in one cell.

slide 43

TV set

The transmitter of a television station constantly broadcasts a radio signal of a strictly fixed frequency, it is called the carrier frequency. The receiving circuit of the TV is adjusted to it - a resonance occurs in it at the desired frequency, which makes it possible to capture weak electromagnetic oscillations. Information about the image is transmitted by the amplitude of oscillations: large amplitude - high brightness, low amplitude - a dark area of ​​the image. This principle is called amplitude modulation. Radio stations (except FM stations) transmit sound in the same way. With the transition to digital television, the image coding rules change, but the very principle of the carrier frequency and its modulation is preserved. The television image is transmitted on meter and decimeter waves. Each frame is divided into lines, along which the brightness changes in a certain way.

Slide 44

satellite dish

Parabolic antenna for receiving a signal from a geostationary satellite in the microwave and VHF bands. The principle of operation is the same as that of a radio telescope, but the dish does not need to be made movable. At the time of installation, it is sent to the satellite, which always remains in the same place relative to earthly structures. This is achieved by placing the satellite into a geostationary orbit at a height of about 36,000 km above the Earth's equator. The period of revolution along this orbit is exactly equal to the period of rotation of the Earth around its axis relative to the stars - 23 hours 56 minutes 4 seconds. The size of the dish depends on the power of the satellite transmitter and its radiation pattern. Each satellite has a main service area, where its signals are received by a dish with a diameter of 50–100 cm, and a peripheral zone, where the signal weakens rapidly and an antenna up to 2–3 m may be required to receive it.

Slide 45

Visible Range

Earth application

Slide 46

The range of visible light is the narrowest in the entire spectrum. The wavelength in it changes less than twice. Visible light accounts for the maximum radiation in the spectrum of the Sun. Our eyes in the course of evolution have adapted to its light and are able to perceive radiation only in this narrow part of the spectrum. Almost all astronomical observations until the middle of the 20th century were carried out in visible light. The main source of visible light in space is the stars, the surface of which is heated to several thousand degrees and therefore emits light. On Earth, non-thermal light sources are also used, such as fluorescent lamps and semiconductor light-emitting diodes. Mirrors and lenses are used to collect light from weak cosmic sources. Visible light receivers are the retina, photographic film, semiconductor crystals (CCD arrays) used in digital cameras, photocells and photomultipliers. The principle of operation of receivers is based on the fact that the energy of a quantum of visible light is sufficient to provoke a chemical reaction in a specially selected substance or to knock out a free electron from a substance. Then, the amount of light received is determined by the concentration of the reaction products or by the magnitude of the released charge.

Slide 47

Sources

One of the brightest comets of the late 20th century. It was discovered in 1995, when it was still beyond the orbit of Jupiter. This is a record distance for detecting a new comet. It passed perihelion on April 1, 1997, and at the end of May it reached its maximum brightness - about zero magnitude. Comet Hale-Bopp In total, the comet remained visible to the naked eye for 18.5 months - twice the previous record set by the great comet of 1811. The image shows two tails of the comet - dusty and gaseous. The pressure of solar radiation directs them away from the Sun.

Slide 48

Planet Saturn

The second largest planet in the solar system. Belongs to the class of gas giants. The picture was taken by the Cassini interplanetary station, which has been conducting research in the Saturn system since 2004. At the end of the 20th century, ring systems were found in all giant planets - from Jupiter to Neptune, but only in Saturn they are easily accessible even with a small amateur telescope.

Slide 49

sunspots

They live from several hours to several months. The number of spots serves as an indicator of solar activity. By observing the spots for several days, it is easy to notice the rotation of the Sun. The picture was taken with an amateur telescope. Regions of low temperature on the visible surface of the Sun. Their temperature is 4300-4800 K - about one and a half thousand degrees lower than on the rest of the surface of the Sun. Because of this, their brightness is 2–4 times lower, which in contrast creates the impression of black spots. Sunspots occur when the magnetic field slows down convection and thus the removal of heat in the upper layers of the Sun's matter.

Slide 50

Receivers

Amateur telescope In the modern world, amateur astronomy has become a fascinating and prestigious hobby. The simplest instruments with a lens diameter of 50–70 mm, the largest with a diameter of 350–400 mm, are comparable in cost to a prestigious car and require a permanent installation on a concrete foundation under a dome. In skillful hands, such tools may well contribute to great science.

Slide 51

incandescent lamp

It emits visible light and infrared radiation by heating a tungsten coil placed in a vacuum with an electric current. The emission spectrum is very close to black-body with a temperature of about 2000 K. At this temperature, the emission peaks in the near infrared region and is therefore wasted uselessly for lighting purposes. It is not possible to significantly raise the temperature, since in this case the spiral quickly fails. Therefore, incandescent lamps are an uneconomical lighting device. Fluorescent lamps are much more efficient at converting electricity into light.

Slide 52

Ultraviolet

Earth application

Slide 53

The ultraviolet range of electromagnetic radiation lies beyond the violet (shortwave) edge of the visible spectrum. The near ultraviolet from the Sun passes through the atmosphere. 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. Harder UV radiation is absorbed in the atmosphere by molecules of ozone and other gases. It can only be observed from space, which is why it is called vacuum ultraviolet. 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 is believed that as long as there was no ozone in the Earth's atmosphere, which absorbs a significant part of ultraviolet radiation, life could not leave the water on land. Ultraviolet is emitted by objects with temperatures ranging from thousands to hundreds of thousands of degrees, such as young, hot, massive stars. However, UV radiation is absorbed by interstellar gas and dust, so we often see not the sources themselves, but the cosmic clouds illuminated by them. To collect UV radiation, mirror telescopes are used, and photomultipliers are used for registration, and in the near UV, as in visible light, CCD matrices are used.

Slide 54

Sources

The glow is produced when charged particles in the solar wind collide with molecules in Jupiter's atmosphere. Most of the particles under the influence of the planet's magnetic field enter the atmosphere near its magnetic poles. Therefore, radiance occurs in a relatively small area. Similar processes are taking place on Earth and on other planets with an atmosphere and a magnetic field. The image was taken by the Hubble Space Telescope. Aurora on Jupiter in ultraviolet

Slide 55

sky surveys

Sky in Hard Ultraviolet (EUVE) The survey was created by the orbital ultraviolet observatory Extreme Ultraviolet Explorer. The line structure of the image corresponds to the orbital movement of the satellite, and the inhomogeneity of the brightness of individual bands is associated with changes in the calibration of the equipment. Black stripes are areas of the sky that could not be observed. The small number of details in this review is due to the fact that there are relatively few sources of hard ultraviolet and, in addition, ultraviolet radiation is scattered by cosmic dust.

Slide 56

Earth application

Solarium Installation for dosed irradiation of the body with near ultraviolet for tanning. Ultraviolet radiation leads to the release of melanin pigment in the cells, which changes skin color.

Slide 57

Currency detector

Ultraviolet radiation is used to determine the authenticity of banknotes. Polymer fibers with a special dye are pressed into banknotes, which absorbs ultraviolet quanta, and then emits less energetic visible radiation. Under the influence of ultraviolet light, the fibers begin to glow, which is one of the signs of authenticity. The ultraviolet radiation of the detector is invisible to the eye, the blue glow that is noticeable during the operation of most detectors is due to the fact that the ultraviolet sources used also emit in the visible range.

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The source of electromagnetic radiation is always matter. But different levels of organization of matter in matter have a different mechanism for excitation of electromagnetic waves.

So electromagnetic waves have as their source currents flowing in conductors, electrical alternating voltages on metal surfaces (antennas), etc. Infrared radiation has heated objects as its source and is generated by vibrations of body molecules. Optical radiation occurs as a result of the transition of electrons of atoms from one excited orbits to others (stationary ones). X-rays are based on the excitation of the electron shells of atoms by external influences, for example, bombardment by electron beams. Gamma radiation has a source of excited nuclei of atoms, the excitation can be natural, or it can be the result of induced radioactivity.

Electromagnetic wave scale:

Electromagnetic waves are otherwise known as radio waves. Radio waves are divided into subbands (see table).

Subrange name	Wavelength, m	Oscillation frequency, Hz.
Ultra long waves	over 10 4	less than 3 10 4
long waves		310 4 -310 5
medium waves		310 5 -310 6
short waves		310 6 -310 7
Meter waves		310 7 -310 8
decimeter waves		310 8 -310 9
centimeter waves		310 9 -310 10
millimeter waves		310 10 -310 11
submillimeter waves	10 -3 -510 -5	310 11 -310 12

Long and medium waves bend around the surface, are good for short-range and long-range radio communications, but have low capacity;

short waves - reflected from the surface and have a larger capacity, are used for long-distance radio communications;

VHF - distributed only in the line of sight, used for radio communications and television;

IKI - are used for all kinds of thermal devices;

visible light - used in all optical instruments;

UVI - used in medicine;

X-ray radiation is used in medicine and in devices for quality control of products;

gamma rays - vibrations of the surface of the nucleons that make up the nucleus. used in paramagnetic resonance to determine the composition and structure of matter.

2. Changing fields when moving objects. Doppler effect and its application in technology

When an object moves in any force field - electric, magnetic or electromagnetic, its perception of the actions of this field changes. This is due to the fact that the interaction of the object and the field depends on the relative velocity of the matter of the field and the object, and therefore does not remain a constant value. This is most clearly manifested in the so-called Doppler effect.

The Doppler effect is a change in the frequency of oscillations and the wavelength perceived by the receiver of oscillations due to the movement of the wave source and the observer relative to each other. The main reason for the effect is a change in the number of waves that fit in the propagation path between the source and the receiver.

The Doppler effect for sound waves is observed directly. It manifests itself in an increase in the tone (frequency) of the sound when the source of the sound and the observer approach and, accordingly, in a decrease in the tone of the sound when they move away.

The Doppler effect has found application for determining the speed of objects - when determining the speed of a moving car, when measuring the speed of aircraft, when measuring the speed of approach or removal of aircraft from each other.

In the first case, the traffic controller directs the beam of a portable radar towards the car, and determines its speed by the frequency difference between the sent and reflected beam.

In the second case, the Doppler velocity component meter itself is installed directly on the aircraft. Three or four beams are emitted obliquely downwards - to the left forward, to the right forward, to the left back and to the right back. the received signal frequencies are compared with the frequencies of the emitted signals, the frequency differences give an idea of ​​the component of the aircraft movement in the direction of the beam, and then, by recalculating the information received, taking into account the position of the beams relative to the aircraft, the speed and drift angle of the aircraft are calculated.

In the third case, the radar installed on the aircraft determines not only the range to another aircraft, as in conventional radars, but also the Doppler frequency shift, which makes it possible not only to know the distance to another aircraft (target), but also its speed. Against the background, this method allows you to distinguish a moving target from a stationary one.

The use of the Doppler effect together with spectrometers in astronomy makes it possible to obtain a large amount of information about the behavior of stellar objects and formations far from us.

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

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

Register by thermal methods, photoelectric and photographic.

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.