Radiation electromagnetic

.James Clerk Maxwell nwetara ụdị ebili mmiri nke nha eletrik na magnetik, si otú a na-ekpughe ọdịdị ebili mmiri nke ọkụ eletrik na magnetik na ihe ngosi ha.  N'ihi na ọsọ nke ebili mmiri EM buru amụma site na nha nha ebili mmiri dabara na ọsọ ọkụ a tụrụ atụ, Maxwell kwubiri na ìhè n'onwe ya bụ EM wave.[1][2]  Heinrich Hertz kwadoro nhata Maxwell site na nnwale na ebili mmiri redio

Nha nhata Maxwell kwadoro na ụfọdụ ụgwọ na iyi ("isi mmalite") na-emepụta ụdị oghere electromagnetic dị n'akụkụ ha nke na-adịghị enwu.  Ugbu a na-emepụta oghere magnetik ozugbo, mana ọ bụ ụdị dipole magnetik na-anwụ n'ebe dị anya site na nke ugbu a.  N'otu aka ahụ, ụgwọ na-ebugharị na-ebugharị na onye na-eduzi site na ike eletrik na-agbanwe agbanwe (dịka na antenna) na-emepụta ụdị eletriki eletrik dipole, mana nke a na-agbadakwa na anya.  Ogige ndị a mebere mpaghara nso nso isi iyi EMR.  Ọnweghị àgwà ndị a na-ahụ maka radieshon EM.  Kama nke ahụ, ha na-ebute omume ikuku electromagnetic nke na-ebufe ike nke ọma na onye nnata dị nso na isi iyi, dị ka induction magnet n'ime ihe ntụgharị.  Dịka, mpaghara dị nso na-enwe mmetụta dị ike na isi mmalite nke aka ha, na-eme ka "ibu" na-abawanye (mbelata reactance eletrik) na isi iyi ma ọ bụ transmitter, mgbe ọ bụla onye na-anata na-ewepụ ike n'ọhịa EM.  Ma ọ bụghị ya, ndị a ubi adịghị "na-agbasa" kpam kpam pụọ n'ime ohere, na-ebu ha ume pụọ na-enweghị anya-oke, kama oscillate, na-eweghachi ha ume na transmitter ma ọ bụrụ na ọ bụghị natara site na nnata.[citation needed]

N'ụzọ dị iche, EM n'ebe dị anya mejupụtara radieshon nke na-enweghị onye na-ebufe ya n'echiche na (n'adịghị ka ọ dị na ihe ntụgharị ọkụ eletrik) onye na-ebugharị na-achọ otu ike iji zipu mgbanwe ndị a n'ubi, ma ọ bụ akara ngosi.  eburu ozugbo ma ọ bụ na ọ bụghị.  Akụkụ a dị anya nke oghere electromagnetic bụ "ụzarị ọkụ eletrik" (nke a na-akpọkwa ebe dị anya).  Ebe ndị dị anya na-agbasa (radiate) na-ahapụghị ka onye na-ebugharị ya metụta ha.  Nke a na-eme ka ha nwee onwe ha n'echiche na ịdị adị ha na ike ha, mgbe ha hapụsịrị onye na-ebufe ya, na-enwere onwe ya kpam kpam na onye na-ebufe na onye nnata.  N'ihi nchekwa nke ike, oke ike na-agafe n'elu okirikiri ọ bụla nke agbadoro gburugburu isi iyi bụ otu.  N'ihi na elu dị otú ahụ nwere ebe nhata na square nke anya site na isi iyi, ike njupụta nke EM radieshon si isotropic isi iyi mbelata na inverse square nke anya site na isi iyi;  nke a ka a na-akpọ iwu inverse-square.  Nke a dị iche na akụkụ dipole nke ubi EM dị nso na isi iyi (nke dị nso), nke na-adịgasị iche n'ịdị ike dịka iwu ike cube siri dị, ma si otú a anaghị ebufe ike echekwara n'ebe dị anya, kama kama ịdaba.  na anya, na ike ya (dị ka e kwuru) na-alaghachi ngwa ngwa na transmitter ma ọ bụ na-etinye uche ya site na nnata dị nso (dị ka eriri igwe nke abụọ nke transformer).

Na Liénard-Wiechert nwere ike imepụta oghere eletrik na magnetik n'ihi mmegharị nke otu akụkụ (dị ka nhata Maxwell si kwuo), okwu ndị metụtara ngwangwa nke urughuru bụ ndị na-ahụ maka akụkụ nke ubi a na-ewere dị ka radieshon electromagnetic. N'ụzọ dị iche, okwu metụtara na mgbanwe static eletriki nke urughuru na okwu magnetik nke na-esi na urughuru si otu ọsọ ọsọ, jikọtara abụọ na electromagnetic nso-ubi, na anaghị agụnye EM radieshon. [ a chọrọ nkọwa ]

Electric and magnetic fields obey the properties of superposition. Thus, a field due to any particular particle or time-varying electric or magnetic field contributes to the fields present in the same space due to other causes. Further, as they are vector fields, all magnetic and electric field vectors add together according to vector addition. For example, in optics two or more coherent light waves may interact and by constructive or destructive interference yield a resultant irradiance deviating from the sum of the component irradiances of the individual light waves.

In refraction, a wave crossing from one medium to another of different density alters its speed and direction upon entering the new medium. The ratio of the refractive indices of the media determines the degree of refraction, and is summarized by Snell's law. Light of composite wavelengths (natural sunlight) disperses into a visible spectrum passing through a prism, because of the wavelength-dependent refractive index of the prism material (dispersion); that is, each component wave within the composite light is bent a different amount.

EM radiation exhibits both wave properties and particle properties at the same time (see wave-particle duality). Both wave and particle characteristics have been confirmed in many experiments. Wave characteristics are more apparent when EM radiation is measured over relatively large timescales and over large distances while particle characteristics are more evident when measuring small timescales and distances. For example, when electromagnetic radiation is absorbed by matter, particle-like properties will be more obvious when the average number of photons in the cube of the relevant wavelength is much smaller than 1. It is not so difficult to experimentally observe non-uniform deposition of energy when light is absorbed, however this alone is not evidence of "particulate" behavior. Rather, it reflects the quantum nature of matter. Demonstrating that the light itself is quantized, not merely its interaction with matter, is a more subtle affair.