The discovery of electromagnetic waves is a remarkable example of the interaction between experiment and theory. It shows how physics has combined seemingly completely dissimilar properties - electricity and magnetism - revealing in them different aspects of the same physical phenomenon - electromagnetic interaction. Today it is one of the four known fundamental physical interactions, which also include the strong and weak nuclear interactions and gravity. The theory of electroweak interaction has already been constructed, which describes electromagnetic and weak nuclear forces from a unified standpoint. There is also the next unifying theory - quantum chromodynamics - which covers the electroweak and strong interactions, but its accuracy is somewhat lower. describe all Fundamental interactions from a unified position have not yet been achieved, although intensive research is being carried out in this direction within the framework of such areas of physics as string theory and quantum gravity.
Electromagnetic waves were theoretically predicted by the great English physicist James Clark Maxwell (probably for the first time in 1862 in his work "On Physical Lines of Force", although detailed description theory was published in 1867). He diligently and with great respect tried to translate into strict mathematical language Michael Faraday's slightly naive pictures describing electrical and magnetic phenomena, as well as the results of other scientists. Having ordered all electrical and magnetic phenomena in the same way, Maxwell discovered a number of contradictions and a lack of symmetry. According to Faraday's law, alternating magnetic fields generate electric fields. But it was not known whether alternating electric fields generate magnetic fields. Maxwell managed to get rid of the contradiction and restore the symmetry of the electric and magnetic fields by introducing an additional term into the equations, which described the appearance of a magnetic field when the electric field changed. By that time, thanks to Oersted's experiments, it was already known that direct current creates a constant magnetic field around the conductor. The new term described another source of the magnetic field, but it could be thought of as some kind of imaginary electric current, which Maxwell called bias current to distinguish from ordinary current in conductors and electrolytes - conduction current. As a result, it turned out that alternating magnetic fields generate electric fields, and alternating electric fields generate magnetic ones. And then Maxwell realized that in such a combination, oscillating electric and magnetic fields can break away from the conductors that generate them and move through vacuum with a certain, but very high speed. He calculated this speed, and it turned out to be about three hundred thousand kilometers per second.
Shocked by the result, Maxwell writes to William Thomson (Lord Kelvin, who, in particular, introduced the absolute temperature scale): “The speed of transverse wave oscillations in our hypothetical medium, calculated from the electromagnetic experiments of Kohlrausch and Weber, coincides so exactly with the speed of light, calculated from optical experiments of Fizeau that we can hardly refuse the conclusion that light consists of transverse vibrations of the same medium, which is the cause of electrical and magnetic phenomena". And further in the letter: “I received my equations while living in the provinces and not suspecting the closeness of the speed of propagation of magnetic effects found by me to the speed of light, so I think that I have every reason to consider the magnetic and luminous media as one and the same medium. ..."
Maxwell's equations go far beyond the scope of a school physics course, but they are so beautiful and concise that they should be placed in a conspicuous place in the physics classroom, because most of the natural phenomena that are significant to humans can be described with just a few lines of these equations. This is how information is compressed when previously dissimilar facts are combined. Here is one of the types of Maxwell's equations in differential representation. Admire.
I would like to emphasize that a discouraging consequence was obtained from Maxwell's calculations: the oscillations of the electric and magnetic fields are transverse (which he himself emphasized all the time). And transverse vibrations propagate only in solids, but not in liquids and gases. By that time, it was reliably measured that the speed of transverse vibrations in solids (simply the speed of sound) is the higher, the, roughly speaking, the harder the medium (the greater the Young's modulus and the lower the density) and can reach several kilometers per second. The speed of the transverse electromagnetic wave was almost a hundred thousand times higher than the speed of sound in solids. And it should be noted that the stiffness characteristic is included in the equation for the speed of sound in a solid under the root. It turned out that the medium through which electromagnetic waves (and light) pass has monstrous elastic characteristics. An extremely difficult question arose: “How can other bodies move through such a solid medium and do not feel it?” The hypothetical medium was called - ether, attributing to it at the same time strange and, generally speaking, mutually exclusive properties - enormous elasticity and extraordinary lightness.
Maxwell's work caused shock among contemporary scientists. Faraday himself wrote with surprise: "At first I was even frightened when I saw such a mathematical force applied to the question, but then I was surprised to see that the question withstands it so well." Despite the fact that Maxwell's views overturned all the ideas known at that time about the propagation of transverse waves and about waves in general, far-sighted scientists understood that the coincidence of the speed of light and electromagnetic waves is a fundamental result, which says that it is here that the main breakthrough awaits physics.
Unfortunately, Maxwell died early and did not live to see reliable experimental confirmation of his calculations. International scientific opinion changed as a result of the experiments of Heinrich Hertz, who 20 years later (1886–89) demonstrated the generation and reception of electromagnetic waves in a series of experiments. Hertz not only obtained the correct result in the quiet of the laboratory, but passionately and uncompromisingly defended Maxwell's views. Moreover, he did not limit himself to experimental proof of the existence of electromagnetic waves, but also investigated their basic properties (reflection from mirrors, refraction in prisms, diffraction, interference, etc.), showing the complete identity of electromagnetic waves with light.
It is curious that seven years before Hertz, in 1879, the English physicist David Edward Hughes (Hughes - D. E. Hughes) also demonstrated to other major scientists (among them was also the brilliant physicist and mathematician Georg-Gabriel Stokes) the effect of propagation of electromagnetic waves in the air. As a result of discussions, scientists came to the conclusion that they see the phenomenon of Faraday's electromagnetic induction. Hughes was upset, did not believe himself, and published the results only in 1899, when the Maxwell-Hertz theory became generally accepted. This example shows that in science persistent dissemination and propaganda of the results obtained is often no less important than the scientific result itself.
Heinrich Hertz summed up the results of his experiments in the following way: "The experiments described, at least, it seems to me, eliminate doubts about the identity of light, thermal radiation and electrodynamic wave motion."
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"Ampere Force" - The orienting action of the MP on the circuit with current is used in electrical measuring instruments of the magnetoelectric system - ammeters and voltmeters. Ampère André Marie. The action of a magnetic field on conductors with current. Ampere power. Under the action of the Ampere force, the coil oscillates along the axis of the loudspeaker in time with current fluctuations. Determine the position of the poles of the magnet that creates the magnetic field. Application of Ampere force.
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“Around us, in ourselves, everywhere and everywhere, forever changing, coinciding and colliding, there are radiations of different wavelengths ... The face of the Earth changes with them, they are largely molded”
V.I.Vernadsky
The learning objectives of the lesson:
- Learn the following elements of incomplete student experience in a single lesson: low-frequency radiation, radio waves, infrared radiation, visible radiation, ultraviolet radiation, x-rays, gamma rays; their application in human life.
- Systematize and generalize knowledge about electromagnetic waves.
Developing objectives of the lesson:
- continue the formation of a scientific worldview based on knowledge of electromagnetic waves.
- show a complex solution of problems based on the knowledge of physics and computer science.
- to promote the development of analytical-synthetic and figurative thinking, for which to encourage students to comprehend and find cause-and-effect relationships.
- to form and develop key competencies: informational, organizational, self-organizing, communication.
- When working in pairs and in a group, to form such important qualities and skills of a student as:
desire to participate in joint activities, confidence in success, a sense of positive emotions from joint activities;
the ability to present yourself and your work;
ability to build business relationship in joint activities in the lesson (accept the goal of joint activities and accompanying instructions to it, share responsibilities, agree on ways to achieve the result of the proposed goal);
analyze and evaluate the experience of interaction.
Educational objectives of the lesson:
- develop taste, focusing on the original design of the presentation with animation effects.
- to cultivate a culture of perception of theoretical material using a computer to gain knowledge about the history of discovery, properties and application of electromagnetic waves
- fostering a sense of pride for their homeland, for domestic scientists who worked in the field of electromagnetic waves, applied them in human life.
Equipment:
Laptop, projector, electronic library "Enlightenment" disk 1 (grades 10-11), materials from the Internet.
Lesson plan:
1. Introductory speech of the teacher.
2. Learning new material.
- Low-frequency electromagnetic radiation: history of discovery, sources and receivers, properties and applications.
- Radio waves: history of discovery, sources and receivers, properties and applications.
- Infrared electromagnetic radiation: history of discovery, sources and receivers, properties and applications.
- Visible electromagnetic radiation: history of discovery, sources and receivers, properties and applications.
- Ultraviolet electromagnetic radiation: history of discovery, sources and receivers, properties and applications.
- X-ray radiation: history of discovery, sources and receivers, properties and applications.
- Gamma radiation: history of discovery, sources and receivers, properties and applications.
Each group at home prepared a table:
Historian studied and recorded in his table the history of the discovery of radiation,
Constructor studied sources and receivers of various types of radiation,
polymath theorist studied the characteristic properties of electromagnetic waves,
Practitioner studied the practical application of electromagnetic radiation in various fields of human activity.
Each student drew 7 tables for the lesson, one of which was filled in by him at home.
Teacher: The EM radiation scale has two sections:
- 1 section - radiation of vibrators;
- Section 2 - radiation of molecules, atoms, nuclei.
Section 1 is divided into 2 parts (range): low-frequency radiation and radio waves.
Section 2 contains 5 ranges: infrared radiation, visible radiation, ultraviolet radiation, X-rays and gamma rays.
We begin the study with low frequency electromagnetic waves, the coordinator of group 1 is given the floor.
Coordinator 1:
Low-frequency electromagnetic radiation is electromagnetic waves with a wavelength of 107 - 105 m
,
Opening history:
For the first time drew attention to the low-frequency
electromagnetic waves Soviet physicist Vologdin V.P., creator of modern high-frequency electrical engineering. He discovered that during the operation of high-frequency induction generators, electromagnetic waves with a length of 500 meters to 30 km arose.
Vologdin V.P.
Sources and Destinations
Low frequency electrical oscillations are generated by generators in electrical networks frequency of 50 Hz, magnetic generators of increased frequency up to 200 Hz, as well as in telephone networks with a frequency of 5000 Hz.
Electromagnetic waves over 10 km are called low-frequency waves. With the help of an oscillatory circuit, electromagnetic waves (radio waves) can be obtained. This proves that there is no sharp boundary between LF and RF. LF waves are generated by electrical machines and oscillatory circuits.
Properties
Reflection, refraction, absorption, interference, diffraction, transverse (waves with a certain direction of vibrations E and B are called polarized),
Fast fading;
Eddy currents are induced in the substance that penetrates low-frequency waves, causing deep heating of this substance.
Application
A low-frequency electromagnetic field induces eddy currents, causing deep heating - this is inductothermy. LF is used in power plants, in engines, in medicine.
Teacher: Tell us about low frequency electromagnetic radiation.
The students are talking.
Teacher: The next band is radio waves, the floor is given to the coordinator 2 .
Coordinator 2:
radio waves
radio waves- these are electromagnetic waves with a wavelength from several km to several mm and a frequency from 105 -1012 Hz.
Discovery history
James Maxwell first spoke about radio waves in his works in 1868. He proposed an equation that describes light and radio waves as waves of electromagnetism.
In 1896, Heinrich Hertz experimentally confirmed
Maxwell's theory, having received radio waves several tens of centimeters long in his laboratory.
On May 7, 1895, A.S. Popov reported to the Russian Physical and Chemical Society about the invention of a device capable of capturing and registering electrical discharges.
On March 24, 1896, using these waves, he transmitted the world's first two-word radiogram "Heinrich Hertz" over a distance of 250m.
In 1924 A.A. Glagoleva-Arkad'eva, with the help of the mass emitter created by her, received even shorter EM waves entering the region of IR radiation.
M.A. Levitskaya, Professor of the Voronezh State University as radiating vibrators, she took metal balls and small wires glued to glass. She received EM waves with a wavelength of 30 microns.
M.V. Shuleikin developed a mathematical analysis of radio communication processes.
B.A. Vvedensky developed the theory of rounding the earth by radio waves.
O.V.Losev discovered the property of a crystal detector to generate undamped oscillations.
Sources and Destinations
RVs are emitted by vibrators (antennas connected to tube or semiconductor generators. Depending on the purpose, generators and vibrators may have a different design, but the antenna always converts the EM waves supplied to it.
In nature, there are natural sources of RS in all frequency bands. These are stars, the Sun, galaxies, metagalaxies.
RS are also generated during some processes occurring in the earth's atmosphere, for example, during a lightning discharge.
RVs are also received by antennas, which convert the EM waves incident on them into electromagnetic oscillations, which then act on the receiver (TV, radio, computer, etc.)
Properties of radio waves:
Reflection, refraction, interference, diffraction, polarization, absorption, short waves are well reflected from the ionosphere, ultrashort waves penetrate the ionosphere.
Impact on human health
According to doctors, the most sensitive systems of the human body to electromagnetic radiation are: nervous, immune, endocrine and sexual.
Study of the impact of radio emission from mobile phones on people gives the first disappointing results.
Back in the early 90s, the American scientist Clark drew attention to the fact that health improves .... radio waves!
In medicine, there is even a direction - magnetotherapy, and some scientists, for example, Doctor of Medical Sciences, Professor V.A. Ivanchenko, uses his medical devices working on this principle for medicinal purposes.
It seems unbelievable, but frequencies have been found that are detrimental to hundreds of microorganisms and protozoa, and at certain frequencies the body is recovering, once you turn on the device for a few minutes, and, depending on a certain frequency, the organs marked as sick restore their functions, come into the normal range.
Protection from negative impact
Far from the last role can be played by personal protective equipment based on textile materials.
Many foreign firms have created fabrics that effectively protect the human body from most types of electromagnetic radiation.
Application of radio waves
Telescope– the giant allows radio measurements.
Complex "Spectrum-M" allows you to analyze any sample in any region of the spectrum: solid, liquid, gaseous.
Unique microendoscope improves the accuracy of the diagnosis.
Radio telescope submillimeter range registers radiation from a part of the universe, which is covered by a layer of cosmic dust.
Compact camera. Advantage: the ability to erase pictures.
Radio engineering methods and devices are used in automation, computer technology, astronomy, physics, chemistry, biology, medicine, etc.
Microwaves are used for fast food preparation. microwave ovens.
Voronezh- the city of radio electronics. Tape recorders and televisions, radios and radio stations, telephone and telegraph, radio and television.
Teacher: Tell me about radio waves. Compare the properties of low frequency radiation with the properties of radio waves.
Pupils tell. Short waves are well reflected from the ionosphere. Ultrashort ones penetrate the ionosphere.
Lesson Objectives:
Lesson type:
Conduct form: lecture with presentation
Karaseva Irina Dmitrievna, 17.12.2017
3355 349
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 a wide range 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. Radio emission research space objects 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. By their own physical properties it is similar to other ranges of the spectrum, being only a small part of the spectrum of electromagnetic waves. radiation that has different length waves (frequencies) in the visible range, has a different physiological effect 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 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 it is possible to detect in the paintings not visible to the eye traces of restoration). Practically does not pass ultra-violet radiation a window glass since. it is absorbed by iron oxide, which is part of the glass. For this reason, even on a hot sunny day, you cannot 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 Villard (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 purpose of the lesson: to provide during the lesson a repetition of the basic laws, properties of electromagnetic waves;
Educational: Systematize the material on the topic, carry out the correction of knowledge, some of its deepening;
Educational: Development of students' oral speech, students' creative skills, logic, memory; cognitive abilities;
Educational: To form students' interest in the study of physics. educate accuracy and skills for the rational use of one's time;
Lesson type: lesson of repetition and correction of knowledge;
Equipment: computer, projector, presentation "Scale of electromagnetic radiation", disk "Physics. Library of visual aids.
During the classes:
1. Explanation of new material.
1. We know that the length of electromagnetic waves is very different: from values of the order of 1013 m (low-frequency oscillations) to 10 -10 m (g-rays). Light is an insignificant part of the wide spectrum of electromagnetic waves. However, it was during the study of this small part of the spectrum that other radiations with unusual properties were discovered.
2. It is customary to highlight low frequency radiation, radio radiation, infrared rays, visible light, ultraviolet rays, x-rays andg radiation. With all these radiations except g-radiation, you are already familiar. The shortest g radiation emitted by atomic nuclei.
3. There is no fundamental difference between individual radiations. All of them are electromagnetic waves generated by charged particles. Electromagnetic waves are detected, ultimately, by their action on charged particles . In a vacuum, radiation of any wavelength travels at a speed of 300,000 km/s.
The boundaries between individual areas of the radiation scale are very arbitrary.
4. Radiation of different wavelengths differ from each other in the way they receiving(antenna radiation, thermal radiation, radiation during deceleration of fast electrons, etc.) and methods of registration.
5. All of the listed types of electromagnetic radiation are also generated by space objects and are successfully studied with the help of rockets, artificial Earth satellites and spacecraft. First of all, this applies to X-ray and g radiation that is strongly absorbed by the atmosphere.
6. As the wavelength decreases quantitative differences in wavelengths lead to significant qualitative differences.
7. Radiations of different wavelengths differ greatly from each other in terms of their absorption by matter. Shortwave radiation (X-ray and especially g rays) are weakly absorbed. Substances that are opaque to optical wavelengths are transparent to these radiations. The reflection coefficient of electromagnetic waves also depends on the wavelength. But the main difference between longwave and shortwave radiation is that shortwave radiation reveals the properties of particles.
Let's summarize the knowledge about waves and write down everything in the form of tables.
1. Low frequency oscillations
| Low frequency vibrations | |
| Wavelength(m) | 10 13 - 10 5 |
| Frequency Hz) | 3 10 -3 - 3 10 3 |
| Energy(EV) | 1 - 1.24 10 -10 |
| Source | Rheostatic alternator, dynamo, hertz vibrator, Generators in electrical networks (50 Hz) Machine generators of increased (industrial) frequency (200 Hz) Telephone networks (5000Hz) Sound generators (microphones, loudspeakers) |
| Receiver | Electrical appliances and motors |
| Discovery history | Lodge (1893), Tesla (1983) |
| Application | Cinema, broadcasting (microphones, loudspeakers) |
2. Radio waves
| radio waves | |
| Wavelength(m) | 10 5 - 10 -3 |
| Frequency Hz) | 3 10 3 - 3 10 11 |
| Energy(EV) | 1.24 10-10 - 1.24 10 -2 |
| Source | Oscillatory circuit Macroscopic vibrators |
| Receiver | Sparks in the gap of the receiving vibrator The glow of a gas discharge tube, coherer |
| Discovery history | Feddersen (1862), Hertz (1887), Popov, Lebedev, Rigi |
| Application | Extra long- Radio navigation, radiotelegraph communication, transmission of weather reports Long– Radiotelegraph and radiotelephone communications, radio broadcasting, radio navigation Medium- Radiotelegraphy and radiotelephony radio broadcasting, radio navigation Short- amateur radio VHF- space radio communications DMV- television, radar, radio relay communication, cellular telephone communication SMV- radar, radio relay communication, astronavigation, satellite television IIM- radar |
| Infrared radiation | |
| Wavelength(m) | 2 10 -3 - 7.6 10 -7 |
| Frequency Hz) | 3 10 11 - 3 10 14 |
| Energy(EV) | 1.24 10 -2 - 1.65 |
| Source | Any heated body: a candle, a stove, a water heating battery, an electric incandescent lamp A person emits electromagnetic waves with a length of 9 10 -6 m |
| Receiver | Thermoelements, bolometers, photocells, photoresistors, photographic films |
| Discovery history | Rubens and Nichols (1896), |
| Application | In criminology, photographing terrestrial objects in fog and darkness, binoculars and sights for shooting in the dark, heating the tissues of a living organism (in medicine), drying wood and painted car bodies, alarms for the protection of premises, an infrared telescope, |
4. Visible radiation
5. Ultraviolet radiation
| Ultraviolet radiation | |
| Wavelength(m) | 3.8 10 -7 - 3 10 -9 |
| Frequency Hz) | 8 10 14 - 10 17 |
| Energy(EV) | 3.3 - 247.5 EV |
| Source | Included in sunlight Discharge lamps with quartz tube Radiated by all solids whose temperature is more than 1000 ° C, luminous (except mercury) |
| Receiver | photocells, photomultipliers, Luminescent substances |
| Discovery history | Johann Ritter, Leiman |
| Application | Industrial electronics and automation, fluorescent lamps, Textile production Air sterilization |
6. x-ray radiation
| x-ray radiation | |
| Wavelength(m) | 10 -9 - 3 10 -12 |
| Frequency Hz) | 3 10 17 - 3 10 20 |
| Energy(EV) | 247.5 - 1.24 105 EV |
| Source | Electronic X-ray tube (voltage at the anode - up to 100 kV. pressure in the cylinder - 10 -3 - 10 -5 N / m 2, cathode - incandescent filament. Anode material W, Mo, Cu, Bi, Co, Tl, etc. Η = 1-3%, radiation - high energy quanta) solar corona |
| Receiver | Camera roll, Glow of some crystals |
| Discovery history | W. Roentgen, Milliken |
| Application | Diagnosis and treatment of diseases (in medicine), Defectoscopy (control of internal structures, welds) |
7. Gamma radiation
Conclusion
The entire scale of electromagnetic waves is evidence that all radiation has both quantum and wave properties. Quantum and wave properties in this case do not exclude, but complement each other. The wave properties are more pronounced at low frequencies and less pronounced at high frequencies. Conversely, quantum properties are more pronounced at high frequencies and less pronounced at low frequencies. The shorter the wavelength, the more pronounced the quantum properties, and the longer the wavelength, the more pronounced the wave properties. All this confirms the law of dialectics (transition of quantitative changes into qualitative ones).
Literature:
- "Physics-11" Myakishev
- Disk “Lessons of physics of Cyril and Methodius. Grade 11 "()))" Cyril and Methodius, 2006)
- Disk "Physics. Library of visual aids. Grades 7-11 "((1C: Bustard and Formosa 2004)
- Internet resources
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