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An electromagnetic field (also EM field) is a physical field, mathematical functions of position and time, representing the influences on and due to electric charges. [1] The field at any point in space and time can be regarded as a combination of an electric field and a magnetic field .
The density of the linear momentum of the electromagnetic field is S/c 2 where S is the magnitude of the Poynting vector and c is the speed of light in free space. The radiation pressure exerted by an electromagnetic wave on the surface of a target is given by = .
In physics, electromagnetic radiation (EMR) is the set of waves of an electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. [ 1 ] [ 2 ] Classically , electromagnetic radiation consists of electromagnetic waves , which are synchronized oscillations of electric and magnetic fields .
Representation of the electric field vector of a wave of circularly polarized electromagnetic radiation. The electromagnetic force is the second strongest of the four known fundamental forces and has unlimited range. [17] All other forces, known as non-fundamental forces. [18] (e.g., friction, contact forces) are derived from the four ...
A changing electromagnetic field propagates away from its origin in the form of a wave. These waves travel in vacuum at the speed of light and exist in a wide spectrum of wavelengths . Examples of the dynamic fields of electromagnetic radiation (in order of increasing frequency): radio waves , microwaves , light ( infrared , visible light and ...
Waves can be constructed as physical fields, due to their finite propagation speed and causal nature when a simplified physical model of an isolated closed system is set [clarification needed]. They are also subject to the inverse-square law. For electromagnetic waves, there are optical fields, and terms such as near- and far-field limits for ...
[25]: 696–700 These variations are an electromagnetic wave. Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell developed a set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current.
In electrodynamics, Poynting's theorem is a statement of conservation of energy for electromagnetic fields developed by British physicist John Henry Poynting. [1] It states that in a given volume, the stored energy changes at a rate given by the work done on the charges within the volume, minus the rate at which energy leaves the volume.