Electromagnetic radiation

electromagnetic waveelectromagnetic waveselectromagneticradiationEM radiationlightelectromagnetic emissionselectromagnetic signalnear fieldEM
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy.wikipedia
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Photon

photonslight quantaincident photon
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy. In quantum mechanics, an alternate way of viewing EMR is that it consists of photons, uncharged elementary particles with zero rest mass which are the quanta of the electromagnetic force, responsible for all electromagnetic interactions.
It is the quantum of the electromagnetic field including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force (even when static via virtual particles).

Microwave

microwavesmicrowave radiationmicrowave tube
It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
Microwaves are a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter; with frequencies between 300 MHz and 300 GHz.

Radio wave

radio wavesradioradio signal
It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light.

Infrared

IRnear-infraredinfra-red
It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
Infrared radiation (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light.

Radiant energy

electromagnetic energylight energyradiation
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy.
In physics, and in particular as measured by radiometry, radiant energy is the energy of electromagnetic and gravitational radiation.

Electromagnetic spectrum

spectrumspectraspectral
The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength.
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.

Speed of light

clight speedspeed of light in vacuum
In a vacuum electromagnetic waves travel at the speed of light, commonly denoted c.
Though this speed is most commonly associated with light, it is also the speed at which all massless particles and field perturbations travel in vacuum, including electromagnetic radiation and gravitational waves.

Quantum

quantaquantizedquantal
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy. In quantum mechanics, an alternate way of viewing EMR is that it consists of photons, uncharged elementary particles with zero rest mass which are the quanta of the electromagnetic force, responsible for all electromagnetic interactions.
For example, a photon is a single quantum of light (or of any other form of electromagnetic radiation).

Visible spectrum

visiblevisible lightspectrum
In order of increasing frequency and decreasing wavelength these are: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
Electromagnetic radiation in this range of wavelengths is called visible light or simply light.

Near and far field

far fieldnear fieldfar-field
Thus, EMR is sometimes referred to as the far field.
Non-radiative 'near-field' behaviors dominate close to the antenna or scattering object, while electromagnetic radiation 'far-field' behaviors dominate at greater distances.

Black-body radiation

blackbody radiationblack body spectrumblackbody spectrum
Quantum effects provide additional sources of EMR, such as the transition of electrons to lower energy levels in an atom and black-body radiation.
Black-body radiation is the thermal electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body).

Electromagnetic field

electromagnetic fieldselectromagneticEMF
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy.
Although modern quantum optics tells us that there also is a semi-classical explanation of the photoelectric effect—the emission of electrons from metallic surfaces subjected to electromagnetic radiation—the photon was historically (although not strictly necessarily) used to explain certain observations.

Non-ionizing radiation

non-ionizingnon-ionising radiationnonionizing radiation
EMR of visible or lower frequencies (i.e., visible light, infrared, microwaves, and radio waves) is called non-ionizing radiation, because its photons do not individually have enough energy to ionize atoms or molecules or break chemical bonds.
Non-ionizing (or non-ionising) radiation refers to any type of electromagnetic radiation that does not carry enough energy per quantum (photon energy) to ionize atoms or molecules—that is, to completely remove an electron from an atom or molecule.

Wavelength

wavelengthswave lengthsubwavelength
The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength.
A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary.

James Clerk Maxwell

MaxwellJ. C. MaxwellJames Maxwell
James Clerk Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields and their symmetry.
His most notable achievement was to formulate the classical theory of electromagnetic radiation, bringing together for the first time electricity, magnetism, and light as different manifestations of the same phenomenon.

Ionizing radiation

ionising radiationradiationnuclear radiation
In contrast, high frequency ultraviolet, X-rays and gamma rays are called ionizing radiation, since individual photons of such high frequency have enough energy to ionize molecules or break chemical bonds.
Ionizing radiation is made up of energetic subatomic particles, ions or atoms moving at high speeds (usually greater than 1% of the speed of light), and electromagnetic waves on the high-energy end of the electromagnetic spectrum.

Electromagnetic wave equation

electric fieldsequationsmultipole radiation fields
James Clerk Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields and their symmetry.
The electromagnetic wave equation is a second-order partial differential equation that describes the propagation of electromagnetic waves through a medium or in a vacuum.

Heinrich Hertz

Heinrich Rudolf HertzHertzHeinrich Rudolph Hertz
Maxwell's equations were confirmed by Heinrich Hertz through experiments with radio waves.
Heinrich Rudolf Hertz ( 22 February 1857 – 1 January 1894) was a German physicist who first conclusively proved the existence of the electromagnetic waves predicted by James Clerk Maxwell's equations of electromagnetism.

Elementary particle

elementary particlesparticleparticles
In quantum mechanics, an alternate way of viewing EMR is that it consists of photons, uncharged elementary particles with zero rest mass which are the quanta of the electromagnetic force, responsible for all electromagnetic interactions.
Subatomic constituents of the atom were identified in the early 1930s; the electron and the proton, along with the photon, the particle of electromagnetic radiation.

Ionization

ionizedionizeionisation
EMR of visible or lower frequencies (i.e., visible light, infrared, microwaves, and radio waves) is called non-ionizing radiation, because its photons do not individually have enough energy to ionize atoms or molecules or break chemical bonds. In contrast, high frequency ultraviolet, X-rays and gamma rays are called ionizing radiation, since individual photons of such high frequency have enough energy to ionize molecules or break chemical bonds.
Ionization can result from the loss of an electron after collisions with subatomic particles, collisions with other atoms, molecules and ions, or through the interaction with electromagnetic radiation.

Quantum mechanics

quantum physicsquantum mechanicalquantum theory
In quantum mechanics, an alternate way of viewing EMR is that it consists of photons, uncharged elementary particles with zero rest mass which are the quanta of the electromagnetic force, responsible for all electromagnetic interactions.
Around 1900–1910, the atomic theory but not the corpuscular theory of light first came to be widely accepted as scientific fact; these latter theories can be viewed as quantum theories of matter and electromagnetic radiation, respectively.

Planck constant

Planck's constantreduced Planck constantreduced Planck's constant
This relationship is given by Planck's equation E = hν, where E is the energy per photon, ν is the frequency of the photon, and h is Planck's constant.
He assumed that a hypothetical electrically charged oscillator in a cavity that contained black-body radiation could only change its energy in a minimal increment, E, that was proportional to the frequency of its associated electromagnetic wave.

Maxwell's equations

Maxwell equationsMaxwell equationMaxwell’s equations
According to Maxwell's equations, a spatially varying electric field is always associated with a magnetic field that changes over time.
Known as electromagnetic radiation, these waves may occur at various wavelengths to produce a spectrum of light from radio waves to γ-rays.

Atomic electron transition

electron transitiontransitionquantum jumps
Quantum effects provide additional sources of EMR, such as the transition of electrons to lower energy levels in an atom and black-body radiation.
Electron transitions cause the emission or absorption of electromagnetic radiation in the form of quantized units called photons.

Electromagnetism

electromagneticelectrodynamicselectromagnetic force
In quantum mechanics, an alternate way of viewing EMR is that it consists of photons, uncharged elementary particles with zero rest mass which are the quanta of the electromagnetic force, responsible for all electromagnetic interactions.
The electromagnetic force is carried by electromagnetic fields composed of electric fields and magnetic fields, and it is responsible for electromagnetic radiation such as light.