  In the experiments considered here, we measure the y-component of momentum
for a particle passing through a system of slits. The source-slit system is the
preparation apparatus that determines the state vector. Recognizing that a
system of slits is a position-measuring device allows us to ascertain that the
state vector is a position state. Then, writing the state vector in momentum
space provides a straightforward calculation for the probability amplitude and
its corresponding probability function. Interference effects, if any, are
inherent in the probability function We determine the statistical distribution
of scattered particles for four different slit systems. The results are in
agreement with the well-known interference patterns obtained in classical wave
optics.
