  Conditions under which a quantum particle is described using classical
quantities are studied. The one-dimensional (1D) and three-dimensional (3D)
problems are considered. It is shown that the sum of the contributions from all
quantum corrections (in the WKB sense) strictly vanishes, when a quantum
particle interacts with some specific medium. The indices of refraction of such
media are found. In this case, the smallness of the Planck constant is not
assumed. The momenta of quantum particles in these media and the wave functions
of stationary states are determined. It is found that, for the 1D case, the
wave function is similar to that of the test particle with zero binding energy
in a singular attractive potential, which admits "fall" to the center. For the
3D case with central symmetry, a stationary state, describing a quantum
particle with a classical momentum, is defined by the wave function, which has
the resonance of width about two de Broglie wavelengths.
