Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Atomic decay

  1. May 26, 2003 #1
    What is the importance of atomic decay?
     
  2. jcsd
  3. May 26, 2003 #2
    The point of my question was to ask what the importance of atomic decay was in the context of 'the A-word', the anthropic principle. For example, if the strong force was stronger, it would cause nuclear reactions (i believe, correct me if I am wrong) to occur faster than normal, and so stars would die faster, and that would leave less time for life to develop on planets. So, what may I ask is the importance of atomic decay? I know it has something to do with the strong force/weak force but what does it do on its own (that is to say, what does it help with, not what causes it).
     
  4. May 27, 2003 #3

    Integral

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    For starters it is the source of light.
     
  5. May 27, 2003 #4
    I suspect he means nuclear decay

    which usually takes the form of Beta decay. The same constant which governs the rate of Beta decay also affects the rate at which the Sun converts Hydrogen to Helium.
     
  6. May 28, 2003 #5
    Help to whom/what? To a galaxy? To a universe? For Earth?
     
  7. May 28, 2003 #6

    russ_watters

    User Avatar

    Staff: Mentor

    Huh? You're not suggesting that a light bulb is radioactive, are you?
     
  8. May 28, 2003 #7

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    No, he's not. Atoms emit light after deexcitation.
     
  9. May 28, 2003 #8

    russ_watters

    User Avatar

    Staff: Mentor

    So is it a typo? "...it is *A* source of light"?

    Maybe I'm being too nitpicky.
     
  10. May 28, 2003 #9

    Integral

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member


    No it is the ONLY source of light, An atom can be excited in many differnt ways, the result of an atoms electrons being forced to an excited state, is the decay of an electron to a lower orbital. At this point you have light.
     
  11. May 28, 2003 #10
    Atoms emit photons???
     
  12. May 29, 2003 #11

    Integral

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Electron shell interactions is the begining and end of every photon. Photon is simply our word for the exchange of energy between atoms. Sometimes atoms emit energy which interacts with the atoms in our eyes to create the sensation we call "light".

    As far as. did he mean nuclear decay when he said atomic decay??? There is no way for me to know what he meant, I can only answer the question he asked. There is, in my mind, significant difference between nuclear decay and atomic decay. Just as nuclear and atomic physics are two very separate fields. What I am speaking of is interactions involving the atom's electron shell. These interactions are some of the most important to our form of life. Granted it is nuclear reactions that provides the energy to drive our ecosystem, the energy is transfered to earth in the form of atomic interactions occuring in the electron shell structure of the atom. It is these electronic interactions that make life happen.

    The answer to the last question is, Yes, atoms emit photons.
     
  13. May 29, 2003 #12

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I don't think so. As I just noted in another thread, you can get light from Brehmsstrahlung. You can also get it from nuclei and nucleons.
     
  14. May 29, 2003 #13

    Integral

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Tom,
    Is this visible spectrum "light" I thought Brehmsstrahlung radiation was x-ray, it was my impression that the energy range for visible light was electrionic in nature. Do I need to specify light as that electromagnetic radition in the 400nm - 700nm range.
     
  15. May 29, 2003 #14

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    It can be any frequency, depending on the amound by which the electron's kinetic energy was reduced. Also, I forgot to mention that you can get visible light from nuclear fusion. There are certainly no atoms in the sun; all the electrons are dissociated from nuclei.


    That varies from person to person. When I say "light", I mean "EM radiation".
     
  16. May 29, 2003 #15

    Integral

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Is the light* we see directly from the fusion process, or a by product due to electron shell interactions in the photosphere of the sun, where atoms do exist?


    *By the definition I provided above. to most non-Physicists light is what we see, thus when I speak of light I refer to that narrow band we refer to as the visible spectrum, ~400nm-~700nm.

    I generally dislike unqualified statements such as my "Only source of light". Due to Toms objections, let me change that to "Primary source of light"

    I think that if we can agree to call "light" the visible spectrum even Tom will not argue with this statement. :)
     
  17. May 29, 2003 #16

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    It comes about in a number of ways. Under high temperature/pressure conditions such as in the sun, reverse beta decay becomes energetically favored (over beta decay). A product of reverse beta decay is a positron, which is promptly annihilated by an electron in the plasma (I also forgot annihilation!). Each time that happens, you get a photon. These photons can be scattered enough times in their "random walk" outside of the sun to be knocked down to the visible range. Accelerated charged particles in the plasma can give off light, too.

    As for which process contributes what percentage of the total luminosity, I don't know.

    Is it? Like I said, I do not know which processes are most directly responsible for the light we see from the sun. I always thought it was fusion, which would make that the primary source of light (on Earth).

    Nope. :smile:
     
  18. May 29, 2003 #17

    Les Sleeth

    User Avatar
    Gold Member

    Is the on-going process of photon emission due to electrons jumping between orbitals really atomic decay? I thought that was just a temporary situation, whereas "decay" seems to indicate an actual loss of integrity of an atom's structure.
     
  19. May 29, 2003 #18

    Les Sleeth

    User Avatar
    Gold Member

    It interests me that pressure causes reverse entropy (is that a proper interpretation?). I am curious, is the pressure convergent?
     
  20. May 29, 2003 #19

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The word "decay" is an unfortunate relic from the early days of nuclear physics.

    When nuclei "decay" they release light particles and leave behind a lighter nucleus. Early nuclear physicists were able to identify the particles with established mass spectroscopic methods. They understood the process to be a sort of "falling apart" of the nucleus.

    Meanwhile, atomic physicists were studying transitions of electrons in atomic orbitals and

    Today, we know that the above phenomena are of a somewhat similar nature. Nuclear transitions are just jumps from one quantum state to another, just like atomic transitions. One difference is the energy scale involved: atomic transitions are usually 1-104eV, while nulcear transitions are usually 106eV and higher. This means that in nuclear transitions, unlike atomic transitions, mass can be created, giving the appearance of the nucleus falling apart, or decaying.

    A "decay" typically means "transition from a higher energy state to a lower energy state".
     
  21. May 29, 2003 #20

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    No, reverse beta decay has nothing to do with reverse entropy. Entropy is a macroscopic thermodynamics quantity. Talking about the "entropy" of a fusion reaction is like talking about the "temperature" of such a reaction: it makes no sense, because these quantities are averages over a large number of particles. If wuli reads this post, he will jump at the chance to bring up the sorites paradox, because that's what we have here (How many particles do you need for temperature to be meaningful?).

    What does that mean?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Atomic decay
  1. Atom /.? (Replies: 5)

  2. Exponential decay (Replies: 18)

  3. Atom ? (Replies: 4)

  4. Decay constant (Replies: 9)

Loading...