Proof for quantisation of electrons energy around an atom?

  1. What is the proof for quantisation of electrons energy around an atom?
  2. jcsd
  3. Simon Bridge

    Simon Bridge 14,487
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    Excellent question - and one which has many answers written about online and in text books etc.
    What have you managed to find out?

    Hint: Balmer series.
  4. Bohr applied the 'plancks black body radiation quantisation' theory to that of atomic world of electrons, and proposed his theory of atom, but does this application of radiation quantisation directly to electrons energy have any proof?
  5. UltrafastPED

    UltrafastPED 1,919
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    Mathematical: solutions to the Shroedinger equation

    Physical: spectroscopic studies

    This is covered in your modern physics course.
  6. Plancks law seems to be a emperical while that of bohr seems to be theory verified later.
  7. Bohr's model of the Hydrogen atom was a first step in the right direction that has been refined and put on very solid foundations since, by Schrödinger, Pauli, Dirac and a few others - as any quantum mechanics 101 lecture will teach you. Planck's law of black body radiation is perfectly consistent with theory, too, even if Planck did not have a full understanding of QM when he formulated it. You can't blame him, it did not exist at the time.
  8. Simon Bridge

    Simon Bridge 14,487
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    ...there is, strictly speaking, no such thing as proof in science (see "the problem of induction" and "empiricsism") ... the observed discrete atomic spectral lines supports the idea that electron energies in an atom are quantized. But it does not prove it.
    I suggested you look up "Balmer Series", did you do that?

    Both these guys were working from prior data, and both sought further data to help refine their theories. This is how science is done.

    There are many experiments which support the idea that electron energies in an atom are quantized.
    I was hoping that you would have made some effort to discover them yourself.

    Scientific models do not rest on just one experiment though - they are supported by the cleverness of the many attempts to disprove them. To go from "this phenomena looks like it works by this rule" to "this phenomena is this way" takes a while and requires quite a bit of evidence.

    Among the many experiments concerning energy quantization in atoms, the following are easily discovered in casual googling.

    Frank-Hertz experiment (historically important - an early clue)
    There's the discrete atomic emission and absorption spectra already mentioned.

    You know a theory is pretty solid when there is a commercial product which relies on it:
    Lasers rely on quantized energy levels for their operation too, so do LEDs - and a range of common semiconductor devices in common use.

    You should read about all these things.

    Conversely - can you think of any experiment that demonstrates atomic electron energies are not quantized?
  9. Thank you for such a clear explanation, Theoretical physics is amazing in the sense application of human intellectual mathematically can do wonders.Its same in the case of bohr,because at that time the electromagnetic theory needed explanation for atomic dynamics by proposing his theory he gave birth to atomic quantum world.
  10. cgk

    cgk 477
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    After seeing a number of seminal experiments and real world devices you conclude that... theoretical physics is amazing?
  11. Many physics inventions are outcome of theories proposed, experimentation is different physical science and theoretical is different.
  12. Simon Bridge

    Simon Bridge 14,487
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    It is a bit surprising that you'd conclude with amazement at theoretical physics from the demonstrations of experimental physics, while, in the next breath almost, talking about how experimental and theoretical physics are "different".

    That kind of thing can raise some concern here about your view of how Physics is done, and the relationship between the experimental and theoretical branches, but it may have been an off-the-cuff remark intended to end discussion ;)

    There are a lot of philosophy of science college courses online - I would urge you look up something like "introduction to empiricism". Unfortunately, philosophy is discouraged here ... so that is the extent of that discussion.

    The standard position is that physics is foremost an empirical science.
    Theoreticians come up with all kinds of wonderful theories and models - general public tends only to hear about the ones that turn out to be successful. You need to remember that for every successful set of postulates there are hundreds of not thousands of failed ideas.

    I seem to find myself repeating the following quite a bit over the last few months:
    Coming up with new theories is the easy part, and it's cheap. The hard part, the expensive part, is choosing between them.
  13. UltrafastPED

    UltrafastPED 1,919
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    Every experimental physicist first does their own theory; otherwise it is rather hard to setup a good experiment! And even harder to explain what they have achieved!

    For the philosophy of physics try "Two New Sciences" by Galileo. He (mostly) did his own experiments, prompted by his own questions in many cases, and then explained them.

    Once you have a sufficient base of experimental results, carefully analysis can produce additional theoretical results .... which must in turn be experimentally verified.
  14. UltrafastPED

    UltrafastPED 1,919
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    You should listen to a couple of physicists "discussing" some effect or problem! New ideas are proposed and shot down rapidly. Then they finally settle on an experimental approach to look into the situation ... something quick is best ... and the experiments settle the discussion.

    Or maybe not! Sometimes the results are ambiguous, with perhaps multiple possibilities. This calls for more discussion, and more experiments.

    Eventually the problem is (a) resolved, or (b) abandoned.

    This cycle occurs with new inventions - things which are created because you need something to solve some other problem.

    It's fun to work on these, especially when your final "product" actually does what is required, and you understand how it works. The stuff that doesn't work is quietly forgotten ...
  15. As an experimentalist, I have the following view:

    The worst possible result of an experiment (other than total failure, which happens often enough) is to be completely and exactly consistent with the prevailing theory. In that case you have learned nothing. The best possible outcome is to shoot down a theory in flames. Because then you have learned something: That this particular theory is wrong, and has to be replaced by something better.

    Unfortunately editors and referees don't always agree.
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