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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 .
In physics, and in particular as measured by radiometry, radiant energy is the energy of electromagnetic [1] and gravitational radiation. As energy, its SI unit is the joule (J). The quantity of radiant energy may be calculated by integrating radiant flux (or power ) with respect to time .
Nonlinear dynamics can occur when electromagnetic fields couple to matter that follows nonlinear dynamical laws. [29] This is studied, for example, in the subject of magnetohydrodynamics, which combines Maxwell theory with the Navier–Stokes equations. [30] Another branch of electromagnetism dealing with nonlinearity is nonlinear optics.
A diagram of the electromagnetic spectrum, showing various properties across the range of frequencies and wavelengths. The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band.
Inductance — The phenomenon whereby the property of a circuit by which energy is stored in the form of an electromagnetic field. Induction heating — Heat produced in a conductor when eddy currents pass through it. Joule heating — Heat produced in a conductor when charges move through it, such as in resistors and wires.
An overview of absorption of electromagnetic radiation.This example shows the general principle using visible light as a specific example. A white light source—emitting light of multiple wavelengths—is focused on a sample (the pairs of complementary colors are indicated by the yellow dotted lines).
The electromagnetic field is described by classical electrodynamics, an example of a classical field theory. This theory describes many macroscopic physical phenomena accurately. [ 6 ] However, it was unable to explain the photoelectric effect and atomic absorption spectroscopy , experiments at the atomic scale.
The existence of electromagnetic radiation was proved by Heinrich Hertz in a series of experiments ranging from 1886 to 1889 in which he discovered the existence of radio waves. The full electromagnetic spectrum (in order of increasing frequency) consists of radio waves, microwaves , infrared radiation , visible light , ultraviolet light , X ...