SCALE OF ELECTROMAGNETIC RADIATIONS

We know that the length electromagnetic waves can be very different: from values ​​​​of the order of 103 m (radio waves) to 10-8 cm (x-rays). Light makes up a tiny part of the broad spectrum of electromagnetic waves. Nevertheless, it was during the study of this small part of the spectrum that other radiations with unusual properties were discovered.

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

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

All of the listed types of electromagnetic radiation are also generated by space objects and are successfully studied using rockets, artificial satellites Earth and spaceships. This primarily applies to X-ray and gamma radiation, which are 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 their absorption by matter. Short-wave radiation (X-rays and especially g-rays) are weakly absorbed. Substances that are opaque to optical waves are transparent to these radiations. The reflection coefficient of electromagnetic waves also depends on the wavelength. But the main difference between long-wave and short-wave radiation is that short-wave radiation reveals the properties of particles.

Radio waves

n= 105-1011 Hz, l»10-3-103 m.

Obtained using oscillatory circuits and macroscopic vibrators.

Properties: Radio waves of different frequencies and with different wavelengths are absorbed and reflected differently by media, and exhibit diffraction and interference properties.

Application: Radio communications, television, radar.

Infrared radiation (thermal)

n=3*1011-4*1014 Hz, l=8*10-7-2*10-3 m.

Emitted by atoms and molecules of matter. Infrared radiation is emitted by all bodies at any temperature. A person emits electromagnetic waves l»9*10-6 m.

Properties:

1. Passes through some opaque bodies, also through rain, haze, snow.

2. Produces a chemical effect on photographic plates.

3. Absorbed by a substance, it heats it.

4. Causes an internal photoelectric effect in germanium.

5. Invisible.

6. Capable of interference and diffraction phenomena.

Recorded by thermal, photoelectric and photographic methods.

Application: Obtain images of objects in the dark, night vision devices (night binoculars), and fog. Used in forensics, physiotherapy, and in industry for drying painted products, building walls, wood, and fruit.

Visible radiation

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

n=4*1014-8*1014 Hz, l=8*10-7-4*10-7 m.

Properties: Reflects, refracts, affects the eye, is capable of the phenomena of dispersion, interference, diffraction.

Ultraviolet radiation

n=8*1014-3*1015 Hz, l=10-8-4*10-7 m (less than violet light).

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

Emitted 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 ability, kills microorganisms, in small doses has a beneficial effect on the human body (tanning), but in large doses has a negative biological effect: changes in cell development and metabolism, effects on the eyes.

Application: In medicine, in industry.

X-rays

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, electrons move with acceleration and emit electromagnetic waves with a short length (from 100 to 0.01 nm).

Properties: Interference, X-ray diffraction on a crystal lattice, high penetrating power. Irradiation in large doses causes radiation sickness.

Application: In medicine (diagnosis of diseases internal organs), in industry (control of the internal structure of various products, welds).

g -Radiation

n=3*1020 Hz and more, l=3.3*10-11 m.

Sources: atomic nucleus (nuclear reactions).

Properties: Has enormous penetrating power and has a strong biological effect.

Application: In medicine, manufacturing (g-flaw detection).

Conclusion

The entire scale of electromagnetic waves is evidence that all radiations have both quantum and wave properties. Quantum and wave properties in this case do not exclude, but complement each other. Wave properties appear more clearly at low frequencies and less clearly at high frequencies. Conversely, quantum properties appear more clearly at high frequencies and less clearly at low frequencies. The shorter the wavelength, the brighter the quantum properties appear, and the longer the wavelength, the brighter the wave properties appear. All this serves as confirmation of the law of dialectics (the transition of quantitative changes into qualitative ones).

Lesson objectives:

Lesson type:

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 developed

teacher of the LPR State Institution “LOUSOSH No. 18”

Karaseva I.D.

Lesson objectives: consider the scale of electromagnetic waves, characterize waves of different frequency ranges; show the role of various types of radiation in human life, the influence of various types of radiation on humans; systematize material on the topic and deepen students’ knowledge about electromagnetic waves; develop students’ oral speech, students’ creative skills, logic, memory; cognitive abilities; to develop students’ interest in studying physics; cultivate accuracy and hard work.

Lesson type: lesson in the formation of new knowledge.

Form: lecture with presentation

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

Electromagnetic wave scale"

During the classes

Organizing time.

Motivation for educational and cognitive activities.

The Universe is an ocean of electromagnetic radiation. People live in it, for the most part, without noticing the waves permeating the surrounding space. While warming up by the fireplace or lighting a candle, a person makes the source of these waves work, without thinking about their properties. But knowledge is power: having discovered the nature of electromagnetic radiation, humanity during the 20th century has mastered and put into its service its most diverse types.

Setting the topic and goals of the lesson.

Today we will take a journey along the scale of electromagnetic waves, consider the types of electromagnetic radiation in different frequency ranges. Write down the topic of the lesson: “Types of radiation. Electromagnetic wave scale" (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 it discovered by?

5. Source

6. Receiver (indicator)

7. Application

8. Effect on humans

As you study the topic, you must complete the following table:

Table "Electromagnetic radiation scale"

Presentation of new material.

(Slide 3)

The length of electromagnetic waves can be very different: from values ​​of the order of 10 13 m (low frequency vibrations) up to 10 -10 m ( -rays). Light makes up a tiny part of the broad spectrum of electromagnetic waves. However, it was during the study of this small part of the spectrum that other radiations with unusual properties were discovered.
It is customary to highlight low frequency radiation, radio radiation, infrared rays, visible light, ultraviolet rays, x-rays and -radiation. The shortest wavelength -radiation emits atomic nuclei.

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

(Slide 4)

Radiation of different wavelengths differ from each other in the way they are receiving(antenna radiation, thermal radiation, radiation during braking of fast electrons, etc.) and registration methods.

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

Quantitative differences in wavelengths lead to significant qualitative differences.

Radiations of different wavelengths differ greatly from each other in their absorption by matter. Short-wave radiation (X-rays and especially -rays) are weakly absorbed. Substances that are opaque to optical waves are transparent to these radiations. The reflection coefficient of electromagnetic waves also depends on the wavelength. But the main difference between long-wave and short-wave radiation is that short-wave 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. Radiation of such relatively low frequencies can be neglected. The source of low-frequency radiation is generators alternating current. 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. Source 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 a Hertz vibrator and an oscillatory circuit.

High frequency radio waves, compared to low-frequency radiation leads to noticeable emission of radio waves into space. This allows them to be used to transmit information over various distances. Speech, music (broadcasting), telegraph signals (radio communications), and images of various objects (radiolocation) 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 based on 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. While studying the temperature rise of a thermometer heated by visible light, Herschel discovered the greatest heating of the thermometer outside the region of visible light (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. On infrared radiation accounts for a significant share (from 70 to 80%) of the radiation energy of incandescent lamps with tungsten filament. Infrared radiation emits 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 photos and thermistors, special photo emulsions. Infrared radiation is used to dry wood, food products and various paint coatings(infrared heating), for signaling in case of poor visibility, makes it possible to use optical instruments, allowing you to see in the dark, as well as remote control. Infrared rays are used to guide projectiles and missiles to targets and to detect camouflaged enemies. These rays make it possible to determine the difference in temperatures of individual areas of the surface of the planets, and the structural features of the molecules of matter (spectral analysis). Infrared photography used in biology when studying plant diseases, in medicine when diagnosing skin and vascular diseases, in forensics when detecting counterfeits. Causes fever when exposed to humans 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 ( = 3.85 10 14 - 8 10 14 Hz). The source of visible radiation is valence electrons in atoms and molecules, changing their position in space, as well as free charges, moving quickly. This part of the spectrum gives a person maximum information about the world around him. According to their own physical properties it is similar to other ranges of the spectrum, being only a small part of the spectrum of electromagnetic waves. Radiation having different wavelengths (frequencies) in the visible range has different physiological effects on the retina of the human eye, causing the 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, we can name seven primary colors distinguished by the human eye in the visible range (in order of increasing frequency of radiation): red, orange, yellow, green, blue, indigo, violet. Memorizing 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 occurrence of chemical reactions in plants (photosynthesis) and in animals and humans. Visible radiation is emitted by certain insects (fireflies) and some deep-sea fish due to chemical reactions in the body. Plant uptake carbon dioxide Through the process of photosynthesis and the release of oxygen, it contributes to the maintenance of biological life on Earth. Visible radiation is also used when illuminating 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 wavelengths of 3.8 ∙ 10 -7 - 3 ∙ 10 -9 m ( = 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 influence of visible light, Ritter discovered that silver blackens even more effectively in the region beyond the violet end of the spectrum, where visible radiation is absent. The invisible radiation that caused this blackening was called ultraviolet radiation.

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

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

 = 230 nm, conventional 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 humans, activating the synthesis of vitamin D in the body, as well as causing tanning. A large dose of ultraviolet radiation can cause skin burns and cancer (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 forensic science (photographs reveal forgeries of documents), in art history (with the help of ultraviolet rays you can detect traces of restoration in paintings that are invisible to the eye). Window glass practically does not transmit ultraviolet radiation, because 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 closed window.

The human eye does not see ultraviolet radiation because... The cornea of ​​the eye and the eye lens absorb ultraviolet radiation. Ultraviolet radiation is visible to some animals. For example, a pigeon navigates 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 - 1 0 -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 source of X-ray radiation is an X-ray tube, in which electrons accelerated by an electrical field bombard a metal anode. X-rays can be produced by bombarding a target with high-energy ions. Some radioactive isotopes and synchrotrons - electron storage devices - can also serve as sources of X-ray radiation. Natural sources of X-ray radiation are the Sun and other space objects

Images of objects in X-ray radiation are obtained on 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 ability, X-ray radiation is used in X-ray diffraction analysis (studying the structure of a crystal lattice), in studying the structure of molecules, detecting defects in samples, in medicine (X-rays, fluorography, treatment cancer diseases), in flaw detection (detection of defects in castings, rails), in art history (detection of ancient paintings hidden under a layer of late painting), in astronomy (when studying X-ray sources), and forensics. A large dose of X-ray radiation leads to burns and changes in the structure of human blood. Creation of X-ray receivers and placement of them on space stations made it possible to detect X-ray emission from hundreds of stars, as well as shells supernovae and entire galaxies.

(Slide 11)

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

While studying the radiation of radium in a strong magnetic field, Villar discovered short-wave electromagnetic radiation that does not deflect, like light, magnetic field. It was called gamma radiation. Gamma radiation is associated with nuclear processes, radioactive decay phenomena 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 and 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 various types of electromagnetic radiation.

If you mentally arrange these types according to increasing frequency or decreasing wavelength, you will get a wide continuous spectrum - a scale of electromagnetic radiation (teacher shows scale). TO dangerous species Radiations 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 the 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 at 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 finish working 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.

Wave properties appear more clearly at low frequencies and less clearly at high frequencies. Conversely, quantum properties appear more clearly at high frequencies and less clearly at low frequencies.

The shorter the wavelength, the brighter the quantum properties appear, and the longer the wavelength, the brighter the wave properties appear.

All this serves as confirmation of the law of dialectics (the transition of quantitative changes into qualitative ones).

Abstract (learn), fill in the table

last column (effect of EMR on humans) 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 it discovered by?

5. Source

6. Receiver (indicator)

7. Application

8. Effect on humans

TABLE “ELECTROMAGNETIC WAVE SCALE”

Name of radiation

Wavelength

Frequency

Opened by

Source

Receiver

Application

Effect on humans

The radiations differ from each other:

• by method of receipt;
• by registration method.

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

Short-wave radiation reveals the properties of particles.

Low frequency vibrations

Wavelength (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 high (industrial) frequency (200 Hz)

Telephone networks (5000Hz)

Sound generators (microphones, loudspeakers)

Receiver

Electrical devices and motors

History of discovery

Oliver Lodge (1893), Nikola Tesla (1983)

Application

Cinema, radio 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

History of discovery

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

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

Average- Radiotelegraphy and radiotelephone communications, radio broadcasting, radio navigation

Short- amateur radio communications

VHF- space radio communications

UHF- television, radar, radio relay communications, cellular telephone communications

SMV- radar, radio relay communications, celestial navigation, satellite television

MMV- 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: candle, stove, radiator, electric incandescent lamp

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

Receiver

Thermoelements, bolometers, photocells, photoresistors, photographic films

History of discovery

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

Application

In forensic science, photographing earthly 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, alarm systems for protecting premises, 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, thermocouples

History of discovery

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

Contains sunlight

Gas discharge lamps with quartz tube

Emitted by all solids with a temperature greater than 1000 ° C, luminous (except mercury)

Receiver

Photocells,

Photomultipliers,

Luminescent substances

History of discovery

Johann Ritter, Layman

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

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

Solar corona

Receiver

Camera roll,

The glow of some crystals

History of discovery

V. Roentgen, R. Milliken

Application

Diagnostics and treatment of diseases (in medicine), Flaw detection (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 converting matter into radiation

Receiver

counters

History of discovery

Paul Villard (1900)

Application

Flaw detection

Process control

Research of nuclear processes

Therapy and diagnostics in medicine

GENERAL PROPERTIES OF ELECTROMAGNETIC RADIATIONS

physical nature

all radiation is the same

all radiations spread

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.
• Wave properties appear more clearly at low frequencies and less clearly at high frequencies. Conversely, quantum properties appear more clearly at high frequencies and less clearly at low frequencies.
• The shorter the wavelength, the brighter the quantum properties appear, and the longer the wavelength, the brighter the wave properties appear.

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

Electromagnetic waves are classified by wavelength λ or associated wave frequency f. Note also that these parameters characterize not only wave, but also quantum properties electromagnetic field. Accordingly, in the first case, the electromagnetic wave is described by the classical laws studied in this course.

Let's consider the concept of the spectrum of electromagnetic waves. 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:

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

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

Let's consider the spectrum of electromagnetic waves in more detail.

Low frequency waves

Low frequency waves are electromagnetic waves whose oscillation frequency does not exceed 100 kHz). It is this frequency range that is traditionally used in electrical engineering. In industrial power generation, a frequency of 50 Hz is used, at which transmission occurs electrical energy along lines and voltage conversion by transformer devices. In aviation and ground transportation, 400 Hz is often used, which offers weight advantages electric machines and transformers 8 times compared to the frequency of 50 Hz. The latest generations of switching power supplies use alternating current transformation frequencies of units and tens of kHz, which makes them compact and energy-rich.
The fundamental difference between the low-frequency range and higher frequencies is the drop in the speed of electromagnetic waves in proportion to the square root of their frequency from 300 thousand km/s at 100 kHz to approximately 7 thousand km/s at 50 Hz.

Radio waves

Radio waves are electromagnetic waves whose wavelengths are greater than 1 mm (frequency less than 3 10 11 Hz = 300 GHz) and less than 3 km (above 100 kHz).

Radio waves are divided into:

1. Long waves in the length range from 3 km to 300 m (frequency in the range 10 5 Hz - 10 6 Hz = 1 MHz);

2. Medium waves in the length range from 300 m to 100 m (frequency in the range 10 6 Hz -3*10 6 Hz = 3 MHz);

3. Short waves in the wavelength range from 100m to 10m (frequency in the range 310 6 Hz-310 7 Hz=30 MHz);

4. Ultrashort waves with a wavelength less than 10m (frequency greater than 310 7 Hz = 30 MHz).

Ultrashort waves, in turn, are divided into:

A) meter waves;

B) centimeter waves;

B) millimeter waves;

Waves with a wavelength less than 1 m (frequency less than 300 MHz) are called microwaves or ultra-high frequency waves (microwave waves).

Because of large values radio wavelengths compared to the sizes of atoms, the propagation of radio waves can be considered without taking into account the atomic structure of the medium, i.e. phenomenologically, as is customary when constructing Maxwell's theory. The quantum properties of radio waves appear only for the shortest waves adjacent to the infrared part of the spectrum and during the propagation of the so-called. ultrashort pulses with a duration of the order of 10 -12 sec - 10 -15 sec, comparable to the time of electron oscillations inside atoms and molecules.
The fundamental difference between radio waves and higher frequencies is a different thermodynamic relationship between the wavelength of the wave carrier (ether), equal to 1 mm (2.7°K), and the electromagnetic wave propagating in this medium.

Biological effects of radio wave radiation

The terrible sacrificial experience of using powerful radio wave radiation in radar technology showed the specific effect of radio waves depending on the wavelength (frequency).

The destructive effect on the human body is not so much the average as the peak radiation power, at which irreversible phenomena occur in protein structures. For example, the power of continuous radiation from the magnetron of a microwave oven (microwave), amounting to 1 kW, affects only food in a small closed (shielded) volume of the oven, and is almost safe for a person nearby. The power of a radar station (radar) of 1 kW of average power emitted by short pulses with a duty cycle of 1000:1 (the ratio of the repetition period to the pulse duration) and, accordingly, a pulse power of 1 MW, is very dangerous for human health and life at a distance of up to hundreds meters from the emitter. In the latter, of course, the direction of the radar radiation also plays a role, which emphasizes the destructive effect of pulsed rather than average power.

Exposure to meter waves

High-intensity meter waves emitted by pulse generators of meter radar stations (radars) with a pulse power of more than a megawatt (such as the P-16 early warning station) and commensurate with the length of the spinal cord of humans and animals, as well as the length of axons, disrupt conductivity these structures, causing diencephalic syndrome (HF disease). The latter leads to the rapid development (over a period of several months to several years) of complete or partial (depending on the received pulse dose of radiation) irreversible paralysis of a person’s limbs, as well as disruption of the innervation of the intestines and other internal organs.

Impact of decimeter waves

Decimeter waves are comparable in wavelength to blood vessels, covering such human and animal organs as the lungs, liver and kidneys. This is one of the reasons why they cause the development of “benign” tumors (cysts) in these organs. Developing on the surface of blood vessels, these tumors lead to the cessation of normal blood circulation and disruption of organ function. If such tumors are not surgically removed in time, the death of the body occurs. Decimeter waves of dangerous intensity levels are emitted by the magnetrons of such radars as the P-15 mobile air defense radar, as well as the radar of some aircraft.

Exposure to centimeter waves

Powerful centimeter waves cause diseases such as leukemia - “white blood”, as well as other forms of malignant tumors in humans and animals. Waves of intensity sufficient for the occurrence of these diseases are generated by the centimeter range radars P-35, P-37 and almost all aircraft radars.

Infrared, light and ultraviolet radiation

Infrared, light, ultraviolet radiation amounts to optical region of the spectrum of electromagnetic waves in the broad sense of the word. This spectrum occupies the range of electromagnetic wavelengths in the range from 2·10 -6 m = 2 μm to 10 -8 m = 10 nm (frequency from 1.5·10 14 Hz to 3·10 16 Hz). The upper limit of the optical range is determined by the long-wave limit of the infrared range, and the lower limit by the short-wave limit of the ultraviolet (Fig. 2.14).

The proximity of the spectral regions of the listed waves determined the similarity of the methods and instruments used to study them and practical application. Historically, lenses, diffraction gratings, prisms, diaphragms, and optically active substances included in various optical devices (interferometers, polarizers, modulators, etc.) were used for these purposes.

On the other hand, radiation from the optical region of the spectrum has general patterns of transmission of various media, which can be obtained using geometric optics, widely used for calculations and construction of both optical devices and optical signal propagation channels. Infrared radiation is visible to many arthropods (insects, spiders, etc.) and reptiles (snakes, lizards, etc.) , available for semiconductor sensors(infrared photomatrices), but the thickness of the Earth’s atmosphere does not allow it to pass through, which doesn't allow observe from the surface of the Earth infrared stars - “brown dwarfs”, which make up more than 90% of all stars in the Galaxy.

The frequency width of the optical range is approximately 18 octaves, of which the optical range accounts for approximately one octave (); for ultraviolet - 5 octaves ( ), infrared radiation - 11 octaves (

In the optical part of the spectrum, phenomena caused by the atomic structure of matter become significant. For this reason, along with the wave properties of optical radiation, quantum properties appear.

Light

X-ray and gamma radiation

In the field of X-ray and gamma radiation, the quantum properties of radiation come to the fore.

X-ray radiation occurs when fast charged particles (electrons, protons, etc.) are decelerated, as well as as a result of processes occurring inside the electronic shells of atoms.

Gamma radiation is a consequence of phenomena occurring inside atomic nuclei, as well as as a result nuclear reactions. The boundary between X-ray and gamma radiation is determined conventionally by the value of the energy quantum corresponding to a given frequency of radiation.

X-ray radiation consists of electromagnetic waves with a length from 50 nm to 10 -3 nm, which corresponds to a quantum energy from 20 eV to 1 MeV.

Gamma radiation consists of electromagnetic waves with a wavelength less than 10 -2 nm, which corresponds to a quantum energy greater than 0.1 MeV.

Electromagnetic nature of light

Light is the visible part of the spectrum of electromagnetic waves, the wavelengths of which occupy the range from 0.4 µm to 0.76 µm. Each spectral component of optical radiation can be assigned a specific color. The color of the spectral components of optical radiation is determined by their wavelength. The color of the radiation changes as its wavelength decreases as follows: red, orange, yellow, green, cyan, indigo, violet.

Red light corresponding longest length waves, determines the red boundary of the spectrum. Violet light - corresponds to the violet border.

Natural (daylight, sunlight) light is not colored and represents a superposition of electromagnetic waves from everything visible to humans spectrum Natural light occurs as a result of the emission of electromagnetic waves by excited atoms. The nature of excitation can be different: thermal, chemical, electromagnetic, etc. As a result of excitation, atoms randomly emit electromagnetic waves for approximately 10 -8 seconds. Since the energy spectrum of excitation of atoms is quite wide, electromagnetic waves are emitted from the entire visible spectrum, the initial phase, direction and polarization of which are random. For this reason, natural light is not polarized. This means that the "density" of the spectral components of electromagnetic waves of natural light having mutually perpendicular polarizations is the same.

Harmonic electromagnetic waves in the light range are called monochromatic. For a monochromatic light wave, one of the main characteristics is intensity. Light wave intensity represents the average value of the energy flux density (1.25) transferred by the wave:

Where is the Poynting vector.

Calculation of the intensity of a light, plane, monochromatic wave with amplitude electric field in a homogeneous medium with dielectric and magnetic permeability according to formula (1.35) taking into account (1.30) and (1.32) gives:

Traditionally, optical phenomena are considered using rays. The description of optical phenomena using rays is called geometric-optical. The rules for finding ray trajectories, developed in geometric optics, are widely used in practice for the analysis of optical phenomena and in the construction of various optical instruments.

Let us define a ray based on the electromagnetic representation of light waves. First of all, rays are lines along which electromagnetic waves propagate. For this reason, a ray is a line, at each point of which the averaged Poynting vector of an electromagnetic wave is directed tangentially to this line.

In homogeneous isotropic media, the direction of the average Poynting vector coincides with the normal to the wave surface (equiphase surface), i.e. along the wave vector.

Thus, in homogeneous isotropic media, the rays are perpendicular to the corresponding wavefront of the electromagnetic wave.

For example, consider the rays emitted by a point monochromatic light source. From the point of view of geometric optics, many rays emanate from the source point in the radial direction. From the position of the electromagnetic essence of light, a spherical electromagnetic wave propagates from the source point. At a sufficiently large distance from the source, the curvature of the wave front can be neglected, considering the locally spherical wave to be flat. By dividing the surface of the wave front into a large number of locally flat sections, it is possible to draw a normal through the center of each section, along which a plane wave propagates, i.e. in geometric-optical interpretation ray. Thus, both approaches give the same description of the considered example.

The main task of geometric optics is to find the direction of the beam (trajectory). The trajectory equation is found after solving the variational problem of finding the minimum of the so-called. actions on the desired trajectories. Without going into details of the strict formulation and solution of this problem, we can assume that the rays are trajectories with the shortest total optical length. This statement is a consequence of Fermat's principle.

The variational approach to determining the ray trajectory can also be applied to inhomogeneous media, i.e. such media in which the refractive index is a function of the coordinates of the points of the medium. If we describe the shape of the surface of a wave front in an inhomogeneous medium with a function, then it can be found based on the solution of the partial differential equation, known as the eikonal equation, and in analytical mechanics as the Hamilton-Jacobi equation:

Thus, mathematical basis The geometric-optical approximation of electromagnetic theory consists of various methods for determining the fields of electromagnetic waves on rays, based on the eikonal equation or in some other way. Geometric-optical approximation is widely used in practice in radio electronics to calculate the so-called. quasi-optical systems.

In conclusion, we note that the ability to describe light simultaneously both from wave positions by solving Maxwell’s equations and using rays, the direction of which is determined from the Hamilton-Jacobi equations describing the movement of particles, is one of the manifestations of the apparent dualism of light, which, as is known, led to the formulation logically contradictory principles of quantum mechanics.

In fact, there is no dualism in the nature of electromagnetic waves. As Max Planck showed in 1900 in his classic work"On the normal spectrum of radiation", electromagnetic waves are individual quantized oscillations with a frequency v and energy E=hv, Where h =const, on air. The latter is a superfluid medium that has a stable property of discontinuity in measure h- Planck's constant. When the ether is exposed to energy exceeding hv During radiation, a quantized “vortex” is formed. Exactly the same phenomenon is observed in all superfluid media and the formation of phonons in them - quanta of sound radiation.

For the “copy-and-paste” combination of Max Planck’s discovery in 1900 with the photoelectric effect discovered in 1887 by Heinrich Hertz, in 1921 the Nobel Committee awarded the prize to Albert Einstein

1) An octave, by definition, is the frequency range between an arbitrary frequency w and its second harmonic, equal to 2w.

What does the world tell Suvorov Sergei Georgievich

Electromagnetic radiation scale

Thus, the scale of radiation discovered by man in nature turned out to be very wide. If we go from the longest waves to the shortest, we will see the following picture (Fig. 27). Radio waves come first, they are the longest. These also include radiation discovered by Lebedev and Glagoleva-Arkadyeva; These are ultrashort radio waves. This is followed successively by infrared radiation, visible light, ultraviolet radiation, X-rays and, finally, gamma radiation.

The boundaries between different radiations are very arbitrary: radiations continuously follow one another and even partially overlap each other.

Looking at the scale of electromagnetic waves, the reader can conclude that the radiations we see constitute a very small part of the total spectrum of radiations known to us.

To detect and study invisible radiation, the physicist had to arm himself additional devices. Invisible radiations can be detected by their effects. For example, radio radiation acts on antennas, creating electrical vibrations in them: infrared radiation has the strongest effect on thermal appliances(thermometers), and all other radiations most strongly affect photographic plates, causing them chemical changes. Antennas, thermal instruments, photographic plates are the new “eyes” of physicists for various parts of the electromagnetic wave scale.

Rice. 27. Radiation scale. The grid-shaded area represents the portion of the spectrum visible to the human eye.

The discovery of diverse electromagnetic radiation is one of the most brilliant pages in the history of physics.