Differences of the time periods in two independent quantum systems are examined on a semiclassical level. The systems are the electron in the hydrogen atom and a free-electron particle moving in a one-dimensional potential box, respectively. It is demonstrated that in both systems the relativistic correction to the time interval can be expressed as a multiple of the same quantum of time. The size of the quantum is proportional to the ratio of the Planck’s constant and the rest energy of the electron particle.
The Joule-Lenz law for a classical expense of energy is transformed into a formula representing a quantummechanical invariant composed of the interval of energy connected with an electron transition and the corresponding interval of transition time between two quantum levels.Time and energy enter the invariant formula on an equal footing, moreover the time intervals converge with the time periods characteristic for the examined quantum systems.These properties imply to consider the time intervals as quanta of time having character similar to that possessed by the energy.Another result of the transformation of the Joule-Lenz law is the time rate of energy of the quantum transitions.This rate is calculated on a fully non-probabilistic way.When examined for the hydrogen atomic spectrum taken as an example, the obtained quantum rate is by many orders larger than a classical transition rate.