Real vs. Virtual Photons: A Comparison

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Discussion Overview

The discussion centers on the differences between real photons and virtual photons, exploring their definitions, roles in quantum field theory (QFT), and implications in particle interactions. The scope includes conceptual clarifications and technical explanations related to physics and mathematics.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that real photons satisfy Einstein's energy relation and can be directly measured, while virtual photons do not satisfy this relation and cannot be measured.
  • One participant describes virtual photons as the force carriers of electromagnetic interactions, suggesting that they mediate the repulsion between electrons without energy exchange.
  • Another participant challenges the logic of using virtual photons to explain attraction between particles, questioning how a proton and electron would attract under this framework.
  • Some participants argue that real photons represent physical entities, whereas virtual photons are mathematical constructs used to facilitate calculations in QFT.
  • There is a discussion about the role of fields in interactions, with some participants stating that interactions occur due to fields rather than virtual photons themselves.
  • One participant seeks clarification on the visualization of fields in the standard model and whether it is purely mathematical or has physical significance.

Areas of Agreement / Disagreement

Participants express differing views on the nature and role of virtual photons versus real photons, with no consensus reached on the explanations provided. The discussion remains unresolved regarding the implications of these concepts in particle interactions.

Contextual Notes

Some statements rely on specific interpretations of quantum field theory and the standard model, which may not be universally accepted. The discussion includes assumptions about the nature of particles and fields that are not explicitly defined.

Ezio3.1415
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What is the difference between real photons and virtual photons?
 
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Real photons satisfy Einstein's energy relation (or: they are on-shell). Virtual photons don't. As a consequence, the first can be directly measured, the second cannot.
 
Virtual photons are the force carriers of e.m. While real photons are little packets of energy... When two electrons repulse each other they do it because of the interaction of virtual photons... If they exchaned energy real photon would be emitted and absorbed... And in case of virtual photons no energy is exchanged... Did I get it?
 
you have to be careful about the two repelling each other argument...

how would a proton and electron attract each other with that logic?
 
Welcome to PF!

Hi Ezio3.1415! Welcome to PF! :smile:
Ezio3.1415 said:
What is the difference between real photons and virtual photons?

real photons are physics (they exist)

virtual photons are just maths (they don't)
Ezio3.1415 said:
When two electrons repulse each other they do it because of the interaction of virtual photons...

no, they do so because of the fields

the virtual photons in the maths help us to calculate the fields :wink:
 
As tiny-tim explains, virtual photons appear in between the actual interactions, for the mathematical approach to QFT first used by Feynman. Normal photons enter into interactions (vertices of Feynman diagrams), and they can also emerge. As indicated by the name, you won't see one.
 
Dipstick: I would say the same thing I guess... Interaction! :rolleyes:

Tim: Thank you... Hope to get a lot of help here... The forum's so active... :)

no, they do so because of the fields

the virtual photons in the maths help us to calculate the fields

But I thought standard model visualizes the field with the help of field particles,doesn't it? Or is it just the maths? But it makes total sense... It explains why the range of forces with virtual particles(the force carriers) so well...

Mark:
virtual photons appear in between the actual interactions, for the mathematical approach to QFT first used by Feynman. Normal photons enter into interactions (vertices of Feynman diagrams), and they can also emerge. As indicated by the name, you won't see one.
Can u explain that without Feynman diagram? :confused:
 

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