Who discovered electromagnetic waves? Electromagnetic waves - table. Types of electromagnetic waves

Electromagnetic waves (the table of which will be given below) are perturbations of magnetic and electric fields that are distributed in space. There are several types. The study of these perturbations deals with physics. Electromagnetic waves are formed due to the fact that an electric alternating field generates a magnetic field, and it, in turn, generates an electric one.

History of research

The first theories, which can be considered the oldest variants of the hypotheses about electromagnetic waves, are at least Huygens' times. At that time, the assumptions reached a marked quantitative development. Huygens in 1678 issued in some way "sketch" of the theory - "Treatise on the Light." In 1690 he also published another remarkable work. It contained a qualitative theory of reflection and refraction in the form in which it is today represented in school textbooks ("Electromagnetic Waves", Grade 9).

Together with this, the Huygens principle was formulated. With his help, it became possible to study the motion of the wave front. This principle later found its development in the writings of Fresnel. The Huygens-Fresnel principle was of particular importance in the theory of diffraction and the wave theory of light.

In the 1660s and 1670s, a great experimental and theoretical contribution was made to the studies by Hooke and Newton. Who discovered electromagnetic waves? Who conducted the experiments proving their existence? What are the types of electromagnetic waves? About this further.

Justification of Maxwell

Before talking about who discovered electromagnetic waves, it should be said that the first scientist, who generally predicted their existence, was Faraday. His hypothesis he put forward in 1832-th year. The construction of the theory was subsequently handled by Maxwell. By 1865, he completed this work. As a result, Maxwell strictly formulated the theory mathematically, justifying the existence of the phenomena under consideration. He also determined the speed of propagation of electromagnetic waves, coinciding with the then used value of the light speed. This, in turn, allowed him to substantiate the hypothesis that light is one of the types of radiation considered.

Experimental detection

The theory of Maxwell found its confirmation in the experiments of Hertz in 1888. Here it should be said that the German physicist conducted his experiments to refute the theory, despite its mathematical justification. However, thanks to his experiments, Hertz became the first to discover electromagnetic waves practically. In addition, during his experiments, the scientist identified the properties and characteristics of radiation.

Electromagnetic oscillations and Hertz waves were obtained by exciting a series of pulses of a rapidly varying flow in a vibrator with the help of a source of increased voltage. High-frequency flows can be detected by means of a circuit. The frequency of oscillation will be the higher, the higher its capacitance and inductance. However, the higher frequency is not a guarantee of intensive flow. To conduct their experiments, Hertz used a fairly simple device, which today is called - the "Hertz vibrator." The device is an open-type oscillating circuit.

The scheme of the Hertz experiment

Registration of emissions was carried out using a receiving vibrator. This device had the same design as the radiating device. Under the influence of an electromagnetic wave of an electric alternating field, a current oscillation was excited in the receiving device. If in this device its own frequency and the frequency of the flow coincided, then a resonance appeared. As a result, the disturbances in the receiving device occurred with a larger amplitude. Discovered by their researcher, watching sparks between the conductors in a small space.

Thus, Hertz became the first who discovered electromagnetic waves, proved their ability to reflect well from the conductors. The formation of standing radiation was practically justified. In addition, Hertz determined the speed of propagation of electromagnetic waves in the air.

Study of characteristics

Electromagnetic waves propagate in almost all media. In a space that is filled with matter, the radiation can in some cases be distributed fairly well. But at the same time they change their behavior somewhat.

Electromagnetic waves in vacuum are determined without damping. They are allocated to any, arbitrarily long distance. The main characteristics of waves include polarization, frequency and length. The properties are described in terms of electrodynamics. However, more specific sections of physics deal with the characteristics of radiation in certain regions of the spectrum . To them, for example, you can include optics.

The study of hard electromagnetic radiation of the short-wavelength spectral end is concerned with the separation of high energies. Taking into account modern concepts, dynamics ceases to be an independent discipline and is combined with weak interactions in one theory.

Theories used in the study of properties

Today, there are various methods that facilitate the modeling and investigation of manifestations and properties of oscillations. The most fundamental of the tested and completed theories is quantum electrodynamics. From it, through these or other simplifications, it becomes possible to obtain the following techniques, which are widely used in various fields.

The description of relatively low-frequency radiation in a macroscopic medium is realized by means of classical electrodynamics. It is based on the Maxwell equations. At the same time there are simplifications in applied applications. Optical study uses optics. The wave theory is used in cases where some parts of the optical system are approximately in size close to the wavelengths. Quantum optics is used when processes of scattering, absorption of photons are essential.

Geometric optical theory is the limiting case in which negligible wavelengths are allowed. There are also several applied and fundamental sections. For example, they include astrophysics, biology of visual perception and photosynthesis, photochemistry. How are electromagnetic waves classified? A table that clearly shows the distribution of the groups is presented below.

Classification

There are frequency ranges of electromagnetic waves. There are no sharp transitions between them, sometimes they overlap each other. The boundaries between them are rather arbitrary. Due to the fact that the stream is distributed continuously, the frequency is rigidly associated with the length. Below are the ranges of electromagnetic waves.

Ultra-short radiation is usually divided into micrometer (submillimeter), millimeter, centimeter, decimeter, meter. If the wavelength of the electromagnetic radiation is less than a meter, then it is customarily called an ultrahigh-frequency oscillation (SHF).

Types of electromagnetic waves

The ranges of electromagnetic waves are presented above. What are the different types of flows? The group of ionizing radiation includes gamma and X-rays. At the same time, it must be said that ultraviolet, and even visible light, can ionize atoms. The boundaries in which gamma and X-ray fluxes are found are determined very arbitrarily. As a general orientation, the limits of 20 eV - 0.1 MeV are accepted. Gamma fluxes in a narrow sense are emitted by the nucleus, and X-ray fluxes are emitted by the electron atomic shell in the process of knocking out electrons from low-lying orbits. However, this classification is not applicable to hard radiations generated without the participation of nuclei and atoms.

X-ray fluxes are formed when the charged fast particles (protons, electrons, etc.) are slowed down and due to the processes that occur inside the atomic electron shells. Gamma-oscillations arise as a result of processes inside the atomic nuclei and in the transformation of elementary particles.

Radio streams

Due to the large value of the lengths, consideration of these waves can be made without taking into account the atomistic structure of the medium. As an exception, only the shortest flows that adjoin the infrared region of the spectrum. In the radio range, the quantum properties of oscillations are rather weakly manifested. Nevertheless, they must be taken into account, for example, when analyzing the molecular standards of time and frequency during cooling of equipment to a temperature of several kelvins.

Quantum properties are also taken into account when describing generators and amplifiers of millimeter and centimeter ranges. The radio stream is formed during the movement of alternating current through conductors of the appropriate frequency. And the passing electromagnetic wave in space excites an alternating current corresponding to it. This property is used in the design of antennas in radio engineering.

Visible Streams

The ultraviolet and infrared visible radiation is in the broadest sense the so-called optical part of the spectrum. The isolation of this region is caused not only by the proximity of the corresponding zones, but also by the similarity of the instruments used in the study and developed primarily during the study of visible light. These include, in particular, mirrors and lenses for focusing radiation, diffraction gratings, prisms, and others.

The frequencies of optical waves are comparable with those of molecules and atoms, and their lengths with intermolecular distances and molecular dimensions. Therefore, phenomena that are due to the atomistic structure of matter become significant in this area. For the same reason, light, along with wave ones, also has quantum properties.

The appearance of optical flows

The most famous source is the Sun. The surface of the star (photosphere) has a temperature of 6000 ° Kelvin and emits bright white light. The highest value of the continuous spectrum is located in the "green" zone - 550 nm. There is also a maximum of visual sensitivity. Oscillations of the optical range occur when the bodies are heated. Infrared streams are therefore also called thermal.

The more heated the body, the higher the frequency, where the maximum of the spectrum is located. With a certain increase in temperature, we observe burning (glow in the visible range). At the same time, red color first appears, then yellow and then on. The creation and recording of optical flows can occur in biological and chemical reactions, one of which is used in photography. For most creatures living on Earth, photosynthesis acts as a source of energy. This biological reaction occurs in plants under the influence of optical solar radiation.

Features of electromagnetic waves

The properties of the medium and the source affect the characteristics of the streams. Thus, in particular, the time dependence of the fields that determines the type of flow is established. For example, if you change the distance from the vibrator (with increasing), the radius of curvature becomes larger. As a result, a plane electromagnetic wave is formed. Interaction with the substance also occurs in different ways. The processes of absorption and emission of fluxes, as a rule, can be described with the help of classical electrodynamic relations. For waves of the optical region and for hard rays, the more quantum nature should be taken into account.

Thread Sources

Despite the physical difference, everywhere - in a radioactive substance, a television transmitter, an incandescent lamp - electromagnetic waves are excited by electric charges that move with acceleration. There are two main types of sources: microscopic and macroscopic. In the former, a jump-like transition of charged particles from one level to another takes place inside molecules or atoms.

Microscopic sources emit x-ray, gamma, ultraviolet, infrared, visible, and in some cases also long-wave radiation. As an example of the latter, we can cite the line of the hydrogen spectrum, which corresponds to a wave of 21 cm. This phenomenon is of particular importance in radio astronomy.

Sources of macroscopic type are radiators, in which periodic synchronous oscillations are performed by free electrons of conductors. In systems of this category, flows from millimeters to the longest ones (in power lines) occur.

Structure and strength of flows

Electric charges moving with acceleration and periodically changing currents have an effect on each other with certain forces. The direction and magnitude are dependent on factors such as the size and configuration of the area in which the currents and charges are contained, their relative direction and magnitude. A significant influence is also exerted by the electrical characteristics of a particular medium, as well as changes in the concentration of charges and the distribution of source currents.

In connection with the overall complexity of posing the problem, it is impossible to present the law of forces in the form of a single formula. The structure, called the electromagnetic field and considered as a mathematical object if necessary, is determined by the distribution of charges and currents. It, in turn, is created by a given source when boundary conditions are taken into account. The conditions are determined by the shape of the interaction zone and the characteristics of the material. If we are talking about unlimited space, these circumstances are supplemented. As a special additional condition in such cases, the radiation condition appears. Due to it, the "correctness" of the field behavior at infinity is guaranteed.

Chronology of the study

The corpuscular-kinetic theory of Lomonosov in some of its positions anticipates certain postulates of the theory of the electromagnetic field: the rotational motion of particles, the "swirling" (wave) theory of light, its generality with the nature of electricity, etc. Infrared fluxes were discovered in the 1800s Herschel (English scientist), and in the following year, 1801, Ritter described the ultraviolet. Radiation of a shorter than the ultraviolet range was discovered by Roentgen in 1895, on November 8. Subsequently, it was called x-ray.

The influence of electromagnetic waves has been studied by many scientists. However, Narkevich-Iodko (the Belarusian scientist) became the first who investigated the possibilities of flows, the scope of their application. He studied the properties of flows in relation to practical medicine. Gamma radiation was discovered by Paul Willard in 1900-th year. In the same period, Planck carried out theoretical studies of the properties of the black body. In the process of studying it, the process was quantized. His work was the beginning of the development of quantum physics. Subsequently, several works of Planck and Einstein were published. Their research led to the formation of such a thing as a photon. This, in turn, marked the beginning of the creation of the quantum theory of electromagnetic flows. Its development continued in the works of leading scientific figures of the twentieth century.

Further research and work on the quantum theory of electromagnetic radiation and its interaction with matter led to the formation of quantum electrodynamics in the form in which it exists today. Among the outstanding scientists who studied this issue, we should mention, in addition to Einstein and Planck, Bohr, Bose, Dirac, de Broglie, Heisenberg, Tomonaga, Schwinger, Feynman.

Conclusion

The importance of physics in the modern world is large enough. Virtually all that is used today in human life, has emerged through the practical use of research by great scientists. The discovery of electromagnetic waves and their study, in particular, led to the creation of conventional, and subsequently mobile phones, radio transmitters. Of particular importance is the practical application of such theoretical knowledge in the fields of medicine, industry, and technology.

Such widespread use is explained by the quantitative nature of science. All physical experiments rely on measurements, comparing the properties of the phenomena studied with the available standards. It is for this purpose that a set of measuring instruments and units is developed within the discipline. A number of regularities are common to all existing material systems. For example, the laws of conservation of energy are considered general physical laws.

Science in general is called in many cases fundamental. This is due, first of all, to the fact that other disciplines give descriptions that, in turn, obey the laws of physics. Thus, in chemistry, atoms, substances formed from them, and transformations are studied. But the chemical properties of bodies are determined by the physical characteristics of molecules and atoms. These properties describe such branches of physics as electromagnetism, thermodynamics, and others.