Electromagnetic radiation , waves produced by the oscillation or acceleration of an electric charge . Electromagnetic waves have electrical and magnetic components. Electromagnetic radiation can be arranged in a spectrum that ranges from very high frequency waves (small wavelengths) to very low frequencies ( high wavelengths ). Visible light is only a small part of the electromagnetic spectrum. In decreasing order of frequencies (or increasing wavelengths), the electromagnetic spectrum is composed of gamma rays, hard and soft X- rays, ultraviolet radiation , visible light ,infrared rays , microwaves and radio waves. Gamma rays and hard X-rays have a wavelength of between 0.005 and 0.5 nanometers (a nanometer, or nm, is a millionth of a millimeter). Soft X-rays overlap with ultraviolet radiation at wavelengths close to 50nm. The ultraviolet region, in turn, gives way to visible light, which ranges from approximately 400 to 800 nm. Infrared rays or ‘heat radiation’ (see Heat transfer) overlap with microwave radio frequencies, between 100,000 and 400,000 nm. From this wavelength to about 15,000 m, the spectrum is occupied by the different radio waves; beyond the radio zone, the spectrum enters the low frequencies, the wavelengths of which are measured in tens of thousands of kilometers.
Summary
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- 1 Properties
- 2 Theory
- 3 How many radiation
- 4 Sources
Properties
Electromagnetic waves do not need a material medium to propagate. Thus, these waves can traverse interplanetary and interstellar space and reach Earth from the Sun and stars. Regardless of their frequency and wavelength, all electromagnetic waves move in a vacuum at a speed c = 299,792 km / s. All radiation in the electromagnetic spectrum has the typical properties of wave motion , such as diffractionand interference. Wavelengths range from trillions of a meter to many kilometers. The wavelength (λ) and the frequency (f) of electromagnetic waves, related by the expression λ • f = c, are important in determining their energy, their visibility, their power of penetration and other characteristics.
Theory
British physicist James Clerk Maxwell established the theory of electromagnetic waves in a series of articles published in the 1860s. Maxwell mathematically analyzed the theory of electromagnetic fields and claimed that visible light was an electromagnetic wave. Physicists have known since the early 1800s that light propagates as a transverse wave (a wave in which vibrations are perpendicular to the forward direction of the wavefront). However, they assumed that light waves required some material medium to transmit, so they postulated the existence of a diffuse substance, called ether., which was the unobservable medium. Maxwell’s theory made that assumption unnecessary, but the concept of ether was not immediately abandoned, because it fitted in with the Newtonian concept of an absolute frame of space-time reference. A famous experiment carried out by the American physicist Albert Abraham Michelson and the chemist of the same nationality Edward Williams Morley in the late nineteenth century undermined the concept of the ether, and was very important in the development of the theory of relativity . From this work he concluded that the speed of electromagnetic radiation in a vacuum is an invariant quantity, which does not depend on the speed of the radiation source or the observer.
How many radiation
However, in the early 20th century physicists realized that wave theory did not explain all the properties of radiation . In 1900 , German physicist Max Planck demonstrated that radiation emission and absorption occurs in finite units of energy called ‘quanta’. In 1904 , Albert Einstein managed to explain some surprising experimental results regarding the external photoelectric effect, postulating that electromagnetic radiation can behave like a jet of particles. There are other phenomena of the interaction between radiation and matter that only the quantum theoryExplain. Thus modern physicists were forced to recognize that electromagnetic radiation sometimes behaves like particles and sometimes like waves. The parallel concept that implies that matter can also have undulatory as well as corpuscular characteristics was developed in 1925 by the French physicist Louis de Broglie .
