Study on Angular Momentum in Physics

Discusses angular momentum,an important but seemingly difficult concept in physics.An analysis of angular momentum direction in fix axis movement finds the direction different from the fix axis in normal condition while a probe into the angular momentum in atom movement leads to the conclusion that the atomic orbit angular momentum operator are not complete set of mechanical eigenvalues and eigenvectors and the orbit angular momentum operator is non-observable.Points out a quantum physical nature in photon spin angular momentum,which is not corresponding to classical physics.