Lesson objectives:
Lesson type:
Form of carrying out: lecture with presentation
Karaseva Irina Dmitrievna, 17.12.2017
2492 287
Development content
Lesson summary on the topic:
Types of radiation. Scale electromagnetic waves
Lesson developed
teacher of GU LPR "LOUSOSH No. 18"
Karasevoy 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 effect of various types of radiation on a person; systematize the material on the topic and deepen the knowledge of students about electromagnetic waves; develop oral speech learners, learners' creative skills, logic, memory; cognitive ability; to form students' interest in the study of physics; bring up accuracy, diligence.
Lesson type: lesson in the formation of new knowledge.
Form of carrying out: lecture with presentation
Equipment: computer, multimedia projector, presentation “Types of radiation.
Scale of electromagnetic waves "
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, not noticing the waves penetrating the surrounding space. 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, mankind during the 20th century has mastered and put at its service its most diverse types.
Statement of the topic and objectives 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. 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. Band name
2. Wavelength
3. Frequency
4. Who was discovered
5. Source
6. Receiver (indicator)
7. Application
8. Action on humans
As you study the topic, you must complete the following table:
Table "Scale of electromagnetic radiation"
| Name radiation | Wavelength | Frequency | Who was open | A source | Receiver | Application | Action on humans |
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 makes up a tiny fraction of the wide spectrum of electromagnetic waves. Nevertheless, it was by studying 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 - radiation emits atomic nuclei.
There is no fundamental difference between individual emissions. All of them are electromagnetic waves generated by charged particles. Detect electromagnetic waves, 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 the individual regions of the radiation scale are rather arbitrary.
(Slide 4)
Radiation of various wavelengths differ from each other in the way they receiving(antenna radiation, thermal radiation, radiation during deceleration of fast electrons, etc.) and registration methods.
All of these types of electromagnetic radiation are also generated by space objects and are successfully investigated 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.
Radiation of different wavelengths are very different from each other in their absorption by matter. Shortwave radiation (X-rays and especially -rays) are poorly absorbed. Substances that are opaque to waves in the optical range are transparent to these radiations. The reflectance 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 is alternating current generators. They are used for melting and hardening 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. The source radio waves, as well as low frequency radiation is alternating current... The source is also a radio frequency generator, stars, including the Sun, galaxies and metagalaxies. The indicators are a Hertz vibrator, an oscillatory circuit.
High frequency radio waves compared to low-frequency radiation leads to a noticeable emission of radio waves into space. This allows them to be used to transmit information over different distances. Speech, music (broadcasting), telegraph signals (radio communication), images of various objects (radar) are transmitted.
Radio waves are used to study the structure of matter and the properties of the medium in which they propagate. The study of radio emission from space objects is the subject of radio astronomy. In radio meteorology, processes are studied based on the characteristics of the 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 that the thermometer warms up most outside the visible light region (behind the red region). Invisible radiation given its place in the spectrum, it 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 to dry wood, food and various paints and varnishes(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. Infrared beams are used to aim projectiles and missiles at a target, to detect a camouflaged enemy. These rays make it possible to determine the difference in temperatures of individual sections of the surface of planets, the structural features of the molecules of matter ( 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 forensic science when detecting fakes. When exposed to humans, 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 rather 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, which change their position in space, as well as free charges, moving rapidly. This part of the spectrum gives a person maximum information about the world around him. In terms of its physical properties, it is similar to other ranges of the spectrum, being only a small part of the spectrum of electromagnetic waves. Radiation, which has different wavelengths (frequencies) in the range of visible radiation, has different physiological effects on the retina of the human eye, causing a psychological sensation of light. Color is not a property of an electromagnetic light wave in itself, but a manifestation of an electrochemical action physiological system human: eyes, nerves, brain. There are approximately seven primary colors distinguishable by the human eye in the visible range (in ascending order of radiation frequency): red, orange, yellow, green, cyan, blue, violet. Memorizing the sequence of the primary colors of the spectrum is facilitated by the 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 interfere with the chemical reactions in plants (photosynthesis) and in animals and humans. 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. Also, visible radiation is 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, invisible to the eye electromagnetic radiation occupying the spectral region between visible and X-ray radiation within the wavelength range 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. While studying the blackening of silver chloride by 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 radiation.
The source of ultraviolet radiation is the valence electrons of atoms and molecules, also rapidly moving free charges.
Radiation heated to temperatures - 3000 K solids contains a noticeable proportion of continuous 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 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-wavelength part of their radiation ( 290 nm) reaches the earth's surface. To register 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 detectors are used that use the ability of ultraviolet radiation to cause ionization and photoelectric effect: photodiodes, ionization chambers, photon counters, photomultipliers.
In small doses, ultraviolet radiation has a beneficial, health-improving effect on humans, activating the synthesis of vitamin D in the body, as well as causing sunburn. A large dose of ultraviolet radiation can cause skin burns and cancerous growths (80% curable). In addition, excessive UV radiation weakens immune system organism, contributing to the development of certain diseases. Ultraviolet radiation also has a bactericidal effect: under the influence of this radiation, pathogenic bacteria die.
Ultraviolet radiation is used in fluorescent lamps, in forensic science (forgeries are detected from photographs), in art history (with the help of ultraviolet rays traces of restoration that are not visible to the eye can be found in the paintings). Virtually impervious to ultraviolet radiation 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 the room with the window closed.
The human eye cannot see ultraviolet radiation because the cornea and the eye lens absorb ultraviolet light. Some animals see ultraviolet radiation. For example, a dove is guided by the Sun even in cloudy weather.
(Slide 10)
X-ray radiation - is electromagnetic ionizing radiation that occupies the spectral region between gamma and ultraviolet radiation within the wavelength range from 10 -12 - 1 0 -8 m (frequencies 3 * 10 16 - 3-10 20 Hz). X-rays were discovered in 1895 by the German physicist W. K. Roentgen. The most common X-ray source is an X-ray tube in which electrons accelerated by an electric zero bombard a metal anode. X-rays can be produced by bombarding a target with high-energy ions. Some radioactive isotopes, synchrotrons - electron storage devices can also serve as sources of X-ray radiation. Natural sources X-ray radiation is the Sun and other space objects
X-ray images of objects 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, microchannel plates. Due to its high penetrating power x-ray used in X-ray structural analysis (study of the structure of the crystal lattice), in the study of the structure of molecules, detection of defects in samples, in medicine (X-rays, fluorography, cancer treatment), in defectoscopy (detection of defects in castings, rails), in art history (detection of old painting hidden under a layer of late painting), in astronomy (in the study of X-ray sources), forensic science. A large dose of X-ray radiation leads to burns and changes in the structure of the human blood. The creation of X-ray detectors and their placement on space stations made it possible to detect X-ray radiation 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.
By studying the radiation of radium in a strong magnetic field, Willard discovered shortwave electromagnetic radiation, which does not deflect, like light, magnetic field... It was called gamma radiation. Gamma radiation is associated with nuclear processes, the phenomena of radioactive decay that occur with certain substances, both on Earth and in space. Gamma radiation can be recorded using ionization and bubble chambers, as well as using special photographic emulsions. They are used in the study of nuclear processes, in non-destructive testing. 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 decompose these types in increasing frequency or decreasing wavelength, you get a wide continuous spectrum - the scale of electromagnetic radiation (the teacher shows the scale). TO dangerous species radiation includes: gamma radiation, X-rays and ultraviolet radiation, the rest are safe.
The division of electromagnetic radiation into ranges is conditional. There is no clear border 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 emission scale have general properties:
the physical nature of all radiations is the same
all radiation propagates in vacuum at the same speed equal to 3 * 10 8 m / s
all emissions 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.
In this case, quantum and wave properties do not exclude, but complement each other.
The wave properties are brighter at low frequencies and less bright at high frequencies. Conversely, quantum properties are more pronounced at high frequencies and less brightly 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 a confirmation of the law of dialectics (transition of quantitative changes to qualitative ones).
Abstract (learn), fill in the table
the last column (the effect of EMR on a person) and
prepare a message on the use of EMP
Development content
GU LPR "LOUSOSH No. 18"
Luhansk
Karaseva I.D.
GENERALIZED RADIATION STUDY PLAN
1. Band name.
2. Wavelength
3. Frequency
4. Who was discovered
5. Source
6. Receiver (indicator)
7. Application
8. Action on humans
TABLE "SCALE OF ELECTROMAGNETIC WAVES"
Radiation name
Wavelength
Frequency
Opened by
A source
Receiver
Application
Action on humans
Emissions differ from each other:
- by the method of receipt;
- by the registration method.
Quantitative differences in wavelengths lead to significant qualitative differences, they are absorbed in different ways by matter (short-wave radiation - X-rays and gamma radiation) - are weakly absorbed.
Shortwave radiation exhibits the properties of particles.
Low frequency vibrations
Wavelength (m)
10 13 - 10 5
Frequency Hz)
3 · 10 -3 - 3 · 10 5
A source
Rheostat 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, radio broadcasting (microphones, loudspeakers)
Radio waves
Wavelength (m)
Frequency Hz)
10 5 - 10 -3
A source
3 · 10 5 - 3 · 10 11
Oscillatory circuit
Macroscopic vibrators
Stars, galaxies, metagalaxies
Receiver
Discovery history
Sparks in the gap of the receiving vibrator (Hertz vibrator)
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 communication, radio broadcasting, radio navigation
Average- Radiotelegraphy and radiotelephony radio broadcasting, radio navigation
Short- radio amateur communication
VHF- space radio communication
UHF- television, radar, radio relay communication, cellular telephone communication
CMB- radar, radio relay communication, astronavigation, satellite TV
MMV- radar
Infrared radiation
Wavelength (m)
2 · 10 -3 - 7,6∙10 -7
Frequency Hz)
3∙10 11 - 3,85∙10 14
A source
Any heated body: a candle, a stove, a water heating battery, electric lamp incandescence
A person emits electromagnetic waves 9 · 10 -6 m
Receiver
Thermocouples, bolometers, photocells, photoresistors, photographic films
Discovery history
W. Herschel (1800), G. Rubens and E. Nichols (1896),
Application
In forensic science, photographing terrestrial objects in fog and darkness, binoculars and sights for shooting in the dark, warming up tissues of a living organism (in medicine), drying wood and painted car bodies, alarms when guarding premises, infrared telescope.
Visible radiation
Wavelength (m)
6,7∙10 -7 - 3,8 ∙10 -7
Frequency Hz)
4∙10 14 - 8 ∙10 14
A source
Sun, incandescent lamp, fire
Receiver
Eye, photographic plate, photocells, thermocouples
Discovery history
M. Melloni
Application
Vision
Biological life
Ultraviolet radiation
Wavelength (m)
3,8 ∙10 -7 - 3∙10 -9
Frequency Hz)
8 ∙ 10 14 - 3 · 10 16
A source
Part of the sunlight
Quartz tube gas discharge lamps
Emitted by all solids with a temperature of more than 1000 ° C, luminous (except for mercury)
Receiver
Photocells,
Photomultipliers,
Luminescent substances
Discovery history
Johann Ritter, Lyman
Application
Industrial electronics and automation,
Fluorescent lamps,
Textile production
Air sterilization
Medicine, cosmetology
X-ray radiation
Wavelength (m)
10 -12 - 10 -8
Frequency Hz)
3∙10 16 - 3 · 10 20
A source
Electronic X-ray tube (voltage at the anode - up to 100 kV, cathode - incandescent filament, radiation - high energy quanta)
Solar crown
Receiver
Camera roll,
Some crystals glow
Discovery history
W. Roentgen, R. Milliken
Application
Diagnostics and treatment of diseases (in medicine), Defectoscopy (control internal structures, welds)
Gamma - radiation
Wavelength (m)
3,8 · 10 -7 - 3∙10 -9
Frequency Hz)
8∙10 14 - 10 17
Energy (EE)
9,03 10 3 – 1, 24 10 16 Ev
A source
Radioactive atomic nuclei nuclear reactions, processes of transformation of matter into radiation
Receiver
counters
Discovery history
Paul Villard (1900)
Application
Flaw detection
Control of technological processes
Research of nuclear processes
Therapy and diagnostics in medicine
GENERAL PROPERTIES OF ELECTROMAGNETIC RADIATIONS
physical nature
of all emissions is the same
all radiations spread
in a vacuum at the same speed,
equal to the speed of light
all radiations detect
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.
- In this case, quantum and wave properties do not exclude, but complement each other.
- The wave properties are brighter at low frequencies and less bright at high frequencies. Conversely, quantum properties are more pronounced at high frequencies and less brightly 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 (the effect of EMR on a person)
- prepare a message on the use of EMP
Everything electromagnetic fields are created by rapidly moving charges. A stationary charge creates only an electrostatic field. In this case, there are no electromagnetic waves. In the simplest case, the source of radiation is a charged particle that oscillates. Because electric charges can vibrate at any frequency, then the frequency spectrum of electromagnetic waves is unlimited. This is how electromagnetic waves differ from sound waves. The classification of these waves by frequency (in hertz) or wavelength (in meters) is represented by a scale of electromagnetic waves (Fig. 1.10). Although the entire spectrum is divided into regions, the boundaries between them are outlined conventionally. The regions follow one another continuously, and in some cases overlap. The difference in properties becomes noticeable only when the wavelengths differ by several orders of magnitude.
Let us consider the qualitative characteristics of electromagnetic waves of different frequency ranges and methods of their excitation and registration.
Radio waves. All electromagnetic radiation, the wavelength of which is more than half a millimeter, refers to radio waves. Radio waves correspond to the frequency range from 3 · 10 3 to 3 · 10 14 Hz... Allocate the region of long waves more than 1000 m, medium - from 1,000 m up to 100 m, short - from 100 m to 10 m and ultrashort - less than 10 m.
 |
Radio waves can travel long distances in the earth's atmosphere with virtually no loss. With their help, radio and television signals are transmitted. The propagation of radio waves over the earth's surface is influenced by the properties of the atmosphere. The role of the atmosphere is determined by the presence in it upper layers ionosphere. The ionosphere is ionized top part atmosphere. A feature of the ionosphere is a high concentration of free charged particles - ions and electrons. The ionosphere for all radio waves, starting from very long (λ ≈ 10 4 m) and up to short (λ ≈ 10 m) is a reflective medium. Due to the reflection from the Earth's ionosphere, radio waves of the meter and kilometer range are used for broadcasting and radio communication at long distances, providing signal transmission over arbitrarily large distances within the Earth. However, today this type of communication is becoming a thing of the past thanks to the development of satellite communications.
UHF waves cannot bend around the earth's surface, which limits their reception area to the direct propagation region, which depends on the antenna height and transmitter power. But even in this case, the role of radio wave reflectors, which the ionosphere plays in relation to meter waves, is taken over by satellite repeaters.
Electromagnetic waves in radio wave ranges are emitted by antennas of radio stations, in which electromagnetic oscillations are excited using high and ultrahigh frequency generators (Fig. 1.11).
However, in exceptional cases, radio frequency waves can be generated by microscopic charge systems such as electrons from atoms and molecules. So, an electron in a hydrogen atom is capable of emitting an electromagnetic wave with a length (this length corresponds to the frequency Hz, which belongs to the microwave portion of the radio range). In the unbound state, hydrogen atoms are found mainly in the interstellar gas. Moreover, each of them emits on average once every 11 million years. Nevertheless, cosmic radiation is quite observable, since a lot of atomic hydrogen is scattered in world space.
It is interesting
Radio waves are weakly absorbed by the environment, therefore, studying the Universe in the radio range is very informative for astronomers. Since the 40s. XX century, radio astronomy is rapidly developing, the task of which is to study celestial bodies by their radio emission. Successful flights of interplanetary space stations to the Moon, Venus and other planets have demonstrated the capabilities of modern radio engineering. So, signals from the descent vehicle from the planet Venus, the distance to which is about 60 million kilometers, are received by ground stations 3.5 minutes after their departure.
An unusual radio telescope began to operate 500 km north of San Francisco, California. Its task is to search for extraterrestrial civilizations.
| The picture is taken from the site top.rbc.ru |
The Allen Telescope Array (ATA) is named after Microsoft co-founder Paul Allen, who donated $ 25 million to build it. At present, ATA consists of 42 antennas with a diameter of 6 m, but their number is planned to be increased to 350.
The creators of the ATA hope to catch signals from other living things in the Universe by about 2025. The telescope is also expected to help collect additional data on such phenomena as supernovae, "black holes" and various exotic astronomical objects, the existence of which is theoretically predicted, but in practice was not observed.
The center is jointly run by the University of California Berkeley Radio Astronomy Laboratory and the SETI Institute for the search for extraterrestrial life. ATA's technical capabilities greatly enhance SETI's ability to capture intelligent life signals.
Infrared radiation. The infrared range corresponds to wavelengths from 1 mm up to 7 · 10 –7 m... Infrared radiation occurs during the accelerated quantum movement of charges in molecules. This accelerated movement occurs when the molecule rotates and its atoms vibrate.
| Rice. 1.12 |
The presence of infrared waves was established in 1800 by William Herschel. V. Herschel accidentally discovered that the thermometers used by him also heat up beyond the red end of the visible spectrum. The scientist concluded that there is electromagnetic radiation that continues the spectrum of visible radiation behind red light. He called this radiation infrared. It is also called thermal, since infrared rays are emitted by any heated body, even if it does not glow for the eye. You can easily feel the radiation from a hot iron even when it's not hot enough to glow. Heaters in an apartment emit infrared waves, which cause noticeable heating of the surrounding bodies (Fig. 1.12). Infrared radiation is heat, which is given off to varying degrees by all heated bodies (the sun, fire flame, heated sand, fireplace).
 Rice. 1.13 |
A person feels infrared radiation directly with his skin - as heat emanating from a fire or a red-hot object (Fig. 1.13). Some animals (for example, burrowing vipers) even have senses that allow them to locate a warm-blooded victim by the infrared radiation of its body. A person creates infrared radiation in the range of 6 micron to 10 micron... Molecules that make up skin human, "resonate" at infrared frequencies. Therefore, it is infrared radiation that is predominantly absorbed, warming us.
The Earth's atmosphere allows very little infrared radiation to pass through. It is absorbed by air molecules, and especially by carbon dioxide molecules. The greenhouse effect is also caused by carbon dioxide, due to the fact that a heated surface emits heat, which does not go back into space. There is little carbon dioxide in space, so heat rays pass through dust clouds with little loss.
To register infrared radiation in the region of the spectrum close to the visible (from l = 0.76 micron up to 1.2 micron), use the photographic method. In other ranges, thermocouples are used, semiconductor bolometers, consisting of semiconductor strips. The resistance of semiconductors when illuminated with infrared radiation changes, which is recorded in the usual way.
Since most objects on the Earth's surface emit energy in the infrared range of waves, infrared detectors play an important role in modern technologies detection. Night vision devices allow you to detect not only people, but also equipment and structures that have heated up during the day and give off their heat at night. environment in the form of infrared rays. Infrared detectors are widely used by rescue services, for example, to detect living people under rubble after earthquakes or other natural disasters.
 Rice. 1.14 |
Visible light. Visible light and ultraviolet rays are created by vibrations of electrons in atoms and ions. The region of the spectrum of visible electromagnetic radiation is very small and has boundaries determined by the properties of the human organ of vision. Visible light wavelengths range from 380 nm up to 760 nm... All colors of the rainbow correspond to different wavelengths that lie within these very narrow limits. The eye perceives radiation in a narrow range of wavelengths as monochromatic, and complex radiation, containing all wavelengths, as white light (Fig. 1.14). The wavelengths of light waves corresponding to the primary colors are given in table 7.1. As the wavelength changes, the colors smoothly transition into each other, forming many intermediate shades. The average human eye begins to distinguish a difference in color corresponding to a difference in wavelength of 2 nm.
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In order for an atom to radiate, it must receive energy from the outside. Most common heat sources light: the sun, incandescent lamps, flames, etc. The energy required for atoms to emit light can also be borrowed from non-thermal sources, for example, a discharge in a gas accompanies a glow.
The most important characteristic of visible radiation is, of course, its visibility to the human eye. The temperature of the Sun's surface, equal to about 5000 ° C, is such that the peak of the energy of the sun's rays falls precisely on the visible part of the spectrum, and the environment around us is largely transparent to this radiation. It is not surprising, therefore, that the human eye in the process of evolution was formed in such a way as to capture and recognize this particular part of the spectrum of electromagnetic waves.
The maximum sensitivity of the eye during daytime vision falls on the wavelength and corresponds to yellow-green light. In this regard, a special coating on the lenses of cameras and video cameras must transmit yellow-green light inside the equipment and reflect the rays that the eye feels weaker. Therefore, the lens shine appears to us as a mixture of red and violet colors.
Most important ways registration of electromagnetic waves in the optical range is based on the measurement of the energy flux carried by the wave. For this purpose, photoelectric phenomena (photocells, photomultipliers), photochemical phenomena (photoemulsion), thermoelectric phenomena (bolometers) are used.
Ultraviolet radiation. Ultraviolet rays include electromagnetic radiation with a wavelength from several thousand to several atomic diameters (390-10 nm). This radiation was discovered in 1802 by the physicist I. Ritter. Ultraviolet radiation is more energetic than visible light, so solar radiation in the ultraviolet range becomes hazardous to human body... Ultraviolet radiation, as you know, is generously sent to us by the Sun. But, as already mentioned, the Sun radiates the most in visible rays. In contrast, hot blue stars are a powerful source of ultraviolet radiation. It is this radiation that heats and ionizes the emitting nebulae, thanks to which we see them. But since ultraviolet radiation is easily absorbed by a gaseous medium, it hardly reaches us from distant regions of the Galaxy and the Universe if there are gas and dust barriers in the path of the rays.
 Rice. 1.15 |
Basic life experience associated with ultraviolet radiation, we acquire in the summer, when we spend a lot of time in the sun. Our hair burns out, and our skin gets sunburned and burned. Everyone knows perfectly well how it has a beneficial effect sunlight on the mood and health of a person. Ultraviolet radiation improves blood circulation, respiration, muscle activity, promotes the formation of vitamins and the treatment of certain skin diseases, activates immune mechanisms, carries a charge of vigor and good mood (Fig. 1.15).
Hard (short-wave) ultraviolet radiation, corresponding to wavelengths adjacent to the X-ray range, is detrimental to biological cells and is therefore used, in particular, in medicine for sterilization surgical instruments and medical equipment by killing all microorganisms on their surface.
 Rice. 1.16 |
All life on Earth is protected from the harmful effects of hard ultraviolet radiation by the ozone layer of the earth's atmosphere, which absorbs b O Most of the hard ultraviolet rays in the solar radiation spectrum (Fig. 1.16). If not for this natural shield, life on Earth would hardly have come to land from the waters of the World Ocean.
Ozone layer formed in the stratosphere at an altitude of 20 km up to 50 km... As a result of the rotation of the Earth highest height the ozone layer - at the equator, the smallest - at the poles. In the zone close to the Earth above the polar regions, "holes" have already formed, which have been constantly increasing over the past 15 years. As a result of the progressive destruction of the ozone layer, the intensity of ultraviolet radiation on the Earth's surface is increasing.
Up to wavelengths, ultraviolet rays can be studied by the same experimental methods as visible rays. In the wavelength range less than 180 nm significant difficulties are encountered due to the fact that these rays are absorbed by various substances, for example, glass. Therefore, in installations for the study of ultraviolet radiation, no ordinary glass rather quartz or artificial crystals. However, for such a short ultraviolet, gases are also opaque at normal pressure (for example, air). Therefore, to study such radiation, spectral installations are used, from which air is pumped out (vacuum spectrographs).
In practice, the registration of ultraviolet radiation is often performed using photoelectric radiation detectors. Registration of ultraviolet radiation with a wavelength less than 160 nm produced by special counters similar to Geiger-Muller counters.
X-ray radiation. Radiation in the wavelength range from several atomic diameters to several hundred diameters of an atomic nucleus is called X-ray. This radiation was discovered in 1895 by W. Roentgen (Roentgen named it X-rays). In 1901 W. Roentgen was the first physicist to obtain Nobel prize for the discovery of radiation named after him. This radiation can occur during braking by any obstacle, incl. metal electrode, fast electrons as a result of the conversion of the kinetic energy of these electrons into the energy of electromagnetic radiation. To obtain X-rays, special vacuum devices - X-ray tubes - are used. They consist of a vacuum glass case, in which the cathode and anode are located at a certain distance from each other, connected to a high voltage circuit. A strong electric field accelerating electrons to energy. X-rays are generated when electrons at high velocities bombard the surface of a metal anode in a vacuum. When electrons are decelerated, bremsstrahlung radiation arises in the anode material, which has a continuous spectrum. In addition, as a result of electron bombardment, the atoms of the material from which the anode is made are excited. The transition of atomic electrons to a state with a lower energy is accompanied by the emission of characteristic X-rays, the frequencies of which are determined by the anode material.
X-rays freely pass through the muscles of a person, penetrate cardboard, wood and other bodies that are opaque to light.
They cause a number of substances to glow. V. Roentgen not only discovered X-ray radiation, but also investigated its properties. He found that a low-density material is more transparent than a high-density material. X-rays penetrate the soft tissues of the body and are therefore indispensable in medical diagnostics. By placing a hand between the X-ray source and the screen, you can see a faint shadow of the hand, on which the darker shadows of the bones stand out sharply (Fig. 1.17).
Powerful flashes on the Sun are also a source of X-ray radiation (Fig. 1.19). The Earth's atmosphere is an excellent shield for X-rays.
In astronomy, X-rays are most often remembered when talking about black holes, neutron stars, and pulsars. When trapping a substance near magnetic poles stars give off a lot of energy, which is emitted in the X-ray range.
To register X-ray radiation, the same physical phenomena are used as in the study of ultraviolet radiation. Mainly, photochemical, photoelectric and luminescent methods are used.
Gamma radiation- the shortest wavelength electromagnetic radiation with wavelengths less than 0.1 nm... It is associated with nuclear processes, the phenomena of radioactive decay that occur with certain substances, both on Earth and in space.
Gamma rays are harmful to living organisms. The earth's atmosphere does not allow space gamma rays to pass through. This ensures the existence of all life on Earth. Gamma radiation is recorded by gamma-ray detectors, scintillation counters.
Thus, electromagnetic waves of various ranges have received different names and reveal themselves in completely dissimilar physical phenomena. These waves are emitted by various vibrators, recorded different methods but they have the same electromagnetic nature, propagate in a vacuum with the same speed, exhibit the phenomena of interference and diffraction. There are two main types of sources of electromagnetic radiation. In microscopic sources, charged particles jump from one energy level to another inside atoms or molecules. Emitters of this type emit gamma, X-rays, ultraviolet, visible and infrared, and in some cases even longer wavelengths. Sources of the second type can be called macroscopic. In them, free electrons of conductors perform synchronous periodic oscillations. Electrical system can have a wide variety of configurations and sizes. It should be emphasized that with a change in wavelength, qualitative differences arise: rays with a short wavelength, along with wave properties, more clearly manifest corpuscular (quantum) properties.
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Date the page was created: 2016-02-16
Topic: “Types of radiation. Sources of light. Scale of electromagnetic waves ".
Purpose: to establish common properties and differences on the topic "Electromagnetic radiation"; compare different types of radiation.
Equipment: presentation "Scale of electromagnetic waves".
During the classes.
I. Organizational moment.
II. Knowledge update.
Frontal conversation.
What kind of wave is light? What is coherence? What waves are called coherent? What is called wave interference, and under what conditions does this phenomenon occur? What is called a stroke difference? Optical path difference? How are the conditions for the formation of interference maxima and minima recorded? The use of interference in technology. What is called diffraction of light? Formulate Huygens' principle; Huygens-Fresnel principle. Name the diffraction patterns from the various obstacles. What is a diffraction grating? Where is a diffraction grating used? What is light polarization? What are polaroids used for?
III. Learning new material.
The universe is an ocean of electromagnetic radiation. People live in it, for the most part, not noticing the waves penetrating the surrounding space. Warming 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, mankind during the 20th century has mastered and put at its service its most diverse types.
We know that the length of electromagnetic waves is very different. Light makes up a tiny fraction of the wide spectrum of electromagnetic waves. When studying this small part of the spectrum, other emissions with unusual properties were discovered. It is accepted to emit low frequency radiation, radio radiation, infrared rays, visible light, ultraviolet rays, X-rays and g-radiation.
More than a hundred years, in fact, since early XIX century, the discovery of more and more waves continued. The unity of the waves was proven by Maxwell's theory. Before him, many waves were considered as phenomena of different nature... Consider the scale of electromagnetic waves, which is divided into ranges by frequency, but also by the method of radiation. There are no strict boundaries between individual ranges of electromagnetic waves. At the boundaries of the ranges, the type of wave is set according to the method of its emission, that is, an electromagnetic wave from the same frequency can in one case or another be referred to different kinds waves. For example, radiation with a wavelength of 100 microns can be referred to as radio waves or infrared waves. The exception is visible light.
Types of radiation.
type of radiation | wavelength, frequency | sources | properties | application | vacuum propagation speed |
Low frequency | 0 to 2 104 Hz from 1.5 104 to ∞ m. | alternators. | Reflection, absorption, refraction. | They are used for melting and hardening metals. | |
Radio waves | alternating current. generator of radio frequencies, stars, including the Sun, galaxies and metagalaxies. |
interference, diffraction. | To transmit information over various distances. Speech, music (broadcasting), telegraph signals (radio communication), images of various objects (radar) are transmitted. | ||
Infrared | 3 * 1011 - 3.85 * 1014 Hz. 780nm -1mm. | Radiation of molecules and atoms under thermal and electrical influences. Powerful source of infrared radiation - the Sun | Reflection, absorption, refraction, interference, diffraction. | ||
3.85 1014 - 7.89 1014 Hz | Valence electrons in atoms and molecules, changing their position in space, as well as free charges, moving at an accelerated rate. | Reflection, absorption, refraction, interference, diffraction. | The absorption of carbon dioxide by plants as a result of the process of photosynthesis and the release of oxygen contributes to the maintenance of biological life on Earth. Also, visible radiation is used when illuminating various objects. | ||
Ultraviolet | 0.2 μm to 0.38 μm 8 * 1014 - 3 * 1016 Hz | valence electrons of atoms and molecules, also accelerated moving free charges. Gas-discharge lamps with quartz tubes (quartz lamps). Solids with T> 1000 ° С, as well as luminous mercury vapors. High temperature plasma. | High chemical activity (decomposition of silver chloride, luminescence of zinc sulfide crystals), invisibly, high penetrating ability, kills microorganisms, in small doses has a beneficial effect on the human body (sunburn), but in large doses it has a negative biological effect: changes in cell development and metabolism substances, effects on the eyes. | The medicine. Luminescence center lamps. Forensic science (by discover counterfeits documents). Art history (with ultraviolet rays can be found in the pictures restoration traces not visible to the eye) | |
X-ray | 10-12-10-8 m (frequencies 3 * 1016-3-1020 Hz | Some radioactive isotopes, synchrotrons are electron storage devices. Natural sources of X-ray radiation are the Sun and other space objects. | High penetrating power. Reflection, absorption, refraction, interference, diffraction. | X-ray diffraction analysis, medicine, forensics, art history. | |
Gamma - radiation | Nuclear processes. | Reflection, absorption, refraction, interference, diffraction. | In the study of nuclear processes, in defectoscopy. |
Similarities and differences.
General properties and characteristics of electromagnetic waves.
Properties | Specifications |
Spreading through space over time | The speed of electromagnetic waves in a vacuum is constant and equal to approximately 300,000 km / s |
All waves are absorbed by matter | Various absorption coefficients |
All waves at the interface between the two media are partially reflected and partially refracted. | The laws of reflection and refraction. Reflection coefficients for different media and different waves. |
All electromagnetic radiation exhibits the properties of waves: they fold, bend around obstacles. Several waves can simultaneously exist in one area of space | Superposition principle. For coherent sources, the rules for determining the maximums. Huygens-Fresnel principle. Waves do not interact with each other |
Complex electromagnetic waves, when interacting with matter, are decomposed into a spectrum - dispersion. | Dependence of the refractive index of the medium on the wave frequency. The wave velocity in a substance depends on the refractive index of the medium v = c / n |
Waves of different intensities | Radiation flux density |
As the wavelength decreases quantitative differences in wavelengths lead to significant qualitative differences. Radiation of different wavelengths are very different from each other in their absorption by matter. Shortwave radiation is weakly absorbed. Substances that are opaque to waves in the optical range are transparent to these radiations. The reflectance of electromagnetic waves also depends on the wavelength. But the main difference between longwave and shortwave radiation is that shortwave radiation exhibits particle properties.
1 Low frequency radiation
Low-frequency radiation occurs in the frequency range from 0 to 2 104 Hz. This radiation corresponds to a wavelength of 1.5 104 to ∞ m. The radiation of such relatively low frequencies can be neglected. The source of low frequency radiation is alternating current generators. They are used for melting and hardening metals.
2 Radio waves
Radio waves occupy the frequency range 2 * 104-109 Hz. They correspond to a wavelength of 0.3-1.5 * 104 m. The source of radio waves, as well as low-frequency radiation, is alternating current. The source is also a radio frequency generator, stars, including the Sun, galaxies and metagalaxies. The indicators are a Hertz vibrator, an oscillatory circuit.
The high frequency of radio waves, in comparison with low-frequency radiation, leads to a noticeable emission of radio waves into space. This allows them to be used to transmit information over different distances. Speech, music (broadcasting), telegraph signals (radio communication), images of various objects (radar) are transmitted. Radio waves are used to study the structure of matter and the properties of the medium in which they propagate. The study of radio emission from space objects is the subject of radio astronomy. In radio meteorology, processes are studied based on the characteristics of the received waves.
3 Infrared (IR)
Infrared radiation occupies the frequency range 3 * 1011 - 3.85 * 1014 Hz. They correspond to a wavelength of 780nm –1mm. Infrared radiation was discovered in 1800 by astronomer William Herschl. Studying the rise in temperature of a thermometer heated by visible light, Herschel found that the thermometer warms up most outside the visible light region (behind 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 paints and varnishes (infrared heating), for signaling in poor visibility, makes it possible to use optical devices that allow you to see in the dark, as well as with remote control. Infrared beams are used to aim projectiles and missiles at a target, to detect a camouflaged enemy. These rays make it possible to determine the difference in temperatures of individual parts of the surface of planets, the structural features of the molecules of matter (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 forensic science when detecting fakes. When exposed to humans, it causes an increase in the temperature of the human body.
Visible radiation (light)
Visible radiation is the only range of electromagnetic waves perceived by the human eye. Light waves occupy a rather narrow range: 380-780 nm (ν = 3.85 1014-7.89 1014 Hz). The source of visible radiation are valence electrons in atoms and molecules, which change their position in space, as well as free charges moving at an accelerated rate. This part of the spectrum gives a person the maximum information about the world around him. In terms of its physical properties, it is similar to other ranges of the spectrum, being only a small part of the spectrum of electromagnetic waves. Radiation, which has different wavelengths (frequencies) in the range of visible radiation, has different physiological effects on the retina of the human eye, causing a psychological sensation of light. Color is not a property of an electromagnetic light wave in itself, but a manifestation of the electrochemical action of the human physiological system: eyes, nerves, brain. There are approximately seven primary colors distinguishable by the human eye in the visible range (in ascending order of radiation frequency): red, orange, yellow, green, cyan, blue, violet. Memorizing the sequence of the primary colors of the spectrum is facilitated by the 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 affect the course of chemical reactions in plants (photosynthesis) and in the organisms of animals and humans. 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 of oxygen release contributes to the maintenance of biological life on Earth. Also, visible radiation is 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.
5. Ultraviolet radiation
Ultraviolet radiation, electromagnetic radiation invisible to the eye, occupying the spectral region between visible and X-ray radiation within the wavelength range of 10 - 380 nm (ν = 8 * 1014-3 * 1016 Hz). Ultraviolet radiation was discovered in 1801 by the German scientist Johann Ritter. While studying the blackening of silver chloride by 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 radiation. The source of ultraviolet radiation is the valence electrons of atoms and molecules, and also accelerated moving free charges. The radiation of solids heated to temperatures of - 3000 K contains a noticeable fraction of ultraviolet radiation of the continuous spectrum, 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 are the Sun, stars, nebulae and other space objects. However, only the long-wavelength part of their radiation (λ> 290 nm) reaches the earth's surface. To register ultraviolet radiation at λ = 230 nm, ordinary photographic materials are used; in the shorter wavelength region, special low-gelatin photographic layers are sensitive to it. Photoelectric detectors are used that use the ability of ultraviolet radiation to cause ionization and photoelectric effect: photodiodes, ionization chambers, photon counters, photomultipliers.
In small doses, ultraviolet radiation has a beneficial, health-improving effect on humans, 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 UV radiation weakens the body's immune system, contributing to the development of certain diseases. Ultraviolet radiation also has a bactericidal effect: pathogenic bacteria die under the action of this radiation.
Ultraviolet radiation is used in fluorescent lamps, in forensic science (forgeries are detected from photographs), in art history (with the help of ultraviolet rays, traces of restoration that are not visible to the eye can be found in paintings). Window glass practically does not transmit ultraviolet radiation, since it is absorbed by iron oxide, which is part of the glass. For this reason, even on a hot sunny day, you cannot sunbathe in the room with the window closed. The human eye cannot see ultraviolet radiation because the cornea and the eye lens absorb ultraviolet light. Some animals see ultraviolet radiation. For example, a pigeon is guided by the sun even in cloudy weather.
6. X-ray radiation
X-ray radiation is electromagnetic ionizing radiation that occupies the spectral region between gamma and ultraviolet radiation in the range of wavelengths from 10-12-10-8 m (frequencies 3 * 1016-3-1020 Hz). X-rays were discovered in 1895 by a German physicist. The most common X-ray source is an X-ray tube in which electrons accelerated by an electric zero bombard a metal anode. X-rays can be produced by bombarding a target with high-energy ions. Some radioactive isotopes and electron storage synchrotrons can also serve as X-ray sources. Natural sources of X-ray radiation are the Sun and other space objects.
X-ray images of objects 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, microchannel plates. Due to its high penetrating power, X-ray radiation is used in X-ray structural analysis (study of the crystal lattice structure), in the study of the structure of molecules, in 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 painting hidden under a layer of late painting), in astronomy (when studying X-ray sources), forensics. A large dose of X-ray radiation leads to burns and changes in the structure of the human blood. The creation of X-ray detectors and their placement at space stations made it possible to detect X-rays from hundreds of stars, as well as the shells of supernovae and entire galaxies.
7. Gamma radiation (γ - rays)
Gamma radiation - short-wave electromagnetic radiation occupying the entire frequency range ν> З * 1020Hz, which corresponds to wavelengths λ<10-12 м. Гамма излучение было открыто французским ученым Полем Вилларом в 1900 году. Изучая излучение радия в сильном магнитном поле, Виллар обнаружил коротковолновое электромагнитное излучение, не отклоняющееся, как и свет, магнитным полем. Оно было названо Iгамма излучением. Гамма излучение связано с ядерными процессами, явлениями радиоактивного распада, происходящими с некоторыми веществами, как на Земле, так и в космосе. Гамма излучение можно регистрировать с помощью ионизационных и пузырьковых камер, а также с помощью специальных фотоэмульсий. Используются при исследовании ядерных процессов, в дефектоскопии. Гамма излучение отрицательно воздействует на человека.
IV. Consolidation of the studied material.
Low frequency radiation, radio waves, infrared radiation, visible radiation, ultraviolet radiation, X-ray radiation, γ-radiation are various types of electromagnetic radiation.
If you mentally decompose these types in increasing frequency or decreasing wavelength, you get a wide continuous spectrum - the scale of electromagnetic radiation (the teacher shows the scale). The division of electromagnetic radiation into ranges is conditional. There is no clear border between the regions. The names of the regions have developed historically, they only serve as a convenient means of classifying radiation sources.
All ranges of the electromagnetic emission scale have common properties:
- The physical nature of all radiations is the same. All radiations propagate in a vacuum at the same speed, equal to 3 * 108 m / s. All radiations exhibit common wave properties (reflection, refraction, interference, diffraction, polarization).
A). Complete tasks to determine the type of radiation and its physical nature.
1. Do burning wood emit electromagnetic waves? Non-burning? (They emit. Burning - infrared and visible rays, and non-burning - infrared).
2. What explains the white color of snow, black soot, green leaves, red paper? (Snow reflects all waves, soot absorbs everything, leaves reflect green, paper - red).
3. What role does the atmosphere play in life on Earth? (UV protection).
4. Why does dark glass protect the welder's eyes? (Glass does not transmit ultraviolet light, but dark glass and the bright visible radiation of the flame that occurs during welding).
5. When satellites or spaceships pass through the ionized layers of the atmosphere, they become sources of X-ray radiation. Why? (In the atmosphere, fast moving electrons hit the walls of moving objects and X-rays are generated.)
6.What is microwave radiation and where is it used? (Ultra-high frequency radiation, microwave ovens).
B). Verification test.
1. Infrared radiation has a wavelength:
A. Less than 4 * 10-7 m. B. More than 7.6 * 10-7 m C. Less than 10 -8 m
2. Ultraviolet radiation:
A. Occurs with a sharp deceleration of fast electrons.
B. It is intensely emitted by bodies heated to a high temperature.
B. Emitted by any heated body.
3. What is the visible wavelength range?
A. 4 * 10-7- 7.5 * 10-7 m. B. 4 * 10-7- 7.5 * 10-7 cm. C. 4 * 10-7- 7.5 * 10-7 mm ...
4. The highest passing capacity has:
A. Visible radiation B. Ultraviolet radiation C. X-ray radiation
5. An image of an object in the dark is obtained using:
A. Ultraviolet radiation. B. X-ray radiation.
B. Infrared radiation.
6. Who first discovered γ-radiation?
A. Roentgen B. Villard W. Herschel
7. How fast does infrared radiation travel?
A. More than 3 * 108 m / s B. Less than 3 * 108 m / s B. 3 * 108 m / s
8. X-ray radiation:
A. Occurs with a sharp deceleration of fast electrons
B. Emitted by solids heated to high temperatures
B. Emitted by any heated body
9. What kind of radiation is used in medicine?
Infrared radiation Ultraviolet radiation Visible radiation X-ray radiation
A. 1,2,4 B. 1,3 V. All emissions
10. Ordinary glass practically does not transmit:
A. Visible radiation. B. Ultraviolet radiation. C. Infrared radiation Correct answers: 1 (B); 2 (B); 3 (A); 4 (B); 5 (B); 6 (B); 7 (B); 8 (A); 9 (A); 10 (B).
Grading scale: 5 - 9-10 tasks; 4 - 7-8 tasks; 3 - 5-6 tasks.
IV. Lesson summary.
V. Homework: §80.86.