The concept of virtual photons is part of the theoretical framework of quantum electrodynamics (QED), which describes the electromagnetic interaction between charged particles. In QED, particles such as electrons interact through the exchange of virtual particles, specifically virtual photons in the case of electromagnetic interactions.
When two electrons are near each other, they interact through the exchange of virtual photons. These virtual photons are virtual particles that mediate the electromagnetic force between the electrons. They are called "virtual" because they do not correspond to observable or detectable particles in the same way as real photons.
The interaction between the electrons occurs through a process called electromagnetic scattering. One electron emits a virtual photon, which carries energy and momentum, and the other electron absorbs this virtual photon. The exchange of the virtual photon alters the momentum and energy of the electrons, resulting in an electromagnetic interaction between them.
Now, when the electrons are very far apart, the interaction between them can be approximated using classical electromagnetism, specifically Coulomb's law. Coulomb's law describes the electrostatic interaction between charged particles and is valid in the classical limit.
In the classical limit, the electromagnetic interaction can be understood as the exchange of real photons, which are observable particles of light. However, at larger distances, the contribution of virtual photons becomes less significant, and the behavior of the electrons is well described by Coulomb's law, which predicts the repulsive force between like charges.
In summary, the appearance of virtual photons when two electrons are near each other is a quantum mechanical phenomenon described by QED. At larger distances, where the quantum effects become less significant, the behavior of charged particles can be approximated by classical electromagnetism, and Coulomb's law accurately predicts their repulsion.