Phenomena occurring when polarized particles (neutrons, electrons, $\gamma$-ray quanta, and optical frequency photons) pass through polarized targets are examined. The change in the state of polarization of the particles, passing through the target is described phenomenologically in terms of their motion in a pseudomagnetic field. The method of computation is illustrated in detail on the example of a beam of slow monoenergetic neutrons passing through a polarized nuclear target. Results of experiments with neutrons, electrons, and $\gamma$- ray quanta are presented.