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How to observe interference patterns with a simple experiment?

  1. Apr 19, 2010 #1
    Hello guys, I need desperate help. I am googling an simple experiment that can observe interference patterns ? can someone help me out please?
  2. jcsd
  3. Apr 19, 2010 #2


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    The double-slit experiment is the best known...and is the basic building block of interference experiments.
  4. Apr 19, 2010 #3
    Hello, is it possible to observe that with a diffusion ?
  5. Apr 19, 2010 #4
    I did this for fun in the fall. You need a visible laser, a couple of box cutter type razor blades and a dark room at least 10 feet long. (please please please be careful. I'm talking about razor blades in a dark room. The laser is less dangerous than the razor.)

    Tape the two edges of the blades together so the sharp edges face each other with a very tiny gap, maybe 1/10th of a millimeter.

    You shine the laser through the gap and you will get an interference pattern (vertical light and dark) areas on the wall. The smaller the gap in the blades, the wider the spacing in the pattern. You can also use a single blade edge but the patterns are harder to see.

    Don't look into the beam and don't walk around in the dark holding the razor blades.
  6. Apr 19, 2010 #5
    Here's a very easy method:


    Below is some pictures I have of doing it with a padlock. The shackles on the padlock work nicely if you want to do precise measurements because they come pre-aligned. But you can get it to work even with Coke cans.

    The classic double-slit experiment is also easy. You can also see some impressive ring-shaped interference patterns by reflecting a laser pointer off a slightly dirty mirror.

    The key component in these experiments is the laser pointer. (That and a dark room. Don't expect to be able to see much with the lights on.) Go out and buy one; they're cheap.

    One easy one you can do without a laser pointer is single slit diffraction. Just make a thin gap between two fingers and look at a distant street light through them. The disadvantage there is that you might not understand what's going on unless you know how to calculate a single-slit diffraction pattern, which is a bit more complicated than the double-slit case.

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    Last edited: Apr 19, 2010
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