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MOST IMPORTANT SCIENTIFIC DISCOVERIES
Electromagnetic theory of light. History and essence of scientific discovery
Directory / The most important scientific discoveries "In my time Newton was convinced that light consists of the smallest particles, the speed of movement of which is almost infinite, - says T. Regge in the background of the issue. - His contemporary Huygens, on the contrary, was a supporter of the wave mechanism of light propagation, similar to the process of sound propagation in air or in any material medium. The indisputable authority of Newton did not allow the recognition of Huygens' hypothesis. In 1700, Jung, Fresnel and some other scientists began to study optical phenomena that were incomprehensible from the point of view of Newton's ideas. These phenomena directly indicated the wave nature of light. Paradoxically, among these phenomena were Newton's rings, well known to photographers and arising when a transparencies are placed between glass plates. The bright coloration of some insects also arises as a result of complex processes of light wave interference occurring in thin layers of liquid crystals located on the surface of the body of insects. However, despite the obvious successes of the wave mechanical theory of light in the second half of the XNUMXth century, it was questioned for two reasons. One is experiences Faradaywho discovered the effect of a magnetic field on light. The other is research on the connection between electrical and magnetic phenomena, which was carried out by Maxwell. “The discovery of the electromagnetic nature of light is a magnificent illustration of the dialectics of the development of content and form,” writes P.S. Kudryavtsev. “The new content - electromagnetic waves - was expressed in the old form of Cartesian vortices. The discrepancy between the new content that appeared as a result of the development of electromagnetism, not only the old form of the theory of long-range action, but also the mechanical theory of the ether was already felt by Faraday, who was looking for a new form to express this content. He saw such a form in the lines of force, which should be considered not statically, but dynamically. The development of this idea is devoted to his works "Thoughts on ray vibrations" (1846) and "On the physical lines of magnetic force" (1851). Faraday's discovery in 1845 of the connection between magnetism and light was a new content in the theory of light and at the same time once again pointed to the strict transverse nature of light vibrations. All this did not fit well into the old form of mechanical ether." Faraday puts forward the idea of lines of force in which transverse oscillations occur. .) are taken as the basis of radiation and the phenomena associated with it, occur in the lines of forces connecting the particles, and consequently, the masses of matter into one whole. This idea, if admitted, will free us from the ether, which, from another point of view, is the medium in which these oscillations take place. The scientist points out that the oscillations occurring in the lines of forces are not a mechanical process, but a new form of movement, "a certain higher type of oscillation." Such fluctuations are transverse and therefore can "explain the wonderful diverse phenomena of polarization." They are not like longitudinal sound waves in liquids and gases. His theory, he says, "tries to eliminate the ether, but not the vibrations." These magnetic oscillations propagate at a finite speed: "... The appearance of a change at one end of the force suggests a subsequent change at the other. The propagation of light, and therefore, probably, of all radiant actions, takes time, and in order for the oscillation of the lines of force to explain the phenomena of radiation, it is necessary that such an oscillation also take time ". The search for a new form led the scientist to the formation of an important idea of transverse magnetic oscillations, which, like light, propagate at a finite speed. But this is the central idea of the electromagnetic theory of light - an idea that arose as early as 1832. Maxwell noted in a note to W. Bragg: "The electromagnetic theory of light proposed by him (Faraday) in "Thoughts on Radial Vibrations" (May, 1846) or "Experimental Investigations" is essentially the same that I began to develop in this article ("Dynamical Field Theory" (May, 1865), except that in 1846 there were no data for calculating the speed of propagation." Such recognition, however, does not belittle the merit in the study of the electromagnetic field by James Maxwell. James Maxwell (1831–1879) was born in Edinburgh. Shortly after the birth of the boy, his parents took him to their estate Glenlar. At first, teachers were invited to the house. Then it was decided to send James to a new school, which bore the loud name of the Edinburgh Academy. Maxwell was one of the first to graduate from the academy, and the doors of Edinburgh University opened before him. As a student, Maxwell carried out serious research on the theory of elasticity, which was highly appreciated by specialists. And now he was faced with the question of the prospect of his further studies at Cambridge. The volume of Maxwell's knowledge, the power of his intellect and independence of thought allowed him to achieve a high place in his release. He took second place. The young bachelor was left at Cambridge - Trinity College as a teacher. However, he was concerned about scientific problems. In addition to his old passion - geometry and the problem of colors, which he began to study as early as 1852, Maxwell became interested in electricity. On February 20, 1854, Maxwell informs Thomson of his intention to "attack electricity". The result of the "attack" is the essay "On Faraday's Lines of Force" - the first of Maxwell's three main works devoted to the study of the electromagnetic field. The word "field" first appeared in that same letter to Thomson, but Maxwell does not use it in this or in a subsequent work on lines of force. This concept reappears only in 1864 in the work "Dynamical Theory of the Electromagnetic Field". He publishes two major works on the electromagnetic field theory he created: "On Physical Lines of Force" (1861-1862) and "Dynamical Theory of the Electromagnetic Field" (1864-1865). For ten years, Maxwell has grown into a prominent scientist, the creator of the fundamental theory of electromagnetic phenomena, which, along with mechanics, thermodynamics and statistical physics, has become one of the foundations of classical theoretical physics. "Treatise on Electricity and Magnetism" - the main work of Maxwell and the pinnacle of his scientific work. In it, he summed up the results of many years of work on electromagnetism, which began as early as the beginning of 1854. The preface to the "Treatise" is dated February 1, 1873. Nineteen years Maxwell worked on his fundamental work! Maxwell's research led him to the conclusion that electromagnetic waves must exist in nature, the propagation speed of which in airless space is equal to the speed of light - 300 kilometers per second. Having arisen, the electromagnetic field propagates in space at the speed of light, occupying a larger and larger volume. Maxwell argued that the waves of light are of the same nature as the waves that arise around a wire in which there is an alternating electric current. They differ from each other only in length. Very short wavelengths is visible light. "Maxwell's assumption that changes in the electric field entail the emergence of a magnetic induction flux was the next step forward," writes A.A. Korobko-Stefanov. "Thus, the resulting alternating electric field around the magnetic field, in turn, creates an alternating a magnetic field embracing an electric field, which again excites an electric field, etc. Rapidly changing electric and magnetic fields propagating at the speed of light form an electromagnetic field. An electromagnetic field propagates in space from point to point, creating electromagnetic waves. The electromagnetic field at each point is characterized by the strength of the electric and magnetic fields. The intensity of the electric and magnetic fields are vector quantities, since they are characterized not only by magnitude, but also by direction. The field strength vectors are mutually perpendicular and perpendicular to the direction of propagation. Therefore, the electromagnetic wave is transverse. It followed from Maxwell's theory that electromagnetic waves arise if changes in the strength of the electric and magnetic fields occur very quickly. The validity of Maxwell's ideas was empirically proved by Heinrich Hertz. In the eighties of the nineteenth century, Hertz began to study electromagnetic phenomena, working in an auditorium 14 meters long and 12 meters wide. He found that if the distance of the receiver from the vibrator is less than one meter, then the nature of the distribution of the electric force is similar to the dipole field and decreases inversely as the cube of the distance. However, at distances exceeding 3 meters, the field decreases much more slowly and is not the same in different directions. In the direction of the axis of the vibrator, the action decreases much faster than in the direction perpendicular to the axis, and is hardly noticeable at a distance of 4 meters, while in the perpendicular direction it reaches distances greater than 12 meters. This result contradicts all laws of the long-range theory. Hertz continued research in the wave zone of his vibrator, the field of which he later calculated theoretically. In a number of subsequent works, Hertz irrefutably proved the existence of electromagnetic waves propagating at a finite speed. "The results of my experiments on fast electrical oscillations," Hertz wrote in his eighth article in 1888, "showed me that Maxwell's theory has an advantage over all other theories of electrodynamics." The field in this wave zone at different moments of time was depicted by Hertz using a picture of lines of force. These drawings by Hertz were included in all electricity textbooks. Hertz's calculations formed the basis of the theory of antenna radiation and the classical theory of radiation of atoms and molecules. Thus, in the course of his research, Hertz finally and unconditionally switched to Maxwell's point of view, gave a convenient form to his equations, supplemented Maxwell's theory with the theory of electromagnetic radiation. Hertz obtained experimentally the electromagnetic waves predicted by Maxwell's theory and showed their identity with the waves of light. In 1889, Hertz read a report "On the Relationship Between Light and Electricity" at the 62nd Congress of German Naturalists and Physicians. Here he sums up his experiments in the following words: "All these experiments are very simple in principle, but, nevertheless, they entail the most important consequences. They destroy any theory that considers that electric forces jump space instantly. They mean a brilliant the victory of Maxwell's theory ... How unlikely her view of the essence of light seemed earlier, it is now so difficult not to share this view. In 1890, Hertz published two articles: "On the basic equations of electrodynamics in bodies at rest" and "On the basic equations of electrodynamics for moving bodies." These articles contained research on the propagation of "electric force rays" and, in essence, gave that canonical exposition of Maxwell's theory of the electric field, which has since been included in textbooks. Author: Samin D.K.
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