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Building Young's Double-Slit Interference Experiment?
TucsonTed asks: "I am a student teacher, preapring for life as a middle or high school teacher. I'd like to build a working model of Young's Double-Slit experiment to show light's wave behavior. Anyone have info on where I can find some blueprints (size of slits, spacing, etc.?) I don't yet have access to a real lab, so I need the DIY approach. I can use monochromatic light or a laser. If you haven't come across this experiment, and its freakish implications at the quantum level, take a look. You may not sleep tonight." For those interested in the math behind this experiment, you might want to check this site.
The really interesting part is that the interference pattern persists even down to the point you are shooting single photons through the slits, as long as you can't tell which slit the photon is going through, but once you can tell, the pattern breaks down and you get just a single blur.
That is, it is an interference pattern as long as the photons are 'allowed' to act as waves, as soon as you try to treat them as particles, they behave as particles.
I'm no physicist, so my description may be a little off, and I don't know how they experimentally verified single photons going through the slit... but this is used for an example of the dual-nature of light.
Another interesting thing is that QM states that when an object passes through an opening nearly the size of the object, the object will be deflected through some range of angles, thus with the proper sized opening, even bowling balls are deflected and would create some sort of interference pattern (sorta :) ), given the correct slits and enough runs.
"Why should I be content to simply live in this world, when I, as a human being, can CREATE it?" - Oertel
The really interesting part is that the interference pattern persists even down to the point you are shooting single photons through the slits, as long as you can't tell which slit the photon is going through, but once you can tell, the pattern breaks down and you get just a single blur.
That is, it is an interference pattern as long as the photons are 'allowed' to act as waves, as soon as you try to treat them as particles, they behave as particles.
You are attempting to explain the "Wave/Particle Duality" nature of quanta. A very good explanation is located here.
From the sound of the experiment, it looks like they use a "quanta source", rather than a photon source (does such a thing exist? Doesn't sound impossible...) - in such case, an electron gun emitting a very low discharge...
I think that is all correct - of course, I am as far from a quantum physicist as can be - correct me if I am wrong...
Reason is the Path to God - Anon
One simple DIY demo is to use a CD and show the interference pattern by reflection. This is the many-slit extrapolation of the double slit problem but it is conceptually similar and it is easy to set up.
The classic explanation of the double slit and its applications to quantum mechanics can be found in Richard Feynman's Lectures on Physics Vol. III or in Six Easy Pieces or Six Not so Easy Pieces which are outtakes from these lectures. The explanation therein is so beautiful that when pertaining to quantum mechanics the double slit problem is often referred to as the "Feynman Double Slit". Putting this into google will return a number of very useful resources.
As a physics lecturer it is hard to avoid Feynman envy.