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Under what conditions is a photon a particle?

  1. May 31, 2015 #1
    I read about the wheeler experiment been done in Australia. But one thing I don't understand. If the particle (but let's use a photon) goes through the two slits (or one) and the screen is removed after it already went through, how is it measured?

    Does it stop after the measurement? My understanding is that when the photon hits the final screen and has no more to go it shows as a wave pattern. But when it interacts when it has still some way to go, it is a particle? So is it sort of hit by other light beams to see what slit it went through along the way to the screen?

    Let's take visible red light for example, under what conditions can it interact and behave like a particle? And why is it so difficult to get light to behave as a particle?

  2. jcsd
  3. May 31, 2015 #2


    Staff: Mentor

    So your question is if the measuring device, the screen, is removed, how is it measured? Easy - it inst. So?

    Its usually destroyed by measurement.

    Forget this wave particle stuff - its a crock. Here is the correct explanation:

    It never is a particle in a usual sense because for photons position is not an observable. As the link above explains the screen at the back measures momentum.

    Last edited: May 31, 2015
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