Transmission and Reflection Coefficients of Quantum Particles

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This Demonstration shows the transmission coefficient and the reflection coefficient
of a quantum particle with energy
hitting a rectangular potential barrier. See how the height of the potential barrier
affects
and
by comparing the cases
and
. The dimensionless coordinate
is the product of the wavenumber
for the wave inside the barrier and the barrier width
.
Contributed by: Reinhard Tiebel (March 2011)
Open content licensed under CC BY-NC-SA
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Details
If a quantum particle hits a rectangular potential barrier, then both the transmission coefficient and the reflection coefficient
are periodic functions of the potential width
in the case
, but
and
are decreasing and increasing functions, respectively, in the case
. Furthermore,
and
depend on the quotient
of the wavenumbers
of the incident particle and
of the wave inside the barrier;
. This is shown interactively. The behavior of a quantum particle contrasts with that of a classical particle, where
,
, or vice versa. The "quantum tunneling" effect is a pure quantum effect in the case
. The formulas for
and
follow by solving the time-independent wave equation (Schrödingers equation) with boundary conditions.
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