In 1865, the famous English physicist John. Maxwell, based on the results of work on the study of Faraday's electromagnetic field, could theoretically justify the possibility of the existence of such fields in the absence of currents and charges, their breed.Configuration field is the source of a wave.By studying the properties of electromagnetic waves, it is impossible not to notice an interesting fact: the propagation velocity depends on the environment.For example, in a vacuum, it is about 300 thousand. Km / s.Since this value corresponds to the speed of light, it is giving Maxwell assume that the light is a form of electromagnetic waves.Later it was confirmed by experiments of Hertz.Before the advent of Maxwell's theory was believed that the visible light, X-rays, ultraviolet, radio are not related to radiation.In fact, the properties depend on the wave length.The whole range was conditionally divided into regions, each with its own characteristic symptoms.
unique properties of electromagnetic waves, as their total interaction with matter is explained by two components - electric and magnetic.Thus, in the electromagnetic wave, which is no external influence, both fields vary in their directions and planes being perpendicular to the propagation direction of the wave.The basic properties of electromagnetic waves presents a variety of manifestations, regardless of the nature of the source.Consider some of them.It is much more convenient to represent real-world experience, so mentally we use two devices - a generator of radio waves directed radiation and the receiver.As already indicated, the results are applicable to all types of waves.Knowing the properties of electromagnetic waves that can be manipulated in a desired manner.
In daily life, each of us faces every day with reflection.For example, sometimes, to the mobile phone lost communication with the base station, just go into the room with thick concrete walls, or even in an ordinary house elevator.Returning to the experiment, if the transmitter and receiver positioned at an angle to each other, then the signal will not be registered (emitter directional).But it is necessary to place at the intersection of two conventional lines (direction vector) of the metal plate, the receiver will catch the light, that is, there is a reflection.Similar properties of electromagnetic waves are formulated in the statement of the equality of the angles of incidence and reflection.
next property - is the refraction.When the location of the receiver and the transmitter aimed at different altitudes, the signal will not be caught.But if you put in between paraffin cube, the whole scheme works.This occurs due to change in the direction of wave propagation at the interface between two dielectric media (air and paraffin).
Further worth mentioning interference.If the two metal plates are arranged in close proximity to one another, forming an angle slightly smaller than 180 degrees, then the radiation radio wave on the receiver sheet will catch the difference in intensity depending on the placement of its relatively sheets.Well-known example - the satellite dish.It is the "saucer" amplifies the signal by collecting the scattered wave and concentrating them on the receiver.
Another known property - diffraction.Partly thanks to it manages to use the radio.Experience in the following: between the generator and the receiver put the metal plate, and the distance between them - is minimal.As a result, no signal, as reflected from the back plate, toward the generator.But if spread to the sides of the plate and the receiver oscillator, the signal appears.This happens due to the properties of the waves bend around obstacles.