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Do you own a laser?

  1. Dec 9, 2005 #1
    I was just curios to know how many physicists out there personally own a laser. If you own a laser, what do you do with it?
     
  2. jcsd
  3. Dec 9, 2005 #2
    My own laser

    I am not a physicist but like most Americans I do own a LASER (Light Amplification by Stimulated Emmision of Radiation). Lasers are in all CD players and supermarket scanners. You may own one and not even know it.
     
  4. Dec 9, 2005 #3

    berkeman

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    I have a HeNe that I built from a kit, and a home-made light table. I've used it for many experiments over the years, and even some fun photography stuff. I also build a simple laser scanner at one time for some product ideas I was working on. I have a solid state laser pointer that I've used for simple experiments lately, but mostly my kids play with that one.


    Edit -- I have a pretty good friend (another EE) at work who has some pretty serious lasers at home. Including some medium power CO2 lasers that he uses for etching experiements. He built a computer-controlled X-Y table, and etched logos in wood and metal for friends. Pretty cool. Y'all be careful out there, and wear your safety goggles, okay?
     
    Last edited: Dec 9, 2005
  5. Dec 9, 2005 #4

    robphy

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    I have a laser pointer that I use when I give talks.
    I have a laser printer that I use when I distribute my syllabus.
    I would like to get my hands on a laser and matching ccd camera and do some quantum mechanics demonstrations like http://ophelia.princeton.edu/~page/single_photon.html .
     
  6. Dec 9, 2005 #5

    Danger

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    I'm not a physicist, but I have a really neat pen that my boss gave me. It has not only a laser pointer built in, but also a nifty little blue light for checking the authenticity of money. (Canuk bills have marks that can only be seen properly under blue light.)
     
    Last edited: Dec 10, 2005
  7. Dec 10, 2005 #6
    yeah, I got a laser. My bro and I ripped it out of an old lasar disc player from the 70's. It's an actual HeNe gas tube laser, pretty sweet. It's about as useful as a telsa coil... probably less useful. I wanted to make holograms with it, but thats too expensive.
     
    Last edited: Dec 10, 2005
  8. Dec 10, 2005 #7

    Danger

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    Jonny, don't rule anything out just because it appears to be expensive. In the same manner that you obtained your laser, other equipment might become available. Try to find some surpus outlets or recycling places that might have the requisite mirrors, adjustable stages, etc. for making holograms. For instance, Efton Science (formerly Edmund Scientific) used to have stuff like that at very reasonable prices. I haven't seen one of their catalogues in over 20 years, but they're still in business. I believe that they still have their headquarters in New Jersey.
    Even if that approach doesn't work, keep track of advances in the field of holography. Maybe it will simplify even further. I can remember when the only way to view a hologram was to look through it at the same laser that was used to produce it. Look at where we are now compared to that.
     
  9. Dec 10, 2005 #8

    krab

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    I have a laser pointer I use in my talks. I also use it to exercise my cat. Great fun.
     
  10. Dec 10, 2005 #9
    ya good point. I guess my main problem is I lost my motivation to do it. I've been way more occupied with the theoretical problems in physics more than the hands on practical stuff... maybe after school, and when I've got a steady job, and more time to apply my abilities towards practical things...
     
  11. Dec 10, 2005 #10
    this stuff kind of gets me really aprehensive as to the nature of light... I really wish I understood what is going on in this experiment.

    a few things I consider in the set up:
    the photons of equal energy go through the two slits, and they interfere with each other at the plane of the ccd.

    as a photon hits a pixel in the ccd, it excites an electron in that quantum well (pixel) of the ccd, which is then detected, reset to its ground state, and recorded.

    A photon can't "suck" the energy out of an excited quantum well, it can only add energy.

    as time passes, more photons are detected, and a pattern emerges.


    Putting together those considerations:
    superposition of the photons occurs when two photons are at the same pixel at the same time, otherwise they can't cause constructive or destructive interference. Therefore, in all those dark areas, either photons never reached the detector, or a photon from both slits reached each pixel in those areas at the same time so that they would destructively interfere. Is this how it is interpreted?
     
  12. Dec 10, 2005 #11

    Danger

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    I think, Jonny, that you're combining a couple of things that don't go together. At least, I've never heard of slits being used in a camera set-up, which is what I assume you mean regarding CCD's. That's a straight photoelectric phenomenon.
    The dual slit experiment is intended to demonstrate the nature of light as to its wave-like and particle-like attributes. In that case, it's one photon going through the slit mask, not two. Whether it emerges as a particle or a wave (neither, really, but that's moot) depends upon the experimental set-up.
     
  13. Dec 10, 2005 #12

    Danger

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    Yeah, cats love 'em. I don't know about others, but it confuses the hell out of Lucy if I put the dot on her body. She can see it, but not feel it, so she can't figure out if it's really there or not. She was psychotic when I bought her, and that doesn't help any. :biggrin:
     
  14. Dec 10, 2005 #13

    berkeman

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    :rofl: :rofl: :rofl:
     
  15. Dec 10, 2005 #14

    Tide

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    My cat LOVES them! He chatters uncontrollably then attacks the spot quite agressively and gets annoyed when it goes away. My old cat couldn't care less if there were spots of light roaming the floors, walls and curtains.
     
  16. Dec 10, 2005 #15

    Mk

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    I laughed. :grumpy:

    Here's Edmon/Efton Science: http://www.escience.ca/genSci/
     
  17. Dec 10, 2005 #16

    Mk

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    Cable Descrambler.

    If I say... used one to watch channels I didn't pay for, could the company find out I was using it, if nobody snitched? :biggrin: How much do companies pay the lousy snitches?
     
  18. Dec 11, 2005 #17
    i was talking about this experiment:
    http://ophelia.princeton.edu/~page/single_photon.html

    Ya, I know it's intended to demonstrate the wave-like and particle like nature, and it sure does. But if it works how you say, that it's just one photon going through the slit at a time (the majority of the time), then it will, no matter where it hits the ccd, be detected. Suppose it lands in the dark band region, and a photon from the other slit later in time hits the same pixel. That new photon is 180 out of phase and would've destructively interfered with the first one and the pixel wouldn't have been excited had it arrived at the ccd at the same time as the first photon. The fact that it didn't means that it is going to excite the ccd again, because it can't undo a previously made excitation by the other photon. So if this were to happen in all the dark regions, there would be no dark regions, so the photns must either 1) not arrive at the dark regions at all or 2) arrive at the dark regions at the same time. I disagree with 2 the most, it seems way to serindipitous.
     
    Last edited: Dec 11, 2005
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