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[Q]Queation about Photon and Electric discharge.

  1. Mar 29, 2009 #1
    Hi, I just wander what hapeens if photon which energy is higher than difference of adjacent

    energy levels collide with atom? How does Excess energy go? transmiting atom by form of

    photon or giving motional energy to the atom?


    Second Question is What does process ocurrs when enough voltage to make dielectric

    breakdown imposes to gas?

    I know electric force imposing positive and negative charge 'tear' atom and separate

    opposite charge, but in aspect of energy, just another external potential is added to the

    atom and i can't image tearing atom in this view.

    How can you explain tearing atom with aspect of energy, not force?
     
  2. jcsd
  3. Mar 30, 2009 #2

    alxm

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    Science Advisor

    Depends on what kind of transition you're talking about. E.g. if you're talking about ionizing radiation, which ejects an electron entirely, then surplus energy can go into the kinetic energy of the electron, which is continuous once the thing is free.

    But in most cases, the photon simply won't be absorbed. Just look at some transparent material like glass, which will absorb most IR, but is transparent to visual light which is higher in energy.

    Well, force and energy are always related. But what happens is that, between your two electrodes, you always have a probability the electrons will fly across space from one to the other. The higher the voltage, the higher the probability that will happen. For low voltages the probability, and thus current, is practically zero. But once they do start flying across, they hit and ionize the gas (ejecting electrons) which in turn makes it easier for other electrons to pass. In other words, the relatively unusual situation that resistance decreases with current. (Which is why fluorescent lights need an electrical ballast)
     
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