Principles and Concepts
of Quantum Mechanics
of Quantum Mechanics
Implications of
Quantum Mechanics
Quantum Mechanics
13a. Details of Small Parts.
Summary
In contrast to the classical case, a small part of the wave function of quantum mechanics carries the full mass, energy, momentum, spin and charge. Details.
We will illustrate here the idea that a small part of a wave function carries the full energy and momentum, but the argument would be similar for the other properties (spin, charge, mass) and for any kind of ‘particle.’
We shoot a spin






Now the wave function goes through the magnet and splits into two parts,







To put the argument another way, mass, energy, momentum, spin, and charge are independent of the norm (size) of the wave function. So each small part (having a small norm) carries the same amount of these quantities as it would if the norm were 1.