Semiclassical physics

In physics, the semiclassical approximation divides a system into two parts, one to be described quantum-mechanically, and the other to be treated classically. In general, it incorporates a series expansion in powers of the Planck constant, resulting in classical physics in the power of 0, and the first nontrivial approximation to the power of (−1). In this case, there is a clear link between the quantum-mechanical system and the associated semiclassical and classical approximations, as it is similar in appearance to the transition from physical optics to geometric optics.