16.6 Postulate 5. Measurements and the Determination of the State of a System 723
e.Measurement of the energy of a particle in a
one-dimensional box determines the state of the
system.f.Measurement of the energy of a particle in a
three-dimensional box determines the state of the
system.g.The uncertainty in the position of a particle can vanish
only if nothing is known about its momentum.h.The uncertainty in the momentum of a particle
can vanish only if nothing is known about its position.
i.If a system is known to be in a state corresponding
to an energy eigenfunction, the time during which
the system is known to be in that state is infinite.
j.If a free particle moving in one dimension is known to
be in a state corresponding to an eigenfunction of the
momentum operator, nothing can be said about the
position of the particle.