In physics, semiclassical refers to a theory in which one part of a system is described quantum mechanically, whereas the other is treated classically.
In this case, there is a clear link between the quantum-mechanical system and the associated semi-classical and classical approximations, as it is similar in appearance to the transition from physical optics to geometric optics.
Max Planck was the first to introduce the idea of quanta of energy in 1900 while studying black-body radiation.
In 1906, he was also the first to write that quantum theory should replicate classical mechanics at some limit, particularly if the Planck constant h were infinitesimal.
[1][2] Some examples of a semiclassical approximation include: This quantum mechanics-related article is a stub.