Hertz's experiments on electromagnetic waves message. Hertz's experiments

2. Describe Hertz’s experiment in detecting electromagnetic waves

3. Explain the results of Hertz’s experiment using Maxwell’s theory. Why is an electromagnetic wave transverse?

Because the directions of the magnetic field induction and intensity vectors electric field perpendicular to each other and to the direction of the wave.

4. Why does the radiation of electromagnetic waves occur with the accelerated movement of electric charges? How does the electric field strength in an emitted electromagnetic wave depend on the acceleration of the emitting charged particle?

5. How does the energy density of the electromagnetic field depend on the electric field strength?

Electromagnetic waves (EMW) are an electromagnetic field that propagates with at different speeds depending on the environment. The speed of propagation of such waves in vacuum space is equal to the speed of light. Electromagnetic waves can be reflected, refracted, subject to diffraction, interference, dispersion, etc.

Electromagnetic waves

An electric charge is set into oscillation along a line like spring pendulum at a very high speed. At this time, the electric field around the charge begins to change with a periodicity equal to the periodicity of oscillations of this charge. A non-constant electric field will give rise to a non-constant magnetic field. It will in due time generate an electric field varying at certain periods at a greater distance from the electric charge. The described process will occur more than once.

As a result, a whole system of non-constant electric and magnetic fields appears around the electric charge. They cordon off increasingly large areas of space around up to certain limit. This is an electromagnetic wave that is distributed from the charge in all directions. At each individual point in space, both fields change with different time periods. Field oscillations quickly reach a point located close to the charge. To a more distant point - later.

A necessary condition for the appearance of electromagnetic waves is the acceleration of electric charge. Its speed should change over time. The higher the acceleration of a moving charge, the stronger the electromagnetic waves emit.

Electromagnetic waves are emitted transversely - the electric field intensity vector occupies a position at 90 degrees to the magnetic field induction vector. Both of these vectors go at 90 degrees to the direction of the electromagnetic wave.

About the fact of availability electromagnetic waves Michael Faraday wrote in 1832, but the theory of electromagnetic waves was developed by James Maxwell in 1865. Having discovered that the speed of propagation of electromagnetic waves was equal to the speed of light known at that time, Maxwell made a reasonable assumption that light is nothing more than an electromagnetic wave.

However, it was possible to experimentally confirm the correctness of Maxwell’s theory only in 1888. One German physicist did not believe Maxwell and decided to refute his theory. However, after experimental studies, he only confirmed their existence and experimentally proved that electromagnetic waves really exist. Thanks to his work on the behavior of electromagnetic waves, he became famous throughout the world. His name was Heinrich Rudolf Hertz.

Hertz's experiments

High-frequency oscillations, which significantly exceed the frequency of the current in our sockets, can be produced using an inductor and a capacitor. The oscillation frequency will increase as the inductance and capacitance of the circuit decrease.

True, not all oscillatory circuits allow the extraction of waves that can be easily detected. In closed oscillatory circuits, energy is exchanged between capacitance and inductance, and the amount of energy that goes into environment too little to create electromagnetic waves.

How to increase the intensity of electromagnetic waves so that it becomes possible to detect them? To do this, you need to increase the distance between the capacitor plates. And the covers themselves should be reduced in size. Then increase it again and decrease it again. Until we come to a straight wire, just a little unusual. It has one feature - zero current at the ends and maximum in the middle. It's called open oscillatory circuit.

Through experimentation, Heinrich Hertz came up with an open oscillatory circuit, which he called a “vibrator.” It consisted of two conductor balls with a diameter of about 15 centimeters, mounted on the ends of a wire rod cut in half. In the middle, on the two halves of the rod, there are also two smaller balls. Both rods were connected to an induction coil, which produced high voltage.

This is how the Hertz device works. The induction coil creates a very high voltage and delivers opposite charges to the balls. After a certain period of time, an electric spark appears in the gap between the rods. It reduces air resistance between the rods and appears in the circuit damped oscillations high frequency. And, since our vibrator is an open oscillatory circuit, it begins to emit electromagnetic waves.

To detect the waves, a device is used that Hertz called a “resonator”. It is an open ring or rectangle. Two balls were installed at the ends of the resonator. In his experiments, Hertz tried to find the correct dimensions for the resonator, its position relative to the vibrator, and the distance between them. With the correct size, position and distance between the vibrator and the resonator, resonance occurred. In this case, the electromagnetic waves that the circuit emits produce an electrical spark in the detector.

Using the tools at hand, namely a sheet of iron and a prism made of asphalt, this incredibly resourceful experimenter was able to calculate the lengths of the waves being propagated, as well as the speed at which they travel. He also discovered that these waves behave exactly the same as others, which means they can be reflected, refracted, diffraction and interference.

Application

Hertz's research attracted the attention of physicists around the world. Thoughts about where electromagnetic waves could be used arose among scientists here and there.

Radio communication is a method of transmitting data by emitting electromagnetic waves with a frequency from 3×104 to 3×1011 Hertz.

In our country, the founder of the radio transmission of electromagnetic waves was Alexander Popov. First he repeated Hertz's experiments, and then he reproduced Lodge's experiments and built his own modification of Lodge's first radio receiver in history. The main difference between Popov's receiver is that he created a device with feedback.

Lodge's receiver used a glass tube with metal filings that changed their conductivity under the influence of an electromagnetic wave. However, it worked only once, and in order to record another signal, the tube had to be shaken.

In Popov’s device, the wave reaching the tube turned on a relay, which triggered the bell and set the device into operation, striking the tube with a hammer. It shook the metal filings and thereby made it possible to record a new signal.

Radiotelephone communication– transmission of voice messages via electromagnetic waves.

In 1906, the triode was invented and 7 years later the first tube oscillator was created. continuous oscillations. Thanks to these inventions, it became possible to transmit short and longer electromagnetic waves pulses, as well as the invention of telegraphs and radiotelephones.

Sound vibrations that are transmitted to the telephone handset are converted into an electric charge of the same form through a microphone. However, a sound wave is always a low-frequency wave; in order for electromagnetic waves to be emitted strongly enough, it must have a high vibration frequency. The inventors solved this problem very simply.

The high-frequency waves that are produced by the generator are used for transmission, and the low-frequency sound waves are used to modulate the high-frequency waves. In other words, sound waves change some characteristics of high-frequency waves.

So, these were the first devices designed on the principles electromagnetic radiation.

And here is where electromagnetic waves can be found now:

• Mobile communications, Wi-Fi, television, remote controls, microwave ovens, radars, etc.
• IR night vision devices.
• Counterfeit money detectors.
• X-ray machines, medicine.
• Gamma-ray telescopes in space observatories.

As you can see, Maxwell’s brilliant mind and Hertz’s extraordinary ingenuity and efficiency gave rise to a whole range of devices and household items that are an integral part of our lives today. Electromagnetic waves are divided by frequency range, although very arbitrarily.

In the following table you can see the classification of electromagnetic radiation by frequency range.

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Ministry of Higher and Secondary Education of the Republic of Uzbekistan

National University of the Republic of Uzbekistan named after. Mirzo Ulugbek

Faculty of Physics

Report

Discipline: "Optics"

On the topic: “Experiments of Heinrich Hertz”

Prepared by:

2nd year student

Nebesny Andrey Anatolievich

Supervisor:

Doctor of Physical and Mathematical Sciences prof.

Valiev Uygun Vakhidovich

Tashkent 2015

Introduction

1. Statement of the problem

2. Interesting phenomenon

3. Hertz vibrator

4. Ruhmkorff coil

5. Experimenting with a vibrator

Afterword

Literature

Introduction

Heinrich Hertz was born in 1857 in Hamburg (Germany) into the family of a lawyer. Since childhood, he had an excellent memory and excellent abilities in drawing, languages, technical creativity and showed interest in exact sciences. In 1880, at the age of 23, he graduated from the University of Berlin, brilliantly defending his doctoral dissertation on theoretical electrodynamics. Scientific supervisor Hertz was the famous European physicist G. Helmholtz, for whom Hertz worked as an assistant for the next three years.

Helmholtz, who dealt with many problems in physics, developed his own version of theoretical electrodynamics. His theory competed with the previously presented theories of W. Weber and J. C. Maxwell. These were the main three theories of electromagnetism at that time. However, experimental confirmation was required.

1. Statement of the problem

In 1879, the Berlin Academy of Sciences, on the initiative of Helmholtz, put forward a competitive task: “To establish experimentally whether there is a connection between electrodynamic forces and dielectric polarization" The solution to this problem, i.e. experimental confirmation was supposed to answer which of the theories is correct. Helmholtz suggested that Hertz take on this task. Hertz tried to solve the problem using electrical oscillations that occur during the discharge of capacitors and inductors. However, he soon encountered a problem - much higher-frequency oscillations were required than they were able to obtain at that time.

Oscillations of high frequency, significantly exceeding the frequency industrial current(50 Hz), can be obtained using an oscillating circuit. The oscillation frequency u=1/v(LC) will be greater, the lower the inductance and capacitance of the circuit.

A simple calculation shows that to create the frequencies that Hertz subsequently managed to obtain (500 MHz), a capacitor with a capacity of 2 nF and an inductor of 2 nH are needed. However, the industrial progress of that time had not yet reached the possibility of creating such small capacitances and inductances.

2. Interesting phenomenon

Having failed to solve this problem, he retained the hope of finding the answer. Since then, everything related to electrical vibrations has invariably interested him.

Later, in the fall of 1886, while debugging the lecture equipment, namely checking induction coils With the spark gap between the metal balls at the ends of the windings finely adjusted using a micrometric screw, Hertz discovered an interesting phenomenon: to excite a spark in one of the coils, it is not necessary to connect a powerful battery to the second, the main thing is that a spark slips through the spark gap of the primary coil.

He conducted a series of experiments to confirm his observation.

3. Hertz vibrator

In his experiments, Hertz used a simple device, now called a Hertz vibrator, to produce electromagnetic waves.

This device is an open oscillatory circuit (picture on the right). The usual oscillatory circuit shown in the figure on the left (it can be called closed) is not suitable for emitting electromagnetic waves. The fact is that the alternating electric field is concentrated mainly in a very small region of space between the plates of the capacitor, and the magnetic field is concentrated inside the coil. In order for the radiation of electromagnetic waves to be sufficiently intense, the region of the alternating electromagnetic field must be large and not surrounded by metal plates. There is a similarity here with radiation sound waves. An oscillating string or tuning fork without a resonator box emit almost no radiation, since in this case air vibrations are excited in a very small region of space directly adjacent to the string or branches of the tuning fork.

The area in which an alternating electric field is created increases if the capacitor plates are moved apart. The capacity decreases. Simultaneous reduction of the plate area will further reduce the capacity. Reducing the capacitance will increase the natural frequency of this oscillatory circuit. To increase the frequency even more, you need to replace the coil with a straight wire without turns. The inductance of the straight wire is much less than the inductance of the coil. Continuing to move the plates apart and simultaneously reducing their sizes, we will arrive at an open oscillatory circuit. It's just a straight wire. IN open circuit the charges are not concentrated at the ends, but are distributed throughout the conductor. Current in this moment time in all sections of the conductor is directed in the same direction, but the current strength is not the same in different sections of the conductor. At the ends it is zero, and in the middle it reaches a maximum.

To excite oscillations in such a circuit, you need to cut the wire in the middle so that there remains a small air gap, called a spark gap. Thanks to this gap, both conductors can be charged to a high potential difference.

When the balls were given sufficiently large opposite charges, electrical discharge and in electrical circuit free electrical vibrations occur. After each recharge of the balls, a spark again jumps between them, and the process was repeated many times. Having placed at some distance from this circuit a coil of wire with two balls at the ends - a resonator - Hertz discovered that when a spark jumps between the balls of the vibrator, a small spark also appears between the balls of the resonator. Consequently, during electrical oscillations in an electrical circuit, a vortex alternating electromagnetic field appears in the space around it. This field creates an electric current in the secondary circuit (resonator).

Due to the small capacitance and inductance, the oscillation frequency is very high. The oscillations, of course, will be damped for two reasons: firstly, due to the presence of active resistance in the vibrator, which is especially high in the spark gap; secondly, due to the fact that the vibrator emits electromagnetic waves and loses energy. After the oscillations stop, the source again charges both conductors until breakdown of the spark gap occurs and everything repeats all over again. The figure below shows a Hertz vibrator connected in a series circuit with galvanic battery and a Ruhmkorff coil.

In one of the first vibrators assembled by the scientist, the ends were equipped with a spark gap in the middle copper wire 2.6 m long and 5 mm in diameter, movable tin balls with a diameter of 0.3 m were mounted as resonating ones. Subsequently, Hertz removed these balls to increase the frequency.

4. Ruhmkorff coil

The Ruhmkorff coil, which Heinrich Hertz used in his experiments, named after the German physicist Heinrich Ruhmkorff, consists of a cylindrical part with a central iron rod inside, on which a primary winding of thick wire is wound. Several thousand turns of a secondary winding made of very thin wire are wound on top of the primary winding. The primary winding is connected to the battery chemical elements and a capacitor. A breaker (buzzer) and a switch are inserted into the same circuit. The purpose of the breaker is to quickly alternately close and open the circuit. The result of this is that with each short circuit and opening in the primary circuit, strong instantaneous currents appear in the secondary winding: when interrupted - forward (in the same direction as the primary winding current) and when closed - reverse. When the primary winding is closed, an increasing current flows through it. The Ruhmkorff coil stores energy in the core in the form of a magnetic field. The magnetic field energy is:

C - magnetic flux,

L -- inductance of a coil or turn with current.

When the magnetic field reaches a certain value, the armature is attracted and the circuit opens. When the circuit is opened, a voltage surge (back EMF) occurs in both windings, directly proportional to the number of turns of the windings, large in value even in the primary winding, and even larger in the secondary winding, the high voltage of which breaks the air gap between the terminals of the secondary winding (air breakdown voltage is approximately equal to 3 kV by 1mm). The back EMF in the primary winding, through the low resistance of the battery of chemical cells, charges the capacitor C.

5. Experimenting with vibratorum

Heinrich Hertz experience

Hertz received electromagnetic waves by exciting a series of pulses of rapidly alternating current in a vibrator using a high voltage source. Oscillations of electric charges in a vibrator create an electromagnetic wave. Only oscillations in the vibrator are made not by one charged particle, but huge number electrons moving in concert.

In an electromagnetic wave, the vectors E? and B? are perpendicular to each other, and the vector E? lies in the plane passing through the vibrator, and vector B? perpendicular to this plane.

The figure shows the lines of electric and magnetic field strength around the vibrator at a fixed point in time: in horizontal plane The magnetic field induction lines are located, and the electric field strength lines are located in the vertical line. The waves are emitted with maximum intensity in the direction perpendicular to the vibrator axis. No radiation occurs along the axis.

Hertz was not able to discover this immediately. For his experiments, he darkened his room. And he walked around with a resonator, sometimes even through a magnifying glass, observing where in the room, relative to the generator, a spark would appear.

While experimenting with his vibrator, the scientist noticed that the seemingly completely natural pattern of weakening of the spark in the resonator with increasing distance to the source of oscillations is disrupted when the resonator is near walls or next to an iron stove.

After much thought, Hertz realized that the problem was the reflection of waves, and the strange behavior of the spark in the resonator near the walls was nothing more than interference. To confirm this, he attached a grounded metal sheet to the wall and installed a vibrator opposite it. With the resonator in his hands, he began to slowly move in a direction perpendicular to the wall. It turned out that periodically, at regular intervals, the resonator fell into dead zones in which there was no spark. These were zones in which the direct wave of the vibrator met a reflected wave of the opposite phase and was extinguished, which fully confirmed the presence of interference processes.

This caused genuine delight for everyone scientific world. He then easily demonstrated the linear propagation of radiation. When the path from the vibrator to the resonator was blocked with a metal screen, the sparks in the resonator completely disappeared. At the same time, it turned out that insulators (dielectrics) are transparent to electromagnetic waves. A complete analogy with the laws of light reflection was just as easily demonstrated - for this, a vibrator and a resonator were installed on one side of a grounded metal sheet, which played the role of a mirror, and the equality of the angles of incidence and reflection was checked.

The most demonstrative experiment was the demonstration of the possibility of refraction of electromagnetic radiation. For this, a prism made of asphalt weighing over a ton was used. The prism had the shape isosceles triangle with a side of 1.2 meters and an apex angle of 300. By directing the “electric beam” to an asphalt prism, Hertz recorded its deviation by 320, which corresponded to an acceptable refractive index value of 1.69.

In his experiments, Hertz not only experimentally proved the existence of electromagnetic waves, but also studied all the phenomena typical of any waves: reflection from metal surfaces, refraction in a large dielectric prism, interference of a traveling wave with a wave reflected from a metal mirror, etc. It was also possible to experimentally measure the speed of electromagnetic waves, which turned out to be equal speed light in a vacuum. These results provide one of the strongest proofs of the correctness electromagnetic theory Maxwell, according to which light is an electromagnetic wave.

Afterword

Just seven years after Hertz, electromagnetic waves found application in wireless communications. It is significant that the Russian inventor of radio Alexander Stepanovich Popov in his first radiogram in 1896 transmitted two words: “Heinrich Hertz”.

Lliterature

1. Library "Quantum", No. 1, 1988

2. Landsberg G.S., Optics - M.: FIZMATLIT, 2003, 848p.

3. Kaliteevsky N.I., “Wave optics”, M.: Vyssh. school, 1978, 383s

4. http://www.physbook.ru/

5. https://ru.wikipedia.org

6. http://ido.tsu.ru

7. http://alexandr4784.narod.ru

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Heinrich Rudolf Hertz (1857-1894) was born in Hamburg, the son of a lawyer who later became a senator. Hertz studied well, loved all subjects, wrote poetry and was passionate about working at lathe. Unfortunately, Hertz was hampered by poor health throughout his life.

In 1875, after graduating from high school, Hertz entered the Dresden University, and a year later the Munich University. technical school, but after the second year of study he realizes that he made a mistake in choosing a profession. His calling is not engineering, but science. He enters the University of Berlin, where his mentors are the physicists Helmholtz (1821-1894) and Kirchhoff (1824-1887). In 1880, Hertz graduated from the university early, receiving a doctorate. Since 1885 he has been a professor experimental physics Polytechnic Institute in Karlsruhe, where his famous experiments were carried out.

• In 1932 in the USSR, and in 1933 at a meeting of the International Electrotechnical Commission, the unit of frequency of a periodic process “hertz” was adopted, which was then included in international system SI units. 1 hertz is equal to one complete oscillation in one second.
• According to Hertz's contemporary, physicist J. Thomson (1856-1940), Hertz's work represents an amazing triumph of experimental skill, ingenuity, and at the same time an example of caution in drawing conclusions.
• Once, when Hertz’s mother told the master who taught the boy Hertz how to turn, that Heinrich had become a professor, he was very upset and remarked:

Oh, what a pity. He would make a great turner.

Hertz's experiments

Maxwell argued that electromagnetic waves have the properties of reflection, refraction, diffraction, etc. But any theory becomes proven only after it is confirmed in practice. But at that time, neither Maxwell himself nor anyone else knew how to experimentally obtain electromagnetic waves. This happened only after 1888, when G. Hertz experimentally discovered electromagnetic waves and published the results of his work.

Hertz vibrator. Open oscillatory circuit.

Hertz vibrator idea. Open oscillatory circuit.

From Maxwell's theory it is known

Only an accelerated moving charge can emit an electromagnetic wave,

that the energy of an electromagnetic wave is proportional to the fourth power of its frequency.

It is clear that charges move at an accelerated rate in an oscillatory circuit, so the easiest way is to use them to emit electromagnetic waves. But it is necessary to make sure that the frequency of oscillations of the charges becomes as high as possible. From Thomson's formula for the cyclic frequency of oscillations in a circuit it follows that to increase the frequency it is necessary to reduce the capacitance and inductance of the circuit.

The essence of the phenomena occurring in the vibrator is briefly as follows. The Ruhmkorff inductor creates a very high voltage, on the order of tens of kilovolts, at the ends of its secondary winding, which charges the spheres with charges of opposite signs. At a certain moment, an electric spark appears in the spark gap of the vibrator, making the resistance of its air gap so small that high-frequency damped oscillations arise in the vibrator, lasting as long as the spark exists. Since the vibrator is an open oscillatory circuit, electromagnetic waves are emitted.

The receiving ring was called a "resonator" by Hertz. Experiments have shown that by changing the geometry of the resonator - size, relative position and distance relative to the vibrator - it is possible to achieve “harmony” or “syntony” (resonance) between the source of electromagnetic waves and the receiver. The presence of resonance was expressed in the occurrence of sparks in the spark gap of the resonator in response to a spark arising in the vibrator. In Hertz's experiments, the sent spark was 3-7 mm long, and the spark in the resonator was only a few tenths of a millimeter. It was possible to see such a spark only in the dark, and even then using a magnifying glass.

“I work like a factory worker both in time and in character, I repeat every raise of my arm a thousand times,” the professor wrote in a letter to his parents in 1877. How difficult the experiments were with waves that were still long enough to study indoors (compared to light waves) can be seen from following examples. To be able to focus electromagnetic waves, a parabolic mirror was curved from a sheet of galvanized iron measuring 2x1.5 m. When the vibrator was placed at the focus of the mirror, a parallel stream of rays was created. To prove the refraction of these rays, a prism was made from asphalt in the form of an isosceles triangle with a side face of 1.2 m, a height of 1.5 m and a mass of 1200 kg.

Results of Hertz's experiments

After a huge series of labor-intensive and extremely cleverly staged experiments using the simplest, so to speak, available means, the experimenter achieved his goal. It was possible to measure the wavelengths and calculate the speed of their propagation. have been proven

presence of reflection,

refraction,

diffraction,

interference and polarization of waves.

electromagnetic wave speed measured

After his report on December 13, 1888 at the University of Berlin and publications in 1877 - 78. Hertz became one of the most popular scientists, and electromagnetic waves began to be commonly referred to as “Hertz’s rays.”

: Germany - Go. Source: vol. VIIIa (1893): Germany - Go, p. 559-563 ( · index) Other sources: MESBE :

Hertz experiments.- Theory of electrical and magnetic phenomena, created by the works of the best mathematicians of the first half of this century and until recently accepted by almost all scientists, basically assumed the existence of special weightless electric and magnetic fluids that have the property of acting at a distance. The principle of Newton's doctrine of universal gravity- “actio in distans” - remained leading in the teaching of electricity and magnetism. But already in the 30s genius Faraday, leaving without consideration the question of essence electricity and magnetism, regarding external actions they expressed completely different thoughts. The attraction and repulsion of electrified bodies, electrification through influence, the interaction of magnets and currents and, finally, the phenomena of Faraday induction do not represent manifestations directly at a distance of the properties inherent in electric and magnetic fluids, but are only consequences of special changes in the state of the medium in which these are located, apparently directly influencing each other electric charges, magnets or conductors with currents. Since all such actions are equally observed in emptiness, as well as in space filled with air or other matter, then in the changes produced by the processes of electrification and magnetization on air, Faraday saw the reason for these phenomena. Thus, just as through the emergence of special vibrations of the ether and the transmission of these vibrations from particle to particle, a light source illuminates any object remote from it, and in in this case Only through special disturbances in the medium of the same ether and the transmission of these disturbances from layer to layer do all electrical, magnetic and electromagnetic actions. A similar idea was the guiding principle in all of Faraday's research; she is most importantly and brought him to all his famous discoveries. But it was not soon and not easy that Faraday’s teachings became stronger in science. For decades, during which the phenomena discovered by him managed to undergo the most thorough and detailed study, Faraday’s basic ideas were either ignored or directly considered unconvincing and unproven. Only in the second half of the sixties did Faraday's talented follower, Clerk Maxwell, who died so early, appear, who interpreted and developed Faraday's theory, giving it a strictly mathematical character. Maxwell proved the necessity of existence final speed, with which the transfer of actions occurs through the intermediate medium electric current or magnet. This speed, according to Maxwell, should be equal to the speed at which light propagates in the medium under consideration. The environment involved in the transmission of electrical and magnetic actions, cannot be other than the same ether, which is allowed in the theory of light and radiant heat. The process of propagation of electrical and magnetic actions in space must be qualitatively the same as the process of propagation of light rays. All laws relating to light rays are fully applicable to electric rays. According to Maxwell, the phenomenon of light itself is an electrical phenomenon. A ray of light is a series of electrical disturbances, very small electrical currents, successively excited in the ether of the medium. What the change in the environment consists of under the influence of the electrification of some body, the magnetization of iron, or the formation of a current in some coil is still not known. Maxwell's theory does not yet make it possible to clearly imagine the very nature of the deformations it assumes. What is certain is that any change deformation of the medium produced in it under the influence of the electrification of bodies is accompanied by the emergence of magnetic phenomena in this environment and, conversely, any change in an environment of deformations resulting in it under the influence of some magnetic process, it is accompanied by the excitation of electrical actions. If at any point in the medium, deformed by the electrification of some body, an electric force is observed according to known direction, i.e., in this direction the one placed in the this place very small electrified ball, then with any increase or decrease in the deformation of the medium, together with an increase or decrease in the electric force at a given point, a magnetic force will appear in it in a direction perpendicular to the electric force - placed here magnetic pole will receive a push in a direction perpendicular to the electrical force. This is the consequence that follows from Maxwell's theory of electricity. Despite the enormous interest in the Faraday-Maxwell doctrine, it was met with doubt by many. Too bold generalizations flowed from this theory! The experiments of G. (Heinrich Hertz), carried out in 1888, finally confirmed the correctness of Maxwell's theory. G. managed, so to speak, to implement mathematical formulas Maxwell, it was actually possible to prove the possibility of the existence of electric, or, correctly, electromagnetic rays. As already noted, according to Maxwell's theory, the propagation of a light beam is essentially the propagation of electrical disturbances successively formed in the ether, quickly changing their direction. The direction in which such disturbances, such as deformations, are excited, according to Maxwell, is perpendicular to the light beam. From here it is obvious that the direct excitation in any body of electrical currents very quickly changing in direction, i.e. excitation in a conductor of electric currents of alternating direction and of very short duration should cause corresponding electrical disturbances in the ether surrounding this conductor, rapidly changing in their direction , that is, it should cause a phenomenon qualitatively quite similar to what a ray of light represents. But it has long been known that when an electrified body or a Leyden jar is discharged, a whole series of electrical currents are formed in the conductor through which the discharge occurs, alternately in one direction or the other. A discharging body does not immediately lose its electricity; on the contrary, during the discharge it is recharged several times with one or the other electricity according to the sign. Successive charges appearing on the body decrease only little by little in magnitude. Such categories are called oscillatory. The duration of existence in a conductor of two successive flows of electricity during such a discharge, i.e., the duration electrical vibrations, or otherwise, the time interval between two moments at which a discharging body receives the largest charges appearing on it in succession, can be calculated from the shape and size of the discharging body and the conductor through which such a discharge occurs. According to theory, this duration of electrical oscillations (T) expressed by the formula:

Here WITH stands for electrical capacity discharging body and L - self-induction coefficient conductor through which the discharge occurs (see). Both quantities are expressed according to the same system of absolute units. When using an ordinary Leyden jar, discharged through a wire connecting its two plates, the duration of electrical oscillations, i.e. T, determined in 100 and even 10 thousandths of a second. In his first experiments, G. electrified two metal balls (30 cm in diameter) differently and allowed them to discharge through a short and rather thick copper rod, cut in the middle, where an electric spark was formed between the two balls, which were mounted facing each other the ends of the two halves of the rod. Fig. 1 depicts a diagram of G.'s experiments (rod diameter 0.5 cm, ball diameter b And b′ 3 cm, the gap between these balls is about 0.75 cm and the distance between the centers of the balls S V S′ equals 1 m). Subsequently, instead of balls, G. used square metal sheets (40 cm on each side), which he placed in one plane. Charging of such balls or sheets was carried out using a functioning Ruhmkorff coil. The balls or sheets were charged many times per second from the coil and then discharged through a copper rod located between them, creating an electric spark in the gap between the two balls b And b′. The duration of the electrical oscillations excited in the copper rod exceeded a little one 100-thousandth of a second. In his further experiments, using, instead of sheets with halves of a copper rod attached to them, short thick cylinders with spherical ends, between which a spark jumped, G. received electrical vibrations, the duration of which was only about a thousand-millionth of a second. Such a pair of balls, sheets or cylinders, such vibrator, as G. calls it, from the point of view of Maxwellian theory, it is a center that propagates electromagnetic rays in space, that is, it excites electromagnetic waves in the ether, just like any light source that excites light waves around itself. But such electromagnetic rays or electromagnetic waves are not able to have an effect on the human eye. Only in the case when the duration of each electric train. the oscillation would reach only one 392-billionth of a second, the observer's eye would be impressed by these oscillations and the observer would see an electromagnetic beam. But to achieve such rapidity of electrical oscillations it is necessary vibrator, appropriate in size physical particles. So, to detect electromagnetic rays, special means are needed, apt expression W. Thomson (now Lord Kelvin), a special "electric eye". Such an “electric eye” was arranged by G in the simplest way. Let us imagine that at some distance from the vibrator there is another conductor. Disturbances in the ether excited by the vibrator should affect the state of this conductor. This conductor will be subject to sequential series impulses seeking to excite in it something similar to what caused such disturbances in the ether, i.e., seeking to form electrical currents in it that change in direction according to the speed of electrical oscillations in the vibrator itself. But impulses, successively alternating, are only able to contribute to each other when they are completely rhythmic with what they actually cause. electrical movements in such a conductor. After all, only in unison is a string tuned able to become noticeably vibrated by the sound emitted by another string, and thus able to appear independent sound source. So, the conductor must, so to speak, electrically resonate with the vibrator. Just as a string of given length and tension is capable of oscillations known in terms of speed when struck, so in each conductor from electrical impulse Electrical oscillations can only occur during very specific periods. Having bent copper wire of the appropriate dimensions in the form of a circle or rectangle, leaving only a small gap between the ends of the wire with small balls stolen on them (Fig. 2), of which one, by means of a screw, could approach or move away from the other, G. received, as he did named resonator to his vibrator (in most of his experiments, when the above-mentioned balls or sheets served as the vibrator, G. used copper wire 0.2 cm in diameter, bent in the form of a circle with a diameter of 35 cm, as a resonator). For a vibrator made of short thick cylinders, the resonator was a similar circle of wire, 0.1 cm thick and 7.5 cm in diameter. For the same vibrator, in his later experiments, G. built a resonator of a slightly different shape. Two straight wires, 0.5 cm dia. and 50 cm in length, located one on top of the other with a distance between their ends of 5 cm; from both ends of these wires facing each other, two other parallel wires of 0.1 cm in diameter are drawn perpendicular to the direction of the wires. and 15 cm in length, which are attached to the spark meter balls. No matter how weak the individual impulses themselves are from disturbances occurring in the ether under the influence of a vibrator, they, nevertheless, promoting each other in action, are able to excite already noticeable electrical currents in the resonator, manifested in the formation of a spark between the balls of the resonator. These sparks are very small (they reached 0.001 cm), but are quite sufficient to be a criterion for the excitation of electrical oscillations in the resonator and, by their size, serve as an indicator of the degree of electrical disturbance of both the resonator and the ether surrounding it. By observing the sparks appearing in such a resonator, Hertz examined at different distances and in various directions space around the vibrator. Leaving aside these experiments of G. and the results that were obtained by him, let us move on to research that confirmed the existence ultimate speed of propagation of electrical actions. Attached to one of the walls of the room in which the experiments were carried out was large sizes screen made of zinc sheets. This screen was connected to the ground. At a distance of 13 meters from the screen, a vibrator made of plates was placed so that the planes of its plates were parallel to the plane of the screen and the middle between the vibrator balls was opposite the middle of the screen. If a vibrator, during its operation, periodically excites electrical disturbances in the surrounding ether and if these disturbances propagate in the medium not instantly, but with a certain speed, then, having reached the screen and reflected back from the latter, like sound and light disturbances, these disturbances, together with those which are sent to the screen by a vibrator, form in the ether, in the space between the screen and the vibrator, a state similar to that which occurs under similar conditions due to the interference of counterpropagating waves, i.e. in this space the disturbances will take on the character "standing waves"(see Waves). The state of the air in places corresponding to "nodes" And "antinodes" of such waves, obviously, should differ significantly. Placing his resonator with its plane parallel to the screen and so that its center was on a line drawn from the middle between the vibrator balls normal to the plane of the screen, G. observed at different distances of the resonator from the screen, the sparks in it are very different in length. Near the screen itself, almost no sparks appear in the resonator, also at distances equal to 4.1 and 8.5 m. On the contrary, sparkles are greatest when the resonator is placed at distances from the screen equal to 1.72 m, 6.3 m and 10.8 m. G. concluded from his experiments that on average 4.5 m separate from each other those positions of the resonator in which the phenomena observed in it, i.e., sparks, turn out to be closely identical. G. obtained exactly the same thing with a different position of the resonator plane, when this plane was perpendicular to the screen and passed through a normal line drawn to the screen from the middle between the vibrator balls and when axis of symmetry the resonator (i.e., its diameter passing through the middle between its balls) was parallel to this normal. Only with this position of the resonator plane maxima sparks in it were obtained where, in the previous position of the resonator, minima, and back. So 4.5 m corresponds to the length "standing electromagnetic waves" arising between the screen and the vibrator in a space filled with air (the opposite phenomena observed in the resonator in its two positions, i.e., maxima sparks in one position and minima in the other, are fully explained by the fact that in one position of the resonator electrical oscillations are excited in it electrical forces, so-called electrical deformations in the ether; in another position they are caused as a consequence of the occurrence magnetic forces, i.e. they get excited magnetic deformations).

According to the length of the “standing wave” (l) and by time (T), corresponding to one complete electrical oscillation in the vibrator, based on the theory of the formation of periodic (wave-like) disturbances, it is easy to determine the speed (v), with which such disturbances are transmitted in the air. This speed v = 2 l T . (\displaystyle v=(\frac (2l)(T)).) In G.'s experiments: l= 4.5 m, T= 0.000000028″. From here v= 320,000 (approximately) km per second, i.e. very close to the speed of light propagating in the air. G. studied the propagation of electrical vibrations in conductors, that is, in wires. For this purpose, an insulated copper plate of the same type was placed parallel to one vibrator plate, from which came a long wire stretched horizontally (Fig. 3). In this wire, due to the reflection of electrical vibrations from its insulated end, “ standing waves", the distribution of "nodes" and "antinodes" of which along the wire G. found using a resonator. G. derived from these observations for the speed of propagation of electrical vibrations in a wire a value equal to 200,000 km per second. But this definition is not correct. According to Maxwell's theory, in this case the speed should be the same as for air, i.e. it should be equal to the speed of light in air. (300,000 km per second). Experiments carried out after G. by other observers confirmed the position of Maxwell's theory.

Having a source of electromagnetic waves, a vibrator, and a means of detecting such waves, a resonator, G. proved that such waves, like light waves, are subject to reflections and refractions and that electrical disturbances in these waves are perpendicular to the direction of their propagation, i.e., he discovered polarization in electric rays. For this purpose, he placed a vibrator that produces very fast electrical oscillations (a vibrator made of two short cylinders) in the focal line of a parabolic cylindrical mirror made of zinc; in the focal line of another similar mirror he placed a resonator, as described above, made of two straight wires . By directing electromagnetic waves from the first mirror onto some flat metal screen, G., with the help of another mirror, was able to determine the laws of reflection of electric waves, and by forcing these waves to pass through large prism, prepared from asphalt, determined their refraction. The laws of reflection and refraction turned out to be the same as for light waves. Using these same mirrors, G. proved that electric rays polarized, when the axes of two mirrors placed opposite each other were parallel under the action of a vibrator, sparks were observed in the resonator. When one of the mirrors was rotated 90° around the direction of the rays, i.e., the axes of the mirrors made a right angle to each other, any trace of sparks in the resonator disappeared.

In this way, G.'s experiments proved the correctness of Maxwell's position. The G. vibrator, like a light source, emits energy into the surrounding space, which, through electromagnetic rays, is transmitted to everything that is able to absorb it, transforming this energy into another form accessible to our senses. Electromagnetic rays the quality is quite similar to rays of heat or light. Their difference from the latter lies only in the lengths of the corresponding waves. The length of light waves is measured in ten thousandths of a millimeter, while the length of electromagnetic waves excited by vibrators is expressed in meters. The phenomena discovered by G. later served as the subject of research by many physicists. In general, G.'s conclusions are fully confirmed by these studies. Now we know, moreover, that the speed of propagation of electromagnetic waves, as follows from Maxwell’s theory, changes along with changes in the medium in which such waves propagate. This speed is inversely proportional K , (\displaystyle (\sqrt (K)),) Where K the so-called dielectric constant of a given medium. We know that when electromagnetic waves propagate along conductors, electrical vibrations are “damped”; that when electric rays are reflected, their “voltage” follows the laws given by Fresnel for light rays, etc. G.’s articles concerning the phenomenon under consideration, collected together, now published under the title: H. Hertz, “Untersuchungen über die Ausbreitung der elektrischen Kraft” (Lpts., 1892).