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Random photon emission

  1. Oct 28, 2012 #1

    I'm studying the wave-particle duality, more specifically the matter-wave function of de Broglie:

    [itex]\Psi[/itex](x,t)=A sin 2[itex]\pi[/itex]([itex]\frac{x}{\lambda}[/itex]-[itex]\nu[/itex] t)

    where [itex]\lambda[/itex] is the de Broglie wave-length and [itex]\nu[/itex] is the frequency.

    The interpretation of this wave is that, [itex]\Psi^{2}[/itex] would be the probability of finding the particle in a certain region of space and time.

    For this to be true, we assume that a point font of radiation emits photons randomly and in all directions.

    I want to know: why is the emission random?.
  2. jcsd
  3. Oct 28, 2012 #2
    Per our current understanding of QM, the universe/reality is that way.

    Randomness is inherent property of the fabric of reality. That's all we can say per our current understanding of knowledge/QM.

    Perhaps there is a philosophical/meta-physical answer to this, namely:

    At the fundamental level things have to be random, else the universe/time-space would not start (be created).
  4. Oct 28, 2012 #3
    I see,

    This is all very new to me, for I am an Electronics Engineering major. This is my first course in Quantum Physics.

    So, basically, we don't really know why it is like this. We can interpret it as being random because Einstein's idea of light intensity is (I=N h [itex]\nu[/itex]), where N is the average number of photons per unit of time that cross a unitary area, in a direction perpendicular to that of the emission.

    Is that correct?

    Thanks :)
  5. Oct 28, 2012 #4

    Welcome to the forum Severo.

    I cannot comment on the above (but it seems right.....;)) as I have not taken any course in QM (and don't know the maths part) nor am I a physicist.

    However there are some physicists in here........:)
    Last edited: Oct 28, 2012
  6. Oct 30, 2012 #5
    You are just messed up with it.You have just used the definition of intensity and the very fundamental formula E=hf,to get it.moreover your sinusoidal wave function for de-broglie has nothing to do with the probability distribution,i.e., it is not for photon but any particle has a probability distribution represented by modulus square of ψ.
  7. Oct 30, 2012 #6
    You should look at it like this: If you have an isotropic source of radiation that emits one photon, what you get is a kind of "photon probability wave" that is also spherically symmetric (exactly like the wave function of an electron).
    The mysterious thing happens when you actually measure the photon (if there is a detector going "blip" or whatever): Then the probability wave collapses. This is the random process that is involved here. What exactly happens during a measurement is unknown - google for "collapse wave function".
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