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Home-made QM experiment

  1. Oct 21, 2008 #1
    You will need:
    • 2 flat sheets of cards (debit card sized)
    • 2 small strips of paper
    • Adhesive tape or something else to hold the opaque objects together
    • Laser pointer

    1. Fold each strip of paper at either end of one of the longer edges of one of the cards
    2. Hold both cards together at edges
    3. Join the cards together with tape

    You should end up with a thin slit between the cards. Project a laser beam through that slit and observe results.

  2. jcsd
  3. Oct 21, 2008 #2
  4. Oct 21, 2008 #3
    It demonstrates the wave nature of light.
  5. Oct 22, 2008 #4


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    And that is a "QM experiment"? How? Wave nature of light is a well-known classical observation.

  6. Oct 22, 2008 #5
    wow we're mean. cool experiment if you've never seen it before.
  7. Oct 22, 2008 #6


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    That light is waves is classical. In quantum mechanics particles have also become waves. This is a beautiful demonstration of the uncertainty principle, which definitely holds in quantum mechanics.
  8. Oct 22, 2008 #7
    true statement - but the point ice109 was making is this experiment

    “demonstrates the wave nature of light.”
    Not the quantum mechanics wave nature of particles.

    From around 1810 this is the Young experiment that proved Newton wrong about light being made of particles – it showed it was obviously made of waves. Took a few decades for science to accept that Newton was wrong but they did -

    Until Plank in 1900 showed that light came in quantum units or particles later named Photons. Took a while but Einstein and others drove that point home with Quantum Theory -light came in Photon particles.

    Later as part of building Quantum Mechanics 1920's we see experiments that actually test individual quantum particles going through the same double slit just one at a time (not so easy to do at home) gave the same “wave nature” for photons.
    So the winner at that point is - - Particle / wave duality for the quantum mechanics definition of quantum entities.

    Understanding the nature of the tests helps understand the history of the discoveries.

    Beyond the history of science changing its mind on light four times; I’m all for a fifth change – but cracking the duality point of QM into just one view (particle or wave or ?) is an unknown future.
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