The basic description of nature is
in terms of probability amplitudes or state functions ψ(**r,**
t) such that |ψ|^{2} is the probability that the system
is found at space-time point **r**, t.

Probability waves have *f = E/h*
and *λ = h/p.*

Knowledge of the position **r**
of a process destroys any information which might have existed
concerning the system's momentum **p**. Similarly knowledge
of the time at which a process occurs destroys information which
might have existed concerning the total energy of the process!

Suppose now we have an
impenetrable-walled cube with a particle inside it. Now we can
have standing waves of probability in three different
directions, resulting in three different quantum numbers, *n _{x},
n_{y} and n_{z}* so that

If two processes can occur in a given experiment, and they are distinguishable, the probabilities add separately, P