Originally posted by: Rockinacoustic
I'm taking a class of Quantum Mechanics (No math, just the theory and influence on culture) and I'd love to give an demonstration on a quantum phenomenon. It doesn't have to stick hard to the science, just as long as the idea is well within the material.
Personally I'd love to do something on the double-slit experiment or super positioning. Any thoughts?
Interesting question. I can think of a bunch of possible experiments, though I know some will certainly stand out for their simplicity of execution and impactfulness / visibility of their results.
Certainly low pressure line spectra is trivial to demonstrate with a flame, a bit of salt, and a $2 plastic transmission grating to see the
sodium line doublet at around 589nm , and of course you could do similarly for various elements like copper and so on.
Or of course any low pressure sodium vapor, mercury vapor light bulb would yield immediate results, or a common fluorescent light with its spectral spikes around various lines.
You could set up an EPR type of experiment easily enough, say a proton precession magnetometer to help show the quantized spin states of electrons in water in a magnetic field and their spin resonance with a constant magnetic field. It'd take a bit of EE skill (not much) and probably cost a little more, but I'd expect for $20-$100 especially if you borrow some supplies like a good stereo amp you could do it.
Of course with a $0.15 zener diode or schottky you could demonstrate tunneling or work function / hole / valence band type of effects in semiconductors or as the tunneling current across a barrier. Of course you could do the same with a sharp wire, bit of foil, micrometer, sensitive picoammeter (nanoammeter?) just by looking at closed circuit current through the tip/foil/ammeter vs. the tiny (nanometers) spatial gap between the pointed tip and the foil.
Basically like a little $5 STM... nothing more than a decent $5 op-amp circuit and meter should be required and a borrowed micrometer movement or something.
Of course ferromagnetism itself is a phenomena of aligned spin states so demonstrating the curie point of magnetism and paramagnetic / diamagnetic materials (bismuth is sold in thin sheets for this classroom demo of diamagnetism) you can get into electron spins, boltzmann energy distributions, et. al.
Of course any laser diode or LED or gas laser is an immediate demonstration of stimulated emission and energy levels and excited states etc.
This could be a fun thread, I bet we could list thousands of commonly / easily observable quantum effects and various hypothetical experiments to help demonstrate those.
You could probably do some experiment like millikan's oil drop experiment to show the quantization of charge and determine the charge on the electron in a visible manner.
Any cadmium sulfide photo cell or similar can help demonstrate the quantization of photo-electron ejection vs. material work function since there will be a threshold dependent on wavelength.
Of course the classical Wein law of spectral emission of blackbody radiation by objects at a given temperature is tracable to quantum statistical emission mathematics.
Cooper pairing could be demonstrated with an high temperature superconductor and they sell classroom demo kits for that.
The double slit experiment should be doable with about $20 or less in electronics... it isn't hard to get a PIN or APD photo-diode that is sensitive to single photon events these days, and of course light sources like blue/green LEDs are very controllable and bright sources, and pinholes and slits and stuff are easy to make. It's a bit of a hard demo though since you need uncommon levels of darkness and of course statistical analysis of the photon counts and to hook the photodiode's output to something like the parallel port input of a PC to do the counting etc.
You should be able to demonstrate Zeeman splitting of optical spectra in magnetic fields too I expect with the help of a Neodymium magnet...
Probably Faraday rotation from mirror polished face of a Nd magnet pole too.
You might be able to show some wavefunction and DeBroglie stuff with a vacuum tube and electron beam ala Crookes tube experiments and electron scattering cross sections and such.... Alpha scattering cross sections too perhaps.
It probably isn't even super far fetched to set up an atom trap and see if you can get the optical scattering from a trapped atom photographed (q.v. IBM and various nifty pictures on the web)... though this starts to involve some lab setups that would be more university level than elementary level....
You could probably show the solar prominences in Hydrogen Alpha light at a local astronomy club or arrange to have such an instrument tour your campus since they usually do educational outreach stuff with those kinds of scopes.
A Bubble / cloud chamber wouldn't be hard to build... that could give some cool readings from cosmic rays and so on.
I'm sure I can think of a billion others.. more later.
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