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Quantum Analogs Newsletter 1 – Quantum Analogs – Acoustic Experiments Modeling Quantum Phenomena The Instrument Quantum Analogs uses sound waves in cylinders and spheres to model the quantum states in semiconductors, hydrogen atoms, and hydrogen molecules. The apparatus includes precisely machined aluminum cylinders, hemispheres and irises. The controller facilitates interfacing the speakers and microphones that generate and detect the sound with the user supplied function generator, oscilloscope and computer used to generate and display the signals. Linear Array: A one-dimensional system is used to create an analog of the particle in a box or a semi-conductor. The wooden base which supports the V-groove used to hold the experimental array, also houses all the extra parts for this system.
Students mount a selection of precisely machined 2” diameter aluminum cylinders, with or without intervening irises, in a specially designed V groove. A speaker is mounted at one end of the V-groove. Once the selected cylinders and irises are arranged, the microphone, mounted in a similar cylinder, is placed at the other end of the array and secured so that the tubes are held together firmly. The system includes three sets of aluminum tubes of lengths 1.25, 5.0, and 7.5 cm and three sets of irises.  In the photograph above, the central iris of a series has been removed in order to explore the effect of a “defect” in a lattice.
Hemispheres: The three-dimensional system uses 4 aluminum hemispheres to create analogs of the hydrogen atom and molecule. The “active” hemispheres used to create the “atom” have both a speaker and microphone mounted in the lower hemisphere and a microphone mounted in the upper. A pair of spacer rings provides three different ways to elongate the “atom”. In this photograph the system is arranged to create a model for a hydrogen “atom”. The BNC connectors indicate the locations of the microphones. The speaker is at the lower right in this photograph. Using the two additional hemispheres supplied, students build a pair connecting spheres which become a model for a hydrogen molecule. At the junction between the upper and lower spheres in the “molecule”, irises of four different diameters can used to explore bonding-antibonding states. Controller: The controller acts as an interface between the source of the signal and the experimental speakers as well as between the microphone and the oscilloscope or computer used to display the amplitude of the sound at the microphone’s location. The function of each part of the controller is displayed in the chart below.
Other Hardware and Software: Some explorations require a user supplied oscilloscope and signal generator. Professor Rene Matzdorf (Universitaet Kassel), with whom TeachSpin collaborated to build this apparatus, has created software which uses the soundcard of a computer both to generate the sound signal and to observe the amplitude of the resulting sound waves. The controller makes it possible to observe the sound wave amplitude simultaneously on both the computer and an oscilloscope. The software, both written and supported by Professor Matzdorf, makes it possible to record up and compare up to four different spectra. Dedicated Website: Professor Matzdorf has created a dedicated website where he has posted a downloadable current copy of the program, a manual for the software and answers to frequently asked software questions. The page also offers several excellent visualization programs that you are welcome to download for your students (http://www.physik.uni-kassel.de/spectrumslc.html). |
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