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Help Quantum Mechanics

  1. Sep 7, 2007 #1
    Help!! Quantum Mechanics

    Help PLZ,

    It's been a couple of weeks since i started Quantum Mechanics I in college. I was getting all A's in every other subject, but I just don't understand ANYTHING when it comes to quantum mechanics. Nothing! Zip... NANA
    So the teacher comes in and dorops some formulas... wells... energy levels... but what the heck are they... And it's not only me, all other students are as confused as I am.
    How did you learn quantum mechanics? was there any book that helped you most?
    Sorry if the topic seems stupid, but i just can't figure this out. I got so mad that I started eating the book...
  2. jcsd
  3. Sep 7, 2007 #2


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    Staff: Mentor

    Calm down. QM is non-intuitive for many (most?) people, me included. But it's reality, especially in the realm of tiny atoms and such, and very important in many fields.

    Feel free to post some specific homework/coursework questions in the Homework Help forums here on the PF. Most likely the Advanced Physics HH forum would be the best place for QM questions. You need to use the HH template that comes up when you start a new Homework Help thread, and you need to show you attempt at a solution before we can offer tutorial help. We don't give out answers here on the PF, but it is usually a very good place to get some tutorial help.

    Welcome to the PF, BTW.
  4. Sep 7, 2007 #3


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    I'll echo berkeman's welcome to the forums. I wouldn't worry that you're not understanding everything a couple of weeks into any course, let alone a quantum course. Also, since you say other students are having troubles too, then it's clearly not you! Just do the usual sort of thing-- take notes during class, read through them afterwards and ask your advisor/lecturer if you have any specific questions. Of course, the PF is a good place to get help too, as berkeman says. You might find it useful to study in groups too: you will probably find that someone will be able to help you with parts you don't understand, and you'll be able to help them with the parts they don't understand. But, most of all, don't worry!
  5. Sep 7, 2007 #4
    Possibly, to put things into perspective it would be useful to read about early history of quantum mechanics: Planck's blackbody radiation, Einstein's light corpuscles, Rutherford-Bohr's model of atom, de Broglie's matter waves, Schroedinger's wave equation, Heisenberg's matrix mechanics, Born's probability interpretation, Einstein-Heisenberg-Bohr philosophical debates. This can make you dizzy, but there is no easy way to understand quantum mechanics. Learning a bunch of formulas will not do the trick.

  6. Sep 7, 2007 #5
    Try Eugene's approach, but if that doesn't work, then maybe learning a bunch of formulas and just working them mechanically might. I learn things better mathematically, so for me it was better to learn the postulates of QM and just to treat it as a mathematical theory at first, until I got comfortable with it. I worried about the physical interpretation after that. I learned it from Cohen-Tanoudji's book, but a lot of people hate that one.

    In any case, just hang in there and find what works for you. By now you know that learning QM is not easy, and you really have to learn to flex your brain in a new way - but many of us found it worth the effort.
  7. Sep 7, 2007 #6
    I would suggest "Feynman's lectures on physics" as a good introductory text. Feynman's clear presentation style has not been matched before or since. Another benefit is that these lectures cover also classical mechanics and electromagnetism, so the transition from the classical to the quantum world is less intimidating.

  8. Sep 7, 2007 #7


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    For a good text book introduction check out, "Introduction to Quantum Mechanics" by David Griffith's
  9. Sep 7, 2007 #8


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    What previous physics courses have you taken, and did they include any quantum physics at all? Where I teach, students who take our "Quantum Mechanics" course are required to already have taken our second-year "Introductory Modern Physics" course which introduces the concept of energy levels in connection with atomic spectra (in particular the hydrogen atom). That course also includes a brief introduction to the quantum-mechanical wave function and Schrödinger's equation. Even our first-year "General Physics" course does a little bit with modern physics and atomic structure.

    If you and the other students in the class really haven't seen any of this stuff before, then you should discuss this with your instructor. He/she may have unrealistic expectations of your background. I can imagine that this might be possible at a large university where there are a lot of courses and a lot of professors, who can't all keep track of what everyone else is teaching. Or your instructor might simply be new at this.
  10. Sep 7, 2007 #9


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    As the others say, I agree. QM is not so easy to learn, due to its nonintuative nature. Only mathematics can describe it properly. So good knowledge in caclulus and linear algebra is a must, even at introductory level. Also background knowledge in modern physics at low level is good so have some sort of physically feeling for what is going on. And also Feynmans lectures on QM is very good (i think it is in vol3 if I remember right), and Griffiths book is awesome.

    What material do you use in this course? And what is your background in maths and physics?

    A well is some potential that is attractive, for example the coloumb field from the atomic nuclues is a potential well for electrons. And energy levels is due to the wave-nature of particles, not all positions are allowed in the well, and some are more probable -> leads to energy levels, not all energies are allowed either.

    This is a quite good place to have info from too:
  11. Sep 8, 2007 #10
    Recommended Wikibook

    Take a look at this Wikibook. It's far from complete, but it helps reduce the initial slope of the learning curve.
  12. Sep 8, 2007 #11
    Thanks guys,
    I'll start reading a introductory modern physics book this weekend. I was able to find feynman lectures too. I guess my problem is that I don't have a good background.
  13. Sep 8, 2007 #12
    Don’t worry, you are not alone.

    Regards, Dany.
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