What is the Difference Between Photon and Quantum?

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The main difference between a photon and a quantum lies in their definitions and the objects they represent.

  • Photon: A photon is the tiniest possible particle of light, also referred to as a quantum of light. It is the smallest conceivable particle of light in nature. In summary, a photon is a quantum, specifically a quantum of electromagnetic energy.
  • Quantum: A quantum is a discrete packet containing energy. It is the tiniest possible particle of any substance at the quantum level. Some other types of quanta include electrons, neutrinos, and the Higgs boson. In summary, a quantum is a general term for the smallest possible particle of any substance, while a photon is a specific type of quantum that represents light.

Both photons and quanta are crucial notions in current physics, with applications in various domains such as quantum physics, quantum chemistry, electromagnetic theory, optics, particle physics, and more. The terms "photon" and "quantum" are used interchangeably in some contexts, but they have distinct meanings and should not be misconstrued.

Comparative Table: Photon vs Quantum

The main difference between a photon and a quantum lies in their definitions and the context in which they are used. Here is a table summarizing their differences:

Photon Quantum
A photon is a quantum of electromagnetic energy, such as light. A quantum is a general term for a finite quantity of energy or a particle that makes up a whole.
Photons are specific particles that transmit light and have energy values expressed in eV (electronvolt) and J (joule). Quanta is a broader term used in quantum mechanics, referring to the mechanisms behind very small objects.
All photons are quantum, but not all quanta are photons. A quantum can refer to any small, discrete unit of energy or matter, not just electromagnetic energy.

In summary, a photon is a specific type of quantum that represents a quantum of electromagnetic energy, while a quantum is a more general term referring to any finite quantity of energy or a particle that makes up a whole.