What is a photon in terms of EM waves?

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SUMMARY

A photon is defined as the smallest excitation of the quantized electromagnetic field, fundamentally differing from classical electromagnetic (EM) waves. It is incorrect to equate a photon with one wavelength of an EM wave, as photons do not have a classical analog. Quantum electrodynamics (QED) provides a comprehensive framework for understanding photons, surpassing classical electrodynamics in scope. Coherent quantum states serve as the quantum analogs of classical EM waves, emphasizing the distinction between these two concepts.

PREREQUISITES
  • Quantum electrodynamics (QED)
  • Classical electromagnetic theory
  • Coherent quantum states
  • Understanding of quantized fields
NEXT STEPS
  • Study the principles of Quantum Electrodynamics (QED)
  • Explore the concept of coherent states in quantum mechanics
  • Investigate the differences between classical and quantum electromagnetic theories
  • Examine the role of quantized fields in modern physics
USEFUL FOR

Physicists, students of quantum mechanics, and anyone interested in the fundamental nature of light and electromagnetic theory will benefit from this discussion.

k9b4
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Is it one wavelength of EM wave? I have googled for this and I can't find an explanation for what a photon is in terms of EM waves.
 
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This is a complicated issue. The photon is the smallest possible excitation of the quantized electromagnetic field. It really does not make much sense to think of it as a classical EM wave, because it is not. Classical EM fields are better described by coherent quantum states.
 
k9b4 said:
Is it one wavelength of EM wave? I have googled for this and I can't find an explanation for what a photon is in terms of EM waves.
It is most definitely not one wavelength of an EM wave.

Quantum electrodynamics (the theory of photons) is a more general theory than classical electrodynamics (the theory of EM waves). Thus, you can explain what classical EM waves are in terms of photons, but not the other way around.

There simply is no classical EM analog of a photon, but there is a quantum analog of a classical EM wave, the coherent state that Orodruin mentioned.
 

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