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Electromagnetic radiation is a combination of oscillating electric and magnetic fields in perpendicular orientation to each other, moving through space, effectively transporting energy from one place to another. Visible light is a form of electromagnetic radiation. The physics of electromagnetic radiation is electrodynamics, a subfield of electromagnetism.Electromagnetic waves were predicted by Maxwell's equations and subsequently discovered by Heinrich Hertz.
Any electric charge which accelerates radiates electromagnetic radiation. Electromagnetic information about the charge travels at the speed of light. Accurate treatment thus incorporates a concept known as retarded time (as opposed to advanced time, which is unphysical in light of causality), which adds to the expressions for the electrodynamic electric field and magnetic field. These extra terms are responsible for electromagnetic radiation. When any wire (or other conducting object such as an antenna) conducts alternating current, electromagnetic radiation is propagated at the same frequency as the electric current. Depending on the circumstances, it may behave as waves or as particlesA particle is # In particle physics, a basic unit of matter or energy. In ecology, a small object of nonbiological kind. In linguistics, a grammatical particle. In computer graphics, an element of a particle system (simulation). In common use: a very smal. As a wave, it is characterized by a velocity (the speed of lightCherenkov effect in a "swimming pool" nuclear reactor. The effect is due to electrons moving faster than the speed at which light moves in water. The speed of light (denoted as c reputedly from the Latin celeritas "speed", and also known as Einstein's con), wavelengthThe wavelength is the distance between repeating units of a wave pattern. It is commonly designated by the greek letter lambda (λ). In a sine wave, the wavelength is the distance between peaks: The x axis represents distance, and I would be some va, and frequencyFrequency is the measurement of the number of times that a repeated event occurs per unit time. To calculate the frequency, one fixes a time interval, counts the number of occurrences of the event within that interval, and then divides this count by the l. When considered as particles, they are known as photonsFor the Japanese anime video, see Photon (anime). In physics, the photon (from Greek φοτος, meaning light is a quantum of excitation of the quantised electromagnetic field and is one of the elementary particles studied by qu, and each has an energy related to the frequency of the wave given by Planck'sMax Karl Ernst Ludwig Planck ( April 23, 1858 October 4, 1947) was a German physicist who is considered to be the inventor of quantum theory. Born in Kiel, Planck started his physics studies at Munich University in 1874, graduating in 1879 in Berlin. relation E = hν, where E is the energy of the photon, h = 6.626 × 10-34 J·s is Planck's constantPlanck's constant denoted h is a physical constant that is used to describe the sizes of quanta. It plays a central role in the theory of quantum mechanics, and is named after Max Planck, one of the founders of quantum theory. It has a value of approximat, and ν is the frequency of the wave.
Generally, electromagnetic radiation is classified by wavelength into radio, microwave, infrared light, visible light, ultraviolet light, X-rays and gamma rays. The details of this classification are contained in the article on the electromagnetic spectrum.
The effect of radiation depends on the amount of energy per quantum it carries. High energies correspond to high frequencies and short wavelengths, and vice versa. One rule is always obeyed, regardless of the circumstances. Radiation in vacuum always travels at the speed of light, relative to the observer, regardless of the observer's velocity. (This observation led to Albert Einstein's development of the theory of special relativity).
Much information about the physical properties of an object can be obtained from its electromagnetic spectrum; this can be either the spectrum of light emitted from, or transmitted through the object. This involves spectroscopy and is widely used in astrophysics. For example; many hydrogen atoms emit radio waves which have a wavelength of 21.12 cm.
When electromagnetic radiation impinges upon a conductor it induces an electric current flow on the surface of that conductor. This effect (the skin effect) is used in antennas. Electromagnetic radiation may also cause certain molecules to absorb energy and thus to heat up; this is exploited in microwave ovens.
