Source of EM wave
Electromagnetic waves are the combination of electric and
magnetic field waves produced by moving charges.
1. The creation of all electromagnetic waves
begins with a charged particle. This charged
particle creates an electric field. When it
accelerates, the charged particle creates
ripples, or oscillations, in its electric field,
and also produces a magnetic field (as
predicted by Maxwell's equations).
2. Once in motion, the electric and magnetic
fields created by a charged particle are self-
perpetuating. This means that an electric
field that oscillates as a function of time will
produce a magnetic field, and a magnetic
field that changes as a function of time will
produce an electric field.
3. Both electric and magnetic fields in an
electromagnetic wave will fluctuate in time,
one causing the other to change.
Properties[edit]
Electromagnetic waves can be imagined as a self-propagating
transverse oscillating wave of electric and magnetic fields. This 3D animation shows a plane linearly
polarized wave propagating from left to right. The electric and magnetic fields in such a wave are in-
phase with each other, reaching minima and maxima together.
, 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.[13] 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. [14]
The electromagnetic fields of light are not affected by traveling through static electric or magnetic
fields in a linear medium such as a vacuum. However, in nonlinear media, such as
some crystals, interactions can occur between light and static electric and magnetic fields—these
interactions include the Faraday effect and the Kerr effect.[15][16]
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. [17]
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.[18] Demonstrating that the light itself is quantized, not merely its interaction with
matter, is a more subtle affair.
Some experiments display both the wave and particle natures of electromagnetic waves, such as
the self-interference of a single photon.[19] When a single photon is sent through
an interferometer, it passes through both paths, interfering with itself, as waves do, yet is
detected by a photomultiplier or other sensitive detector only once.
A quantum theory of the interaction between electromagnetic radiation and matter such as
electrons is described by the theory of quantum electrodynamics.
Electromagnetic waves can be polarized, reflected, refracted, or diffracted, and can interfere with
each other.
Electromagnetic spectrum[edit]
Main article: Electromagnetic spectrum
Electromagnetic waves are the combination of electric and
magnetic field waves produced by moving charges.
1. The creation of all electromagnetic waves
begins with a charged particle. This charged
particle creates an electric field. When it
accelerates, the charged particle creates
ripples, or oscillations, in its electric field,
and also produces a magnetic field (as
predicted by Maxwell's equations).
2. Once in motion, the electric and magnetic
fields created by a charged particle are self-
perpetuating. This means that an electric
field that oscillates as a function of time will
produce a magnetic field, and a magnetic
field that changes as a function of time will
produce an electric field.
3. Both electric and magnetic fields in an
electromagnetic wave will fluctuate in time,
one causing the other to change.
Properties[edit]
Electromagnetic waves can be imagined as a self-propagating
transverse oscillating wave of electric and magnetic fields. This 3D animation shows a plane linearly
polarized wave propagating from left to right. The electric and magnetic fields in such a wave are in-
phase with each other, reaching minima and maxima together.
, 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.[13] 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. [14]
The electromagnetic fields of light are not affected by traveling through static electric or magnetic
fields in a linear medium such as a vacuum. However, in nonlinear media, such as
some crystals, interactions can occur between light and static electric and magnetic fields—these
interactions include the Faraday effect and the Kerr effect.[15][16]
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. [17]
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.[18] Demonstrating that the light itself is quantized, not merely its interaction with
matter, is a more subtle affair.
Some experiments display both the wave and particle natures of electromagnetic waves, such as
the self-interference of a single photon.[19] When a single photon is sent through
an interferometer, it passes through both paths, interfering with itself, as waves do, yet is
detected by a photomultiplier or other sensitive detector only once.
A quantum theory of the interaction between electromagnetic radiation and matter such as
electrons is described by the theory of quantum electrodynamics.
Electromagnetic waves can be polarized, reflected, refracted, or diffracted, and can interfere with
each other.
Electromagnetic spectrum[edit]
Main article: Electromagnetic spectrum
