Can photons propagate in an electrical conductor:


                   There are two main criteria to be met if the emission and absorption of photons in an electrical conductor is to take place . The first criteria is based upon the so-called Debye approximation which states that   , this means that no waves with wavelengths smaller than the spacing between neighbouring atoms can propagate in the crystal lattice of the conductor. The second criteria is the Fermi energy of the conductor which states that no photons can be absorbed unless they equal or exceed the Fermi energy , which for copper is approx. 7 eV. In other words only electrons (or photons ) with greater energy than this  may be available for conduction.   The conduction electron population for a metal is calculated by multiplying the density of conduction electron states r(E) times the Fermi function f(E). For instance for copper which has a  Fermi energy of 7 eV the conduction electron population is calculated as 8.14 x 10 ²⁸ electron/m³;.
               The example of copper wire conduction shows that the mean free path of electrons in a copper wire at room temperature is in the neighborhood of 40 nm. So the energy given to an electron by the electric field by 100 volts applied to a 1 meter copper wire would be on the order of W=eEd = 100 volts x 40 nm = 0.000004 eV. Such an amount of energy cannot be absorbed by most of the electrons because there is no available energy level that close to them in energy. Fortunately in most conductors including copper the valence bands and the fermi levels overlap , but according to the above calculation of an available energy of 0.000004 eV even the availability of electrons would not make much of a difference because of the extremely small energies involved. If on the other hand we were to take photons as the medium of electrical propagation the problems are immediately resolved. The largest permissible wave-length which we have chosen for an individual photon (i.e ) 10 ^-6 m.  is considerably larger than the space between neighbouring atoms which is approx. equal to the atomic radius of 10 ^-8 m. and so would not violate the Debye approximation.  Also if the energy of this photon is calculated it gives about 1.24 eV which is a sufficiently large enough energy to be absorbed by an electron. Photon-induced transitions are not limited to individual atomic electrons. Chemical bonds  are often disrupted by photons which give the bonding electron too much energy to remain in the molecular orbital. The energy which we have suggested of 1.24 eV is sufficient to be absorbed by an electron in the peripheral orbit of the copper atom and to shift it from its orbit.  Thus , taking all these facts into consideration  a good case for photons as the medium through which electrical energy is conveyed in an electrical conductor may be made , including :

• The speed with which electrical energy is conveyed in a conductor .
  
• The amount of energy delivered depending upon the voltage and current .
  
• The electromagnetic fields surrounding an electrical conductor would be explained.
  
• The longer wave-lengths would be understood as belonging to a composite wave made of connected or linked photons.
  
• It would unify the understanding of electrical energy both within and outside the conductor.
  
• It would unify the manner of propagation of photons through a solid.
  
• The theory would  unify all electromagnetic radiation which at present is thought to be different for above light frequencies and those below optical light frequencies.