What is an electron wave. Electromagnetic radiation

Few people know that radiation of an electromagnetic nature permeates the entire Universe. Electromagnetic waves arise when it spreads in space. Depending on the vibration frequency of the waves, they are conditionally divided into visible light, radio frequency spectrum, infrared ranges, etc. The practical existence of electromagnetic waves was experimentally proven in 1880 by the German scientist G. Hertz (by the way, the unit of measurement of frequency is named after him).

From a physics course we know what it is special kind matter. Even though only a small part of it can be seen with vision, its influence on the material world is enormous. Electromagnetic waves are the sequential propagation in space of interacting vectors of magnetic and electric field strength. However, the word “distribution” in in this case not entirely correct: we are talking, rather, about a wave-like disturbance of space. The reason that generates electromagnetic waves is the appearance in space of something changing over time. electric field. And, as you know, there is a direct connection between electric and magnetic fields. It is enough to remember the rule according to which there is a magnetic field around any current-carrying conductor. A particle affected by electromagnetic waves begins to oscillate, and since there is movement, it means that there is radiation of energy. The electric field is transferred to a neighboring particle at rest, resulting in a field being generated again electrical nature. And since the fields are interconnected, the magnetic field appears next. The process spreads like an avalanche. In this case, there is no real movement, but only vibrations of particles.

About the opportunity practical use Physicists have been thinking about this for a long time. IN modern world The energy of electromagnetic waves is so widely used that many do not even notice it, taking it for granted. A striking example- radio waves, without which the operation of televisions and mobile phones.

The process occurs as follows: a modulated metal conductor of a special shape (antenna) is constantly transmitted. Due to the properties of the electric current, an electric and then a magnetic field arises around the conductor, resulting in the emission of electromagnetic waves. Since they are modulated, they carry a certain order, encoded information. To catch the required frequencies, a receiving antenna of a special design is installed at the recipient. It allows you to select the required frequencies from the general electromagnetic background. Once on a metal receiver, the waves are partially converted into electricity original modulation. Next, they go to the amplifying unit and control the operation of the device (they move the speaker diffuser, rotate the electrodes in TV screens).

The current produced from electromagnetic waves can be easily seen. To do this, it is enough for the bare core of the cable running from the antenna to the receiver to touch the common mass (heating radiator). At this moment, a spark jumps between the ground and the core - this is a manifestation of the current generated by the antenna. Its value is greater, the closer and more powerful the transmitter. Also Antenna configuration has a significant impact.

Another manifestation of electromagnetic waves that many encounter every day in everyday life is the use microwave oven. Rotating field strength lines cross the object and transfer part of their energy, heating it.

Electromagnetic waves are the result of many years of debate and thousands of experiments. Proof of the presence of forces of natural origin capable of upending the existing society. This is the actual acceptance of a simple truth - we know too little about the world in which we live.

Physics is the queen among the natural sciences, capable of providing answers to questions about the origin of not only life, but also the world itself. It gives scientists the ability to study the electric and magnetic fields, the interaction of which generates EMF (electromagnetic waves).

What is an electromagnetic wave

Not long ago, the film “War of Currents” (2018) was released on the screens of our country, which, with a touch of fiction, tells about the dispute between two great scientists Edison and Tesla. One tried to prove the benefits of direct current, the other - of alternating current. This long battle ended only in the seventh year of the twenty-first century.

At the very beginning of the “battle”, another scientist, working on the theory of relativity, described electricity and magnetism as similar phenomena.

In the thirtieth year of the nineteenth century, the English-born physicist Faraday discovered the phenomenon electromagnetic induction and introduced the term of unity of the electric and magnetic fields. He also argued that movement in this field is limited by the speed of light.

A little later, the theory of the English scientist Maxwell said that electricity causes a magnetic effect, and magnetism causes the appearance of an electric field. Since both of these fields move in space and time, they form disturbances - that is, electromagnetic waves.

To put it simply, an electromagnetic wave is a spatial disturbance of an electrical magnetic field.

The existence of electromagnetic waves was experimentally proven by the German scientist Hertz.

Electromagnetic waves, their properties and characteristics

Electromagnetic waves are characterized by the following factors:

length (quite wide range);
frequency;
intensity (or amplitude of vibration);
amount of energy.

The main property of all electromagnetic radiation is a measurement of wavelength (in vacuum), usually specified in nanometers for the visible light spectrum.

Each nanometer represents a thousandth of a micrometer and is measured by the distance between two consecutive peaks (vertices).

The corresponding wave emission frequency is the number of sinusoidal oscillations and inverse proportionality wavelength.

Frequency is usually measured in Hertz. Thus, longer waves correspond to lower frequency radiation, and shorter waves correspond to high frequency radiation.

Basic properties of waves:

refraction;
reflection;
absorption;
interference.

Electromagnetic wave speed

The actual speed of propagation of an electromagnetic wave depends on the material of the medium, its optical density and the presence of factors such as pressure.

In addition, different materials have different densities of “packing” of atoms; the closer they are located, the shorter the distance and higher the speed. As a result, the speed of an electromagnetic wave depends on the material through which it travels.

Similar experiments are carried out in the hadron collider, where the main instrument of influence is a charged particle. Studying electromagnetic phenomena occurs there at the quantum level, when light is decomposed into tiny particles - photons. But quantum physics is a separate topic.

According to the theory of relativity, the highest speed of wave propagation cannot exceed light speed. Maxwell described the finiteness of the speed limit in his works, explaining this by the presence of a new field - the ether. Modern official science has not yet studied such a relationship.

Electromagnetic radiation and its types

Electromagnetic radiation consists of electromagnetic waves, which are observed as oscillations of electric and magnetic fields, propagating at the speed of light (300 km per second in a vacuum).

When EM radiation interacts with matter, its behavior changes qualitatively as the frequency changes. Why does it transform into:

Radio emissions. At radio frequencies and microwave frequencies, em radiation interacts with matter mainly in the form of a common set of charges that are distributed over a large number affected atoms.
Infrared radiation. Unlike low-frequency radio and microwave radiation, an infrared emitter typically interacts with dipoles present in individual molecules that change at the ends of a chemical bond at the atomic level as they vibrate.
Visible light emission. As the frequency increases in the visible range, the photons have enough energy to change the bonded structure of some individual molecules.
Ultraviolet radiation. The frequency increases. Ultraviolet photons now contain enough energy (more than three volts) to act doubly on the bonds of molecules, constantly rearranging them chemically.
Ionizing radiation. At the highest frequencies and shortest wavelengths. The absorption of these rays by matter affects the entire gamma spectrum. The most famous effect is radiation.

What is the source of electromagnetic waves

The world, according to the young theory of the origin of everything, arose due to impulse. He released colossal energy, which was called the big bang. This is how the first em-wave appeared in the history of the universe.

Currently, sources of disturbance formation include:

EMW is emitted by an artificial vibrator;
the result of vibration of atomic groups or parts of molecules;
if there is an impact on the outer shell of the substance (at the atomic-molecular level);
effect similar to light;
during nuclear decay;
consequence of electron braking.

Scale and application of electromagnetic radiation

The radiation scale refers to a large wave frequency range from 3·10 6 ÷10 -2 to 10 -9 ÷ 10 -14.

Each part of the electromagnetic spectrum has a wide range of applications in our daily lives:

Short waves (microwaves). These electric waves are used as a satellite signal because they are able to bypass the earth's atmosphere. Also, a slightly enhanced version is used for heating and cooking in the kitchen - this is a microwave oven. The cooking principle is simple - under the influence of microwave radiation, water molecules are absorbed and accelerated, causing the dish to heat up.
Long disturbances are used in radio technology (radio waves). Their frequency does not allow the passage of clouds and the atmosphere, thanks to which FM radio and television are available to us.
Infrared disturbance is directly related to heat. It is almost impossible to see him. Try to notice, without special equipment, the beam from the control panel of your TV, stereo or car stereo. Devices capable of reading such waves are used in the armies of countries (night vision devices). Also in inductive cookers in kitchens.
Ultraviolet is also related to heat. The most powerful natural “generator” of such radiation is the sun. It is due to the action of ultraviolet radiation that a tan forms on human skin. In medicine, this type of waves is used to disinfect instruments, killing germs and.
Gamma rays are the most powerful type of radiation, in which short-wave disturbance with high frequency is concentrated. The energy contained in this part of the electromagnetic spectrum gives the rays greater penetrating power. Applicable in nuclear physics– peaceful, nuclear weapons – combat use.

The influence of electromagnetic waves on human health

Measuring the effects of emf on humans is the responsibility of scientists. But you don't need to be an expert to appreciate the intensity ionizing radiation– it provokes changes at the level of human DNA, which entails such serious illnesses like oncology.

It is not for nothing that the harmful effects of the Chernobyl nuclear power plant disaster are considered one of the most dangerous for nature. Several square kilometers of the once beautiful territory have become a zone of complete exclusion. Until the end of the century, the explosion at the Chernobyl nuclear power plant poses a danger until the half-life of radionuclides ends.

Some types of emwaves (radio, infrared, ultraviolet) do not cause severe harm to humans and only cause discomfort. After all, we practically cannot feel the earth’s magnetic field, but emf from a mobile phone can cause a headache (impact on the nervous system).

In order to protect your health from electromagnetism, you should simply use reasonable precautions. Instead of hundreds of hours computer game go out for a walk.

This is the process of propagation of electromagnetic interaction in space.
Electromagnetic waves are described by Maxwell's equations, common to electromagnetic phenomena. Even in the absence of electric charges and currents in space, Maxwell's equations have non-zero solutions. These solutions describe electromagnetic waves.
In the absence of charges and currents, Maxwell’s equations take the following form:

By applying the rot operation to the first two equations, you can obtain separate equations for determining the strength of the electric and magnetic fields

These equations have the typical form of wave equations. Their solutions are a superposition of expressions of the following type

Where – A certain vector, which is called the wave vector, ? – a number called the cyclic frequency, ? – phase. The quantities are the amplitudes of the electric and magnetic components of the electromagnetic wave. They are mutually perpendicular and equal in absolute value. The physical interpretation of each of the introduced quantities is given below.
In a vacuum, an electromagnetic wave travels at a speed called the speed of light. The speed of light is a fundamental physical constant, which is denoted Latin letter c. According to the basic postulate of the theory of relativity, the speed of light is maximum possible speed transmission of information or body movement. This speed is 299,792,458 m/s.
An electromagnetic wave is characterized by frequency. Distinguish between line frequency? and cyclic frequency? = 2??. Depending on the frequency, electromagnetic waves belong to one of the spectral ranges.
Another characteristic of an electromagnetic wave is the wave vector. The wave vector determines the direction of propagation of an electromagnetic wave, as well as its length. The absolute value of the wave vector is called the wave number.
Electromagnetic wavelength? = 2? / k, where k is the wave number.
The length of an electromagnetic wave is related to frequency through the law of dispersion. In emptiness this connection is simple:

?? = c.

This relationship is often written in the form

? = c k.

Electromagnetic waves with the same frequency and wave vector can differ in phase.
In a vacuum, the strength vectors of the electric and magnetic fields of an electromagnetic wave are necessarily perpendicular to the direction of propagation of the wave. Such waves are called transverse waves. Mathematically, this is described by the equations and . In addition, the electric and magnetic field strengths are perpendicular to each other and are always equal in absolute value at any point in space: E = H. If you choose a coordinate system so that the z axis coincides with the direction of propagation of the electromagnetic wave, there are two different possibilities for the directions electric field strength vectors. If the eclectic field is directed along the x-axis, then the magnetic field will be directed along the y-axis, and vice versa. These two different possibilities are not mutually exclusive and correspond to two different polarizations. This issue is discussed in more detail in the article Wave Polarization.
Spectral ranges with highlighted visible light Depending on the frequency or wavelength (these quantities are related to each other), electromagnetic waves are classified into different ranges. Waves in different ranges interact in different ways with physical bodies.
Electromagnetic waves with the lowest frequency (or longest wavelength) are classified as radio range. The radio range is used to transmit signals over a distance using radio, television, and mobile phones. Radar operates in the radio range. The radio range is divided into meter, dicemeter, centimeter, millimeter, depending on the length of the Electromagnetic wave.
Electromagnetic waves most likely belong to the infrared range. The thermal radiation of the body lies in the infrared range. Registration of this vibration is the basis of the operation of night vision devices. Infrared waves are used to study thermal vibrations in bodies and help establish atomic structure solids, gases and liquids.
Electromagnetic radiation with wavelengths between 400 nm and 800 nm belongs to the visible light range. Depending on the frequency and wavelength, visible light varies in color.
Wavelengths less than 400 nm are called ultraviolet. The human eye cannot distinguish them, although their properties do not differ from the properties of visible waves. The higher frequency, and, consequently, the energy of the quanta of such light leads to a more destructive effect of ultraviolet waves on biological objects. Earth's surface protected from harmful effects ultraviolet waves by the ozone layer. For additional protection, nature has endowed people with dark skin. However, humans need ultraviolet rays to produce vitamin D. This is why people in northern latitudes, where the intensity of ultraviolet waves is less, have lost their dark skin color.
Electromagnetic waves of higher frequency belong to x-ray range. They are called so because Roentgen discovered them while studying the radiation that is produced when electrons decelerate. In foreign literature, such waves are usually called X-rays respecting Roentgen's wishes that the rays not be named after him. X-ray waves interact weakly with matter, being absorbed more strongly where the density is greater. This fact is used in medicine for X-ray fluorography. X-ray waves are also used for elemental analysis and studying the structure of crystalline bodies.
The highest frequency and shortest length have ?-rays. Such rays are formed as a result nuclear reactions and reactions between elementary particles. ?-rays have a great destructive effect on biological objects. However, they are used in physics to study various characteristics atomic nucleus.
The energy of an electromagnetic wave is determined by the sum of the energies of the electric and magnetic fields. The energy density at a certain point in space is given by the expression:

The time-averaged energy density is equal to.

Where E 0 = H 0 is the amplitude of the wave.
The energy flux density of the electromagnetic wave is important. In particular, it determines the luminous flux in optics. The energy flux density of an electromagnetic wave is specified by the Umov-Poynting vector.

The propagation of electromagnetic waves in a medium has a number of features compared to propagation in emptiness. These features are associated with the properties of the medium and generally depend on the frequency of the electromagnetic wave. The electric and magnetic components of the wave cause polarization and magnetization of the medium. This response of the medium is different in the case of low and high frequencies. At a low frequency of the electromagnetic wave, the electrons and ions of the substance have time to respond to changes in the intensity of the electric and magnetic fields. The response of the medium tracks temporal fluctuations into waves. At a high frequency, the electrons and ions of the substance do not have time to move during the period of oscillation of the wave fields, and therefore the polarization and magnetization of the medium is much less.
A low-frequency electromagnetic field does not penetrate metals, where there are many free electrons, which are displaced in this way and completely dampen the electromagnetic wave. An electromagnetic wave begins to penetrate the metal at a frequency exceeding a certain frequency, which is called the plasma frequency. At frequencies lower than the plasma frequency, the electromagnetic wave can penetrate the surface layer of the metal. This phenomenon is called the skin effect.
In dielectrics, the dispersion law of the electromagnetic wave changes. If electromagnetic waves propagate in a vacuum with a constant amplitude, then in the medium they are attenuated due to absorption. In this case, the wave energy is transferred to electrons or ions of the medium. In total, the dispersion law in the absence of magnetic effects takes the form

Where wave number k is a complex quantity, the imaginary part of which describes the decrease in the amplitude of the electromagnetic wave, is the frequency-dependent complex dielectric constant of the medium.
In anisotropic media, the direction of the electric and magnetic field strength vectors is not necessarily perpendicular to the direction of wave propagation. However, the direction of the electric and magnetic induction vectors retains this property.
Under certain conditions, another type of electromagnetic wave can propagate in a medium - a longitudinal electromagnetic wave, for which the direction of the electric field strength vector coincides with the direction of propagation of the wave.
At the beginning of the twentieth century, in order to explain the spectrum of black body radiation, Max Planck proposed that electromagnetic waves are emitted by quanta with energy proportional to frequency. A few years later, Albert Einstein, explaining the phenomenon of the photoelectric effect, expanded this idea, suggesting that electromagnetic waves are absorbed by the same quanta. Thus, it became clear that electromagnetic waves are characterized by some properties that were previously attributed to material particles, corpuscles.
This idea is called wave-particle duality.

Electromagnetic radiation exists exactly as long as our Universe lives. It played a key role in the evolution of life on Earth. In fact, this disturbance is the state of an electromagnetic field distributed in space.

Characteristics of electromagnetic radiation

Any electromagnetic wave is described using three characteristics.

1. Frequency.

2. Polarization.

Polarization– one of the main wave attributes. Describes the transverse anisotropy of electromagnetic waves. Radiation is considered polarized when all wave oscillations occur in the same plane.

This phenomenon is actively used in practice. For example, in cinemas when showing 3D films.

Using polarization, IMAX glasses separate the image that is intended for different eyes.

Frequency– the number of wave crests that pass by the observer (in this case, the detector) in one second. It is measured in Hertz.

Wavelength– a specific distance between the nearest points of electromagnetic radiation, the oscillations of which occur in the same phase.

Electromagnetic radiation can propagate in almost any medium: from dense matter to vacuum.

The speed of propagation in a vacuum is 300 thousand km per second.

Interesting video about the nature and properties of EM waves, see the video below:

Types of electromagnetic waves

All electromagnetic radiation is divided by frequency.

1. Radio waves. There are short, ultra-short, extra-long, long, medium.

The length of radio waves ranges from 10 km to 1 mm, and from 30 kHz to 300 GHz.

Their sources can be both human activity and various natural atmospheric phenomena.

2. . The wavelength ranges from 1mm to 780nm, and can reach up to 429 THz. Infrared radiation is also called thermal radiation. The basis of all life on our planet.

3. Visible light. Length 400 - 760/780 nm. Accordingly, it fluctuates between 790-385 THz. This includes the entire spectrum of radiation that can be seen by the human eye.

4. . The wavelength is shorter than that of infrared radiation.

Can reach up to 10 nm. such waves are very large - about 3x10^16 Hz.

5. X-rays. waves are 6x10^19 Hz, and the length is about 10 nm - 5 pm.

6. Gamma waves. This includes any radiation that is greater than X-rays, and the length is shorter. The source of such electromagnetic waves are cosmic, nuclear processes.

Scope of application

Somewhere since the end of the 19th century, all human progress has been associated with the practical use of electromagnetic waves.

The first thing worth mentioning is radio communication. It gave people the opportunity to communicate, even if they were far from each other.

Satellite broadcasting, telecommunications are further development primitive radio communications.

It is these technologies that have shaped the information image of modern society.

Sources of electromagnetic radiation should be considered both large industrial facilities and various power lines.

Electromagnetic waves are actively used in military affairs (radars, complex electrical devices). Also, medicine could not do without their use. Infrared radiation can be used to treat many diseases.

X-rays help determine damage to human internal tissues.

Lasers are used to perform a number of operations that require pinpoint precision.

The importance of electromagnetic radiation in human practical life is difficult to overestimate.

Soviet video about the electromagnetic field:

Possible negative impact on humans

Although useful, strong sources of electromagnetic radiation can cause symptoms such as:

Fatigue;

Headache;

Nausea.

Excessive exposure to certain types of waves causes damage internal organs, central nervous system, brain. Changes in the human psyche are possible.

An interesting video about the effect of EM waves on humans:

To avoid such consequences, almost all countries in the world have standards governing electromagnetic safety. Each type of radiation has its own regulatory documents (hygienic standards, radiation safety standards). The effect of electromagnetic waves on humans has not been fully studied, so WHO recommends minimizing their exposure.

), describing the electromagnetic field, theoretically showed that the electromagnetic field in a vacuum can exist in the absence of sources - charges and currents. A field without sources has the form of waves propagating at a finite speed, which in a vacuum is equal to the speed of light: With= 299792458±1.2 m/s. The coincidence of the speed of propagation of electromagnetic waves in vacuum with the previously measured speed of light allowed Maxwell to conclude that light is electromagnetic waves. A similar conclusion later formed the basis electromagnetic theory Sveta.

In 1888, the theory of electromagnetic waves received experimental confirmation in the experiments of G. Hertz. Using a high voltage source and vibrators (see Hertz vibrator), Hertz was able to perform subtle experiments to determine the speed of propagation of an electromagnetic wave and its length. It was experimentally confirmed that the speed of propagation of an electromagnetic wave is equal to the speed of light, which proved the electromagnetic nature of light.