Relationship between photons and electromagnetic radiation

"The photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the. The electromagnetic (EM) spectrum is the range of all types of EM radiation. In space, infrared light helps us map the dust between stars. more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and . So far as I know, please correct me, photons have no electrical charge nor are relation between the classical and quantum views of electromagnetic waves.

This field satisfies a wave equation traveling at the speed of light.

What is the relation between electromagnetic wave and photon? - Physics Stack Exchange

Hence, light is an electromagnetic wave. Light consists of photons; and thus each photon carries a unit of energy. This behavior is demonstrated by the photoelectric and Compton effects. Since light is an electromagnetic energy, photons must also carry electromagnetic field and a unit of it. While photons are quantum objects, light still governed by Maxwell's classical theory.

The photon model is not critically consistent with Maxwell equations, since it has a dual nature. In fact light as a wave is well described by Maxwell.

Recall that Maxwell's equations don't involve the Planck's constant, and thus can not describe the particle nature of the photon. A complete Maxwell's equations should involve this missing element.

In quantum electrodynamic paradigm, the photon is brought to interact with the electrons by invoking the idea of minimal coupling where electrons and photons exchange momentum. The photon appears as a mediator between charged particles. At the same time while a moving charged particle has its self electric field, and magnetic field that depend on the particle velocity, the photon, the carrier of the electromagnetic energy is void of these self-fields because it has no charge and mass.

Thus, a charge-less photon can't have electric and magnetic fields accompanying its motion. The appropriate Maxwell's equations should then incorporate the photon linear momentum as well as its angular momentum. In such a case the new Maxwell's equations can then describe the dual nature of the photon. Like electric charge, the angular momentum is generally a conserved quantity. This distant part of the electromagnetic field is "electromagnetic radiation" also called the far-field.

The far-fields propagate radiate without allowing the transmitter to affect them. This causes them to be independent in the sense that their existence and their energy, after they have left the transmitter, is completely independent of both transmitter and receiver.

Due to conservation of energythe amount of power passing through any spherical surface drawn around the source is the same.

Because such a surface has an area proportional to the square of its distance from the source, the power density of EM radiation always decreases with the inverse square of distance from the source; this is called the inverse-square law. This is in contrast to dipole parts of the EM field close to the source the near-fieldwhich varies in power according to an inverse cube power law, and thus does not transport a conserved amount of energy over distances, but instead fades with distance, with its energy as noted rapidly returning to the transmitter or absorbed by a nearby receiver such as a transformer secondary coil.

Whereas the magnetic part of the near-field is due to currents in the source, the magnetic field in EMR is due only to the local change in the electric field.

In a similar way, while the electric field in the near-field is due directly to the charges and charge-separation in the source, the electric field in EMR is due to a change in the local magnetic field. Both processes for producing electric and magnetic EMR fields have a different dependence on distance than do near-field dipole electric and magnetic fields. Now independent of the source charges, the EM field, as it moves farther away, is dependent only upon the accelerations of the charges that produced it.

It no longer has a strong connection to the direct fields of the charges, or to the velocity of the charges currents. By contrast, the term associated with the changing static electric field of the particle and the magnetic term that results from the particle's uniform velocity, are both associated with the electromagnetic near-field, and do not comprise EM radiation.

This 3D animation shows a plane linearly polarized wave propagating from left to right. Note that the electric and magnetic fields in such a wave are in-phase with each other, reaching minima and maxima together.

Electrodynamics is the physics of electromagnetic radiation, and electromagnetism is the physical phenomenon associated with the theory of electrodynamics. 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. However, in nonlinear media, such as some crystalsinteractions can occur between light and static electric and magnetic fields — these interactions include the Faraday effect and the Kerr effect.

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.

Both wave and particle characteristics have been confirmed in many experiments.

Electromagnetic Spectrum Explained - Gamma X rays Microwaves Infrared Radio Waves UV Visble Light

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 too 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. Some experiments display both the wave and particle natures of electromagnetic waves, such as the self-interference of a single photon.

A quantum theory of the interaction between electromagnetic radiation and matter such as electrons is described by the theory of quantum electrodynamics.