where E el is the electric field, B m is the magnetic field, c is the velocity of light, a universal constant in the Universe, ε 0 is the electric permittivity in vacuum and µ 0 is magnetic permeability in vacuum, A is the area of the border of the thermodynamic control volume, and T 0 is the environmental temperature. The entropy production can be related to the analysis of irreversibility of the interaction between a photon and an atomic electron . Here, the fundamental results are summarised in order to be used in the thermodynamic analysis of EPR paradox. To do so, we consider a photon which incomes to the atomic electron. For simplicity, we consider a Hydrogen-like atom, which is an open system from a thermodynamic viewpoint. The incoming photon has an energy E γ = hν and a momentum p γ = hνu c /c, where h = 6.62607004 × 10 -34 J s is the Planck constant, ν is the frequency of the electromagnetic wave, u c is the versor of the speed of light, and c = 299792458 m s -1 is the speed of light . If the photon has a frequency ν = (E f -E i )/h, being E i the energy of the ground state of the electron, E f the energy of the excited level, the electron absorbs the photon and jumps from the ground state into an excited energy state. After the lifetime of this state, on which some considerations have previously been introduced, the electron jumps down into the fundamental state, emitting a new photon. There exists a change in the kinetic energy of the center of mass of the atom, but its amount (10 -13 J) is usually negligible in relation to the energy change (10 -8 J) in electronic transition and its time of occurrence (10 -13 s) is greater than the time of electronic transition (10 -15 s) . However, if we develop a thermodynamic analysis of irreversibility, we must take into account this effect, so that the final energy of the atom, after the photon absorption, results ]: