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Questions on light and photoelectric effect

  1. Jul 24, 2008 #1
    1. When a certain metal reflects a certain frequency of light, it will kock loose electrons and emit them. Where exactly do these electrons come from? If a metal emits electrons, doesn't that metal eventually gain a positive charge of some sort? Is it possible for piece of metal to lise all of its electrons through the photoelectric effect?

    2. Similar to the question above: when electricity is passing through a power cable, does the copper in that cable lose their electrons or just carry them from another source?

    3. Question on line emission spectrum: does each line in a spectrum represent an electron releasing a photon from a specific energy level? How can one hydrogen atom release an entire series of lines (i.e. Lyman series) if it only has one electron to emit energy for one specific line? The Lyman series of lines has electrons dropping to ground-states from five different energy levels.

  2. jcsd
  3. Jul 24, 2008 #2


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    In both cases, the metal/cathode are grounded.

    A hydrogen gas that you normally use in discharge tubes consists of many hydrogen atoms/molecules, not just one. When you supply energy to them, they all have a distribution of energy that they have absorbed, and thus, can release. You are not looking at just one hydrogen atom.

  4. Jul 24, 2008 #3
    I am not familiar with that term. You mean they have connections into the earth?
  5. Jul 25, 2008 #4


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    Yes. English-speaking people on the eastern side of the Atlantic say "earthed." People on the western side say "grounded."
  6. Jul 25, 2008 #5


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    Not really, I'm from the eastern side and I learned it as "grounded".
  7. Jul 25, 2008 #6

    Andy Resnick

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    The electrons (initially) come from the conduction band of the metal- they are essentially electrons that are free to move anywhere they want to.As the conduction band is depleted, the energy required to remove additional electrons increases, meaning the illumination wavelength must decrease. It's possible to remove tightly bound electrons from atoms with x-rays, so I'd imagine that if you tried, you could indeed strip out all the conduction electrons and many of the valence electrons by the photoelectric effect. At some point, you could not supply enough energy to remove an additional electron.

    Yes- and the series is generated by using different wavelengths of excitation illumination- this moves electrons to different excited states, allowing for the emission lines to appear.
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