## Conceptual Physics (12th Edition)

The amplitude of a matter wave is its wave function $\psi$. The particle associated with the matter wave is more likely to be found where $\psi$ has a large amplitude, i.e., where it is large. The particle is less likely to be found where $\psi$ has a small amplitude, i.e., where it is small.
The probability density function, $|\psi|^{2}$, is the square of the probability amplitude. This is discussed on page 610.