IS ANGULAR MOMENTUM CONSERVED IN A QUANTUM MECHANICAL SYSTEM?

According to the principle of uncertainty, all three components of the angular momentum cannot be simultaneously determined. It is not that we do not have best devices that cannot measure the angular momentum components simultaneously. It is just that for a quantum mechanical system, if we know Applications of the Formalism-II 159 the angular momentum of one of the components, then we are completely uncertain about the other two. In simple words, the other two components do not even exist, and without the other two components, we cannot know the angular momentum of the system. Thus, for a quantum mechanical system, since we are uncertain about the angular momentum, we cannot be certain about the conservation of angularmomentum as we are in classical mechanics. In the following example, the closest meaning of conservation of angular momentum in quantum mechanics is discussed.