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Does a Photon Exist

Yesterday, 3/8, I posted about electromagnetic waves. An excerpt:

Electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light, which, in a vacuum, is commonly denoted c (that is fast as EM fields can be). In homogeneous, isotropic media, the oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation, forming a transverse wave.
Simple explanation: EM radiation is synchronized electromagnetic fields that propagate at the speed of light.

From an online reference about polarization:

Light is an electromagnetic wave, and the electric field of this wave oscillates perpendicularly to the direction of propagation. Light is called unpolarized if the direction of this electric field fluctuates randomly in time.
If the direction of the electric field of light is well defined, it is called polarized light. The most common source of polarized light is a laser. In order to select a specific polarization of light, polarizers are used. By placing a linear polarizer over the light source, the lens, or both, it is possible to eliminate glare and hot spots from reflective objects or bring out surface defects. '

Synchrotron radiation is often observed in the universe. The two common scenarios are 1) high velocity electrons being accelerated radially by a magnetic field, or 2) an electric current being bent by a magnetic field.
Synchrotron radiation  covers a wide spectrum from infrared, to radio, to light, to X-ray.
the synchronized electromagnetic fields in the radiation originate in these electric and magnetic fields.

I have heard it described that light is always a wave (frequency) but under certain conditions it will seem a particle, called a photon. In the double slit experiment, you see interference patterns from a wave but you might detect what seem to be particles.
Here is wikipedia's description of a photon
The photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles). The photon has zero rest mass and always moves at the speed of light within a vacuum.

Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, exhibiting properties of both waves and particles. For example, a single photon may be refracted by a lens and exhibit wave interference with itself, and it can behave as a particle with definite and finite measurable position or momentum, though not both at the same time as per the Heisenberg's uncertainty principle. The photon's wave and quantum qualities are two observable aspects of a single phenomenon cannot be described by any mechanical model; a representation of this dual property of light that assumes certain points on the wavefront to be the seat of the energy is not possible. The quanta in a light wave are not spatially localized.

A photon is a massless particle defined by quantum physicists to replace the synchronized electromagnetic fields, and to address the observed particle/wave duality.

The photon is a subatomic particle that can exhibit wave behaviors. How this particle is created is unclear. It appears at the instant the light appears.
With electromagnetic radiation a photon as a particle would start at rest, then accelerate up to exactly the speed of light but it can never be observed before it attains c.

Polarization is handled like this:
Photon polarization is the quantum mechanical description of the classical polarized sinusoidal plane electromagnetic wave. An individual photon can be described as having right or left circular polarization, or a superposition of the two. Equivalently, a photon can be described as having horizontal or vertical linear polarization, or a superposition of the two.

The description of photon polarization contains many of the physical concepts and much of the mathematical machinery of more involved quantum descriptions, such as the quantum mechanics of an electron in a potential well. Polarization is an example of a qubit degree of freedom, which forms a fundamental basis for an understanding of more complicated quantum phenomena.

Is a photon an actual massless particle or is a photon just a concept developed by quantum physicists to describe electromagnetic radiation using the definitions common among subatomic particles?

Is a photon real?

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