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Applets for quantum mechanics

Rating: 4 stars
Used in Course: Not used in course
Submitted by: Franziska vonHerrath (Student), May 01, 2001
Comment: This site does a beautiful job of visualizing otherwise difficult to conceive
aspects of quantum mechanics. With their changeable conditions, the applets
inspire great curiosity for the layman to inquire more in depth about the
presented topics as well as clarification for the a little more advanced physics
student. In either case, the applets invite the user to spend ample time with
the concepts.The applets are not only very helpful and sound, but also an
aesthetically pleasing supplement to any Quantum Mechanics/Modern Physics book.
Minor technical flaws overal do not distract from the site's easy to use,
instructing applets.

Wave/Particle Duality in Quantum Mechanics
This site superbly visualizes the Young slit experiment. The posed question
about the reason for the decrease in noise the when more particles have hit the
screen guides the reader in the right direction to think of the experiment in a
statistical manner.

Propagation of a Free Wavepacket
The otherwise difficult to envision propagation and successive spreading of a
wavepacket is playfully illustrated here. The only improvement suggestions I
have are
1) To enlarge the graph in which the waves are spreading. This way the waves of
width 1 and 2 would more clearly show signs of spreading by the time they reach
the graph's end in both the probability density as well as in the real part of
the wave function.
2) To include the wavepacket's propagation in momentum space as it is so tightly
related to configuration space.

Propagation of a Non-Minimal Wavepacket
This illustration is an excellent follow up to the previous applet. Not all
wavepackets start propagation from their minimum size. The non-minimal
wavepacket first contracts in configuration space as the waves with higher
frequencies at the trailing edge "catch up" to the bulk of the wave and then
spread ahead of the rest.

Steps and barriers
This applet smoothly visualized a gaussian wavepacket hitting a step potential
under various conditions. The reflection, interference and transmission are
evident and well executed. The user really benefits from the changeability of
the energy of the step potential. There is one thing that demands change for the
text to be physically sound: The second paragraph should read "When the step
height is less or smaller ?" It would also be nice to see what happens when a
wavepacket hits a finite barrier of step height less than its particle energy.

Scanning Tunneling Microscope
This applet is a fun and thoughtful addition to the previous visualizations as
it provides a bridge from theoretical to measurable physics. I suggest
explaining what is meant by the "sample." The electric green color made me think
of GAK, which the sample is not.

Technical Remarks:

Spelling and grammar need some attention to make the texts a non- distracting,
flawless reading. A better compromise between tex box size and applet size
could also be found. When manipulating an applet would be moe helpful to be able
to read the whole featured explanation text rather than merely one sentence at
a time.