This review of Quantum Physics Online (English Version) covers only the section on wave mechanics. I am a junior undergraduate physics major who has completed a course in modern physics, and I have also been exposed to material generally covered in the first few chapters of an undergraduate quantum mechanics text. My response to this site is extremely positive. The animations concerning both the wave-packet propagation and the steps and barriers clearly illustrate concepts that I had not yet been able to clearly visualize. When I take a quantum mechanics course in the fall and will be more actively studying the mathematics of the subject, I intend on returning to this site for a better-informed pass at the wave mechanics applets, as well as the additional material of the site. Comments concerning the specific material reviewed follow:
Wave-particle duality in a Young slit experiment: I found the animation an excellent representation of the particle-wave slit experiment and was reminded of Feynman scratching out probability curves on his blackboard. I cranked up the rate of the ?lumps? being fired and watched as the curves on the histogram smoothed out to the nearly continuous distributions expected. Simple and very nice.
Propagation of a wave packet: Having scratched my head more than once trying to visualize a ?wave-packet propagating through space?, this applet and some re-reading of textbook material helped me to make some headway on this subject, at least two-dimensionally. I liked that one could specify to watch either the absolute square of the wave function or the real part of the wave function. That the parts of the wave-packet with the greater momentum will propagate faster causing spreading of the wave-packet makes sense when you can watch it happen. I like the option of varying the width (from .5,
1,2) of the wave-packet, assuming that the numbers .5,1,2 correspond to relative widths. This variable ?width? isnice to show that the more localized the packet is initially, the quicker it spreads out in space due to the correlation of increased localization and increased uncertainty in momentum. That the parts of the packet with larger momentums would propagate with larger velocities is nicely seen, though I would prefer to see the animation progress a bit longer than it does. Quibbles.
Propagation of non-minimal wave-packets: Just a variation on the previous, excellent wave-packet applet. The wave-packet localizes and then spreads due, as I have read, to the different initial configuration of momenta in the packet. I have also read that outside measurements will collapse a wave-packet, only for the wave-packet to then spread out or ?grow? with time, collapsing again at each additional measurement. How exactly is this phenomenon related to the non-minimal wave-packet portrayed in this applet?
Steps and Barriers: This is the section for which I have the least exposure and understanding. Again, the animation of quantum tunneling appears to be a wonderful treatment of the subject, but since I am not versed in the mathematics of the phenomenon, in my eyes it still smacks of witchcraft, something I hope that will pass with further exposure. Varying the step size to watch the relative amount of the wave reflected and transmitted is a very instructive exercise, and I look to revisit this applet in the near future when I am better armed.
Scanning tunneling microscope: Our excellent electronics instructor here at Humboldt State has spoke on this topic a few times,
and this applet reflects exactly what I have already learned on the subject (on a relatively qualitative level). The applet provides a nice, fairly qualitative look at the subject, and the interactive part is instructive--calling it a game might be a bit of a stretch.
I applaud the design and operation of the applets. While they were fairly sizable, the load time on my 56K modem was only about ten seconds?well worth the brief wait. There were a few typos noticed, and the brief encroachment of French on the English site (e.g. barriere). The author has obviously paid great attention to detail throughout, both in the programming and in the physics. I offer only my compliments.