Feynman, photons and magnetic fields

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SUMMARY

Richard Feynman, in his lectures, discusses the relationship between magnetic fields and photons, asserting that a magnetic field can be conceptualized as composed of many photons. However, this raises questions regarding the nature of static magnetic fields, which do not possess real photons as found in electromagnetic (EM) waves. The discussion highlights that while perturbation theory may introduce mathematical virtual photons, this approach is not ideal for representing static magnetic fields within quantum mechanics (QM). Feynman's tendency to simplify complex concepts for broader audiences is noted.

PREREQUISITES
  • Understanding of quantum mechanics (QM)
  • Familiarity with electromagnetic (EM) theory
  • Knowledge of perturbation theory in quantum physics
  • Basic comprehension of photon behavior and properties
NEXT STEPS
  • Explore the implications of virtual photons in quantum field theory
  • Study the principles of electromagnetic waves and their relation to photons
  • Investigate the limitations of perturbation theory in quantum mechanics
  • Examine Feynman's contributions to quantum electrodynamics (QED)
USEFUL FOR

Students of physics, educators in quantum mechanics, and researchers interested in the intersection of electromagnetic theory and quantum field theory.

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In one of his lectures Richard Feynman describes the effect of a magnetic field on an electron. In doing this he describes the magnetic field as being made up of many photons. If a photon is an oscillating electromagnetic field how can it be just a magnetic field also ?
 
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A static magnetic field does not have real photons as in an EM wave, which needs both E and M (hence "EM"). In some ways of calculating
(perturbation theory), mathematical virtual photons could arise, but that is an awkward way to treat a static magnetic field, even in QM. Feynman, especially in some popular expositions, liked to jazz things up a bit.
 

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