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Sodikova Shokhida, teacher, National University of Uzbekistan, named after Mirzo Ulugbek, Taskent, Uzbekistan E-mail: [email protected]
METHODS FOR DEVELOPING AND GIVING SPECIAL COURSES ON "LASERS AND THEIR PRACTICAL APPLICATIONS"
Abstract: The article discusses the experience of developing and giving a special course on "Lasers and their practical applications" in academic lyceums and colleges for in-depth study of physics.
Keywords: Quantum of light, absorption of light, laser, stimulated emission, stimulated transition, monochromatic light, radiation, optical quantum generator.
To ensure a better continuity between academic lyceums and university forms of education, in the academic lyceums it is recommended to practice giving lectures, seminars, workshops on special subjects, especially related to the development of new techniques and technologies along with the lessons.
Physics teacher, who holds university degree, having the physical and mathematical basic education, has the necessary scientific and methodical preparation for the development and implementation of the special courses on current trends in modern physics at academic lyceum. He acquires these skills in a modules of methodical disciplines, teacher training, preparing projects and dissertations. The selection process of modules for specialized courses in lyceum involves the defining their content and their implementation into educational curriculum, hence some methodical issues get their solution.
First of all, it should be noted that the main content of the course of physics of academic lyceum, is focused on fundamental laws and principles of physics, and for this reason, the content is, to some extent, conservative. That is why the content of the basic physics textbooks is changing slowly over the years and there is a problem of selecting the issues and questions of modern and applied physics that contributes to the value of presenting special courses. These issues include microelectronics, nanotechnology, lasers and their practical applications, semiconductors and their use, optical fiber and its practical significance, the introduction of superconductivity in physics and others.
It is important to point out the major methodological problems to be solved for the development and realization of special discipline such as "Lasers and their practical applications" in academic lyceums.
1. A complex and abstract theoretical and experimental data of modern physics should to be fully adapted to the cognitive abilities of students.
2. It is necessary to provide substantive, methodological, terminological, symbolic, graphical and symbolic continuity, as well as intra-and interdisciplinary relationship of special course with basic course in physics, mathematics and others.
3. Special courses should be focused on the implementation of the principles ofpolytechnics. They should reveal wide technical application of various industrial achievements of physics, the physical basis of different areas of technology and production, the most important principles of instruments and devices, clarify technical and economical problems of the national economy. Reflection of the achievements and contributions of scientists of Uzbekistan in the development of specific branches of physics and technology has an important educational and vocational guidance significance.
4. Highly informative, pedagogic and psychological properties of the physical, in particular, demonstrational experiment create the ground for realization of the tasks listed in paragraph 3, and give a chance to achieve a higher cognitive level for the trainees. In this regard, in the implementation of special disciplines, special attention should be given to the widespread use ofvarious types of visual aids: educational films, educational posters, slides, models and real physical experiment.
Below the experience in the development and implementation of a special course "Lasers and their practical applications "for the 1st - 2nd year students academic lyceums of Uzbekistan with the participation of 3rd - 4th - year university Physics Students is described.
METHODS FOR DEVELOPING AND GIVING SPECIAL COURSES ON "LASERS AND THEIR PRACTICAL APPLICATIONS"
The program of lasers and their practical application
1. Patterns and types of radiation
Physical laws of radiation. Forced and spontaneous radiation. Energy surfaces and their formation. The design and principle of operation of lasers. Features of laser radiation. I - The first colloquium to check understanding of the chapter [1, 17-20].
2. Types and construction of lasers
Solid-state lasers. Gas Lasers. Ion lasers. Chemical lasers. Semiconductor lasers. Research works of scientists-physicists of Uzbekistan. II - The second colloquium to check understanding of the chapter [2, 164-198].
3. Applications of lasers
Optical connection. Holography. Application of lasers in medicine. Laser processing of materials. Application of lasers in agriculture. Control of individual processes using laser beams. III - The third colloquium to check understanding of the chapter [3, 83-98; 4, 308-315].
4. Demonstrational experiments with the help of laser beams on optics physics
Demonstrational experiments on the division of geometric optics. Demonstrational experiments on interference oflight. Demonstrational experiments on diffraction of light. Demonstrational experiments on the polarization of light. Features of laser beams and experiments on the application. Glossary [5, 59-78].
As an example, let's take the scenario technology of the problematic study "Optical connection". The lecture can begin with the formulation of problem questions.
Can I talk on a light beam? With the invention of the laser, man has at his disposal a source of intense coherent electromagnetic radiation in the optical frequency range - up to 1015 Hz. In this connection, naturally, the question arose about extending the principles of radio communication to the optical range. Arose and began to develop laser communication - a connection carried out with the help of modulated laser radiation. Usually a semiconductor laser or a helium-neon laser is used. The laser radiation is modulated by sound vibrations in the modulator and through the targeting device is directed to the subscriber at the receiving end of the line. There, the laser beam enters the receiver, and then into the demodulator, which emits sound vibrations. These vibrations are amplified and fall into the sound reproduction device.
The laser beam is transmitted not only by telephone conversations, it can also transmit a television program.
What is interesting and promising for laser communication? As is known, for the transmission of speech, music, images, it is necessary to modulate the electromagnetic wave accordingly, for example, it is necessary to change its amplitude according to a certain law. The frequencies characterizing the rapidity of changes in the amplitude of the wave must be at least ten to one hundred times lower than the frequency of the wave itself. The modulation frequencies occupy a certain band. Its width is the greater, the larger the amount of information transmitted per unit of time. Due to the high directivity of the laser beam, it is possible to realize several communication channels on the same carrier, choosing different directions in space each time. The radiation direction can significantly reduce the power consumption of the transmitter power. In addition, the danger of unwanted interception of transmitted information decreases. Noting the advantages of laser communication, we must at the same time point out one of its vulnerabilities. This is the influence of the atmosphere on the laser beam. Fog, rain, snowfall, dust, cloudiness - all this, as you know, sharply limits visibility, which means it tears off the optical connection.
What are the difficulties of implementing laser communications in terrestrial conditions? The main obstacle to the creation of reliable lines of laser connections in terrestrial conditions is the effect of the atmosphere on the laser beam. This impact can disrupt not only a long-range, but also a relatively close connection, for example, a laser telephone connection between two objects and the city borders. The effect of the atmosphere on the laser beam is in two ways. First, there is a gradual decrease in the intensity of the beam due to absorption and scattering of light by gases, water vapor, aerosols. Secondly, the distortions of the wave front accumulating along the propagation path occur, mainly due to the turbulence of the atmosphere. The absorption of light in the atmosphere depends very strongly on the wavelength. To combat distortions of the wave front, they tend to increase the radiation directivity, awaiting favorable weather conditions. All these measures do not allow, but, increase the length of the earth's communication lines more than a few tens ofkilometers. The main thing is that there is still a dependence of quality and the very fact ofhaving a connection from weather conditions.
It is expected, that the situation can change qualitatively when using the methods of adaptive optics in laser communication lines, allowing the necessary correction ofthe wave front of radiation.
How does light propagate in dielectric fibers? To get rid of the influence of the atmosphere completely, you can use special light guides. Light guides in the form of thin dielectric fibers were widely used, in connection with which a new direction in modern optics - fiber optics - arose.
The light beam introduced into the fiber is retained inside it due to the phenomenon of total internal reflection of light from the side surface of the fiber. Light runs through the fiber, obediently following all its bends. For
a more reliable retention of light within the fiber, special fibers are used, called gradient ones. In them, the refractive index is maximal near the fiber axis and gradually decreases towards the side surface.
Thus, the basis ofthe organization of problem - based learning is the principle of the student's learning - cognitive activity, i. e. the principle of "open" to him scientific facts, phenomena, laws, methods of research and ways to apply knowledge in practice.
The direct participation of students preparing for teaching activities in the development and teaching of a special course was an important incentive for their professional growth and the development of their research skills in the field of methodology.
References:
1. Lendel B. Lasers.- Moscow: Mir,- 1964.- 200 p.
2. Kachmarek F. Introduction to the physics of lasers.- Moscow: Mir,- 1981.- 532 p.
3. Sobolev N. Lasers and their future.- Moscow: Atomizdat,- 1968.- 190 p.
4. Karasik V. E., Orlov V. M. Laser vision systems.- Moscow: MGTU,- 2001.- 350 p.
5. Mansurov A. N. Lasers and their application in the teaching of physics.- Moscow: Enlightenment,- 1984.- 88 p.
