I'm attempting to duplicate Thomas Young's famous double slit experiment using a laser pointer and some household items, and was wondering if anyone had any suggestions. Rather than using those expensive glass double slit slides, I've attempting to use an edge-on playing card with mixed results. Any thoughts on possible ways of setting up the apparatus?
Young's double slit experiment
- Thread starter OneLastBreath
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michabo
reason, evidence
Playing cards? Not with a laser.
The equation is: lambda / s = x / D, with
lambda = wavelength,
s = slit separation
x = distance between bands
D = distance from slits to detector
If you have a red light laser, lambda is roughly 700nm (700*10^-9m). If you want to see the diffraction, let's say x = 0.01m, D = 10m (if you're indoors). That would mean s= 700*10^-9m * 10m / 0.01m = 0.0007m = 0.7mm. That's pretty tiny. I think you would have a hard time constructing this by hand.
The equation is: lambda / s = x / D, with
lambda = wavelength,
s = slit separation
x = distance between bands
D = distance from slits to detector
If you have a red light laser, lambda is roughly 700nm (700*10^-9m). If you want to see the diffraction, let's say x = 0.01m, D = 10m (if you're indoors). That would mean s= 700*10^-9m * 10m / 0.01m = 0.0007m = 0.7mm. That's pretty tiny. I think you would have a hard time constructing this by hand.
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Hmm...I don't recall where I originally saw the suggestion to use some sort of divider (i.e. the playing card) rather than two slits, but the writer seemed to be convinced it worked just fine. I am familiar with that equation, I was just curious to see if anyone had any suggestions as to how to apply it in order to make a (relatively) simple set-up for performing the experiment.
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michabo
reason, evidence
I'd say take a playing card and an exacto knife and cut a series of vertical bars as close together as you can, stand the card about 10-15m from a wall, and slowly shine the laser over the slits and see what happens. You may be able to make a couple slits that are under 1mm apart. Or you could increase D by doing this in a long, empty corridor which would let you increase x for a given s, or increase s for a given x.
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Get a sheet of glass, paint it black, then scratch parallel lines with a craft knife.
Make a single slit with two old style razor blades.
The gap between slits should be of the order of 0.2mm
T
Make a single slit with two old style razor blades.
The gap between slits should be of the order of 0.2mm
T
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quantumspirit
evangelical humanist
Not just massless particles like photons (light), but also if you do this with massive particles such as electrons, or even whole atoms and molecules, you will get an interference pattern. However, use a detector to detect which slit it goes through, the interference pattern ceases, and you get piles. Turn detector off, and you get interference again.
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I do recall reading that somewhere...maybe the "The Elegant Universe" (Brian Greene). At any rate, a laser seems to be much more accessable than an electron gun. BTW, I finally got the experiment to work the way I originally tried - with an edge on playing card to act as a divider for the beam instead of a double slit plate, and a card with a pinhole in it between the laser and the playing card to make the beam smaller. It wasn't the nicest looking interference pattern, but there were clearly points contructive and destructive interference. I had the chance yesterday to try it with a HeNe laser and a commericially made double slit plate, and the similarity between those results and what I saw with the laser pointer and the playing card is further confirmation that it really did work. Thanks for all the suggestions everybody!
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