We now study the physics of several
simple potentials in one dimension.
First a series of piecewise
constant potentials
for which the Schrödinger equation is
First, we calculate the probability the a particle of energy is reflected by a potential step of height : . We also use this example to understand the probability current .
Second we investigate the
square potential well
square potential well
(
for
and
elsewhere),
for the case where the particle is not bound
.
Assuming a beam of particles incident from the left,
we need to match solutions in the three regions at the boundaries at
.
After some difficult arithmetic, the probabilities to be transmitted or reflected are computed.
It is found that the probability to be transmitted goes to 1 for some particular energies.
Third we study the
square potential barrier
(
for
and
elsewhere),
for the case in which
.
Classically the probability to be transmitted would be zero since the
particle is energetically excluded from being inside the barrier.
The Quantum calculation gives the probability to be transmitted through the barrier to be
We also study the square well for the bound state case in which . Here we need to solve a transcendental equation to determine the bound state energies. The number of bound states increases with the depth and the width of the well but there is always at least one bound state.
Jim Branson 2013-04-22