Electromagnetic waves (Table which will be given below) is a perturbation of the magnetic and electric fields are distributed in space.Their are several types.The study deals with the physics of these disturbances.Electromagnetic waves are produced due to the fact that the alternating electric field generates magnetic fields, and this in turn generates electrical.
History Research
first theory, which can be considered the oldest versions of the hypotheses about electromagnetic waves are at least to the time of Huygens.At that time, speculation reached expressed quantitative development.Huygens in 1678, the year has produced a kind of "outline" theory - "Treatise on the world".In 1690 he also published another wonderful work.It was presented the qualitative theory of reflection, refraction in the form in which it is today represented in school textbooks ("Electromagnetic waves", Grade 9).
Along with this was formulated Huygens' principle.With it, the opportunity to study the motion of the wave front.This principle later found its development in the works of Fresnel.Huygens-Fresnel principle has special significance in the theory of diffraction and the wave theory of light.
In 1660-1670 years of the great experimental and theoretical contributions were made in research Hooke and Newton.Who discovered the electromagnetic waves?What experiments were conducted to prove their existence?What are the types of electromagnetic waves?This was on.
Justification Maxwell
Before we talk about who discovered electromagnetic waves, it should be said that the first scientist who predicted their existence in general, has become Faraday.His hypothesis he put forward in 1832, the year.Construction of a theory later studied Maxwell.By 1865, the ninth year he completed this work.As a result, Maxwell strictly formalized mathematical theory, justifying the existence of the phenomena under consideration.He also was determined the velocity of propagation of electromagnetic waves coincide with applies if the value of the speed of light.This, in turn, allowed him to substantiate the hypothesis that light is a type of radiation considered.
Experimental observation
Maxwell's theory was confirmed in the experiments of Hertz in 1888.It should be said that the German physicist conducted his experiments to disprove the theory, despite its mathematical basis.However, thanks to his experiments Hertz was the first who discovered electromagnetic waves practically.In addition, in the course of their experiments, scientists have identified the properties and characteristics of radiations.
electromagnetic oscillations and waves Hertz received by the excitation pulse series of rapidly flow in the shaker with a source of high voltage.High-frequency currents can be detected by the circuit.Wherein the oscillation frequency is higher, the higher the capacitance and inductance.But at the same high frequency is no guarantee of high flow.To conduct their experiments Hertz used a relatively simple device, which is now called - "Hertz vibrator."The device is an open-type oscillation circuit.
Driving Experience Hertz
Register radiation was carried out by means of the receiving vibrator.This device had the same structure as that of the emitting device.Under the influence of the electromagnetic wave electrical alternating field in the receiver is excited current oscillations.If this device its natural frequency and the frequency of the stream match, then there is resonance.As a result of perturbations in the receiver with a greater amplitude occur.Researcher discovers them, watching the sparks between conductors in a small gap.
Thus, Hertz was the first who discovered electromagnetic waves has proved their ability to reflect well on the conductors.They were almost justified the formation of a standing light.Furthermore, Hertz determined speed of propagation of electromagnetic waves in air.
study of the characteristics of electromagnetic waves propagate in almost all environments.In the space that is filled with a material, the radiation can be distributed in many cases quite well.But they slightly change their behavior.
Electromagnetic waves in vacuum are determined without damping.They are distributed to any arbitrarily large distance.The main features include wave polarization, frequency and length.Description of the properties is carried out in the framework of electrodynamics.However, the radiation characteristics of some regions of the spectrum are engaged in more specific areas of physics.These include, for example, include optics.The study
hard electromagnetic radiation of short-wave spectral end of the section deals with high energy.Taking into account the dynamics of modern ideas ceased to be self-discipline and combined with the weak interactions in a single theory.
theories used in the study of the properties of
Today, there are various methods for facilitating the modeling and study of manifestations and properties of the vibrations.The most fundamental of proven and considered a complete theory of quantum electrodynamics.Therefrom by one or the other simplifications becomes possible to obtain the following methods, which are widely used in various fields.
Description relatively low-frequency radiation in the macroscopic environment is carried out by means of classical electrodynamics.It is based on Maxwell's equations.In the application, there are applications to simplify.When used optical studies of optics.Wave theory applicable in cases where some portion of the optical system size close to the wavelength.Quantum optics is used when the scattering processes are important, the absorption of photons.
geometric optical theory - the limiting case in which permitted neglecting wavelength.Also there are some applied and fundamental sections.These include, for example, include astrophysics, biology of vision and photosynthesis, photochemistry.How are classified electromagnetic waves?The table clearly shows the distribution into groups, is as follows.
Classification
existing frequency range of electromagnetic waves.Between them, there is no abrupt transitions, sometimes they overlap.The boundaries between them are rather relative.Due to the fact that the flow is distributed continuously, the frequency is rigidly associated with the length.Below are the ranges of electromagnetic waves.
| name | length | frequency |
| Gamma | Less than 5 pm | more than 6 • 1019 Hz |
| Roentgen | 10 nm- 5 pm | 3 • 1016-6 • 1019 Hz |
| Ultraviolet | 380 - 10 nm | 7,5 • 1014-3 • 1016 Hz |
| Visible radiation from 780 to 380 nm | 429-750 THz | |
| Infrared | 1 mm - 780 nm | 330 GHz-429 THz |
| ultrashort | 10 m - 1 mm | 30 MHz to 300 GHz |
| Short | 100 m - 10 m | 3-30 MHz |
| Average | 1 km - 100 m | 300 kHz-3 MHz |
| Long | 10 km - 1 km | 30-300 kHz |
| Extra long | More than 10 km | least 30 kHz |
Ultrashort light can be divided into micrometer (sub-millimeter), millimeter, centimeter, decimeter, meter.If the wavelength of the electromagnetic radiation is less than a meter, then its called oscillation of super high frequency (SHF).
Types of electromagnetic waves
above presented ranges of electromagnetic waves.What are the different kinds of flows?Group ionizing radiation comprises gamma and X-rays.It should be said that is able to ionize atoms and ultraviolet light, and even visible light.The boundaries, which are gamma and x-ray flux, defined very conditional.As a general orientation adopted beyond 20 eV - 0.1 MeV.Gamma flows in the narrow sense emitted kernel, X - e-atomic shell during ejection from the low-lying electron orbits.However, this classification does not apply to hard radiation generated without nuclei and atoms.
X-ray flux generated during deceleration of fast charged particles (protons, electrons, and others) and as a result of processes that occur inside the atomic electron shells.Gamma oscillations are the result of processes within the nuclei of atoms and elementary particles in the conversion.
radio flux
Due to the large lengths consideration of these waves may be carried out without taking into account the atomistic structure of the medium.As an exception to protrude only very short streams are adjacent to the infrared.In the radio properties of quantum oscillations appear quite weak.However, they should be considered, for example, in the analysis of molecular standards of frequency and time during the cooling apparatus to a temperature a few degrees Kelvin.
quantum properties are taken into account in the description of oscillators and amplifiers in the millimeter and centimeter ranges.It formed in the radio while driving AC conductors for the corresponding frequency.A passing electromagnetic wave in space excites an alternating current, corresponding to it.This property is used in the design of antennas in radio.
Visible flows
ultraviolet and infrared radiation is visible in the broad sense so called optical part of the spectrum.Isolation of the area is due not only to the proximity of the respective zones, and similar devices used in research and developed mainly in the study of visible light.These include, in particular, the mirrors and lenses for focusing the radiation, diffraction gratings, prisms and other.
frequencies of optical waves are comparable to those of molecules and atoms, and the length of them - with the intermolecular distances and molecular dimensions.Therefore essential in this field are phenomena that are caused by the atomic structure of the substance.For the same reason, the light with the wave possesses quantum properties.
emergence of optical flow
most famous source is the sun.The surface of the star (the photosphere) has a temperature of 6000 ° Kelvin emits bright white light.The highest value of the continuous spectrum is located in the "green" zone - 550 nm.There is a maximum visual sensitivity.Fluctuations in the optical range occur when heated bodies.Infrared flows therefore also referred to as heat.
stronger heats the body, the higher the frequency, which is the maximum range.At a certain temperature rises observed incandescence (glow in the visible range).When this occurs, first red, then yellow and more.Creation and registration of optical flow may occur in biological and chemical reactions, one of which is used in photography.For most creatures living on earth as an energy source performs photosynthesis.This biological reaction occurs in plants exposed optical solar radiation.
Features electromagnetic waves
properties of the medium and a source of influence on the flow characteristics.So it mounted, in particular the time dependence of the fields, which identifies the type of stream.For example, when the distance from the vibrator (increasing) the radius of curvature becomes greater.The result is a plane electromagnetic wave.The interaction also occurs with matter in different ways.The absorption and emission flow can usually be described using classical electrodynamic ratios.For waves of the optical field and the more hard rays should take into account their quantum nature.
stream source
Despite the physical differences, everywhere - in radioactive substances, television transmitters, an incandescent bulb - the electromagnetic waves excited by the electrical charges that are moving with acceleration.There are two basic types of sources: microscopic and macroscopic.At first there is an abrupt transition of charged particles from one to another level within the molecules or atoms.
Microscopic sources emit X-ray, gamma, ultraviolet, infrared, visible, and in some cases, long-wave radiation.As an example of the latter is the line of the hydrogen spectrum, which corresponds to a wave of 21 cm. This phenomenon is particularly important in astronomy.
sources macroscopic type are radiators in which free electrons of conductors make periodic synchronous oscillations.In systems of this category are generated flows from the millimeter to the longest (in power lines).
structure and the power flows
electrical charges moving with acceleration and periodically changing currents affect each other with certain forces.The direction and magnitude are dependent on such factors as the size and configuration of the field, which contains the currents and charges, their relative magnitude and direction.Significant influence and electrical characteristics of your environment, as well as changes in the concentration of charge and current distribution source.
Due to the complexity of the general statement of the problem to submit the law of force in a single formula can not.The structure, called the electromagnetic field and considered, if necessary, as a mathematical object, determined by the distribution of charges and currents.It, in turn, creates a given source, taking into account boundary conditions.Terms and conditions determined by the shape and characteristics of the zone of interaction of the material.If it is carried out on the infinite space, supplemented by the aforementioned circumstances.As a special additional condition in such cases acts as a condition of radiation.Through it guaranteed the "right" behavior of the field at infinity.
Chronology study
corpuscle-kinetic theory University in some of their positions anticipating some postulates of the theory of electromagnetic field, "revolving" (rotational) motion of particles, "zyblyuschayasya" (wave) theory of light, its commonality with the nature of electricity and so on. D.Infrared flows were discovered in 1800 by Herschel (British scientist), and in the next, 1801 m, Ritter described ultraviolet.Radiation shorter than ultraviolet, Roentgen range was opened in 1895, the year on November 8.Subsequently, it became known as the X-ray.
electromagnetic waves has been studied by many scientists.However, the first to explore the possibilities of flows, their scope has become Narkevitch-Iodko (Belarusian scientific figure).He studied the properties of the flow in relation to the practice of medicine.Gamma radiation was discovered by Paul Villard in 1900.At the same time Planck held theoretical studies of the properties of a blackbody.During the study they were open quantum process.His work was the beginning of the development of quantum physics.It was subsequently published several works of Einstein and Planck.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 currents.Its development continued in the works of the leading scientific figures of the twentieth century.
Further research and work on the quantum theory of electromagnetic radiation and its interaction with matter eventually 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
value of physics in the modern world is large enough.Almost everything that is used today in human life, appeared thanks to the practical use of research of great scientists.
