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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.
Of course you could try to get some _very_ fine grid, but my physics teacher used just laser and one human hair, and got exactly the desired results (he also had some grids to proof the experiment, tho). This is because IIRC, in a double-slit, only the gap in the between matters (at least when using a laser), so any thin enough object will do.
This is the place where you write something that will make you seem like a complete idiot.
Here's one we did in high school:
Take a piece of smoked glass or painted glass, about 1" high by 2.5" long. Scratch two slits in it with a pin or razor blade. (The instructions at this point in our assignment said "Then take it to the instructor who will tell you that the slits are too far apart. Go back and try again." You will probably need to follow this advice.) Once you get a good double slit, tape over all your failed tries (there will probably be 10 or 15 of them) with black tape.
On another note, igotmyfirstlogon, the description of the original doubleslit experiment is übercool and would probably work better than this.
rollie
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
A couple ideas....
:-)
1) Bolt two single-edge razor blades together, use them the draw parallel slits on smoked glass. It would probably not be wise to give middle-school students access to the blades...
2) Bolt two single-edge razors blade-to-blade. One side can be fixed, the other adjusted by a screw. Instant variable size single slits, and you should be able to make this middle-school student safe.
3) Take out your trusty laser printer and print two vertical lines on a sheet of bright white paper. Photograph it with true B&W film (not that new "color process" junk), cut the film with your handly single-edge razor and install it in a 35mm slide holder.
4) Use the same technique to produce other fun patterns. E.g., besides single and double slits, gratings, etc., there's the starburst pattern where you alternate white and black wedges. Each wedge is 1/2 to 5 degrees wide. You *will* see weird printer artifacts, but you can minimize this by explicitly setting both black and white pixels. (Easy with postscript, I don't know about other tools.)
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken