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Do I need E.M. theory for Quantum mechanics?

  1. Feb 11, 2014 #1
    I don't plan to do neither very soon, I still need some pre-requisites.

    But the thing is:
    judging by what I see on books and people talking, E.M. depends heavily on vector calculus and Q.Mech depends heavily on group theory and linear algebra.

    I suck at vector calculus and I'm okay with group theory and linear algebra.
    So based on the MATHEMATICS alone, I'd skip E.M and go for Q.M

    But about the PHYSICS, I just have no idea.
    So I ask:
    how much of E.M one must know in order to study Q.M.?
    Is there vector calculus involved in Q.M. that I dont know of?

    Keep in mind that there is still some time until there. So don't worry, I'll get the hang of vector calculus sooner or later
  2. jcsd
  3. Feb 11, 2014 #2
    If you dont want to work in multiple dimensions (3D/ vectors) then you are going to have trouble with hydrogen. There isnt a shortcut.
  4. Feb 11, 2014 #3
    If you want anything more than a pop-sci version of QM, I'd recommend you focus on learning vector calculus first, as it's essential in almost every physics course you'll take (CM, EM, and QM included).

    You won't even see a large amount of group theory explicitly mentioned in undergraduate treatments of QM (if at all), though linear algebra will still be important.
  5. Feb 12, 2014 #4
    The notion of "sucking" at a particular branch of math is in 99.9% of cases delusional, ridiculous and harmful. You're basically accepting defeat. It's an excuse. If you "suck" at it, just work harder. You should never accept that you're naturally inept at something as important.
  6. Feb 12, 2014 #5
    I found my vector calculus course a lot easier than quantum mechanics! I vaguely remember the schaum book on vectors calculus being very good. I think it's a topic where doing a lot of problems really pays off. Can't remember the title of the book, it was so long ago (!), but I'm sure you can easily dig it out.
  7. Feb 12, 2014 #6
    Well, ok.
    I understand that vector calculus is necessary in a quantum mechanics course.
    And dont worry: I'll become good at it eventually.

    But what I really want to know is how much of Eletromagnetic Theory is used on Quantum Mechanics.

    Basically: Let's forget about the mathematical requirements. What are the physics requirements to study Q.M.?
  8. Feb 12, 2014 #7
    You can learn *some* quantum mechanics without knowing electromagnetic theory, just as you can learn classical mechanics without knowing anything about electromagnetic theory.

    For example, try reading the first six pages of Griffith's standard text on Quantum mechanics in Amazon look inside.

    But all the serious textbooks quickly move on to assuming electromagnetic theory 'cause many of the most interesting/important situations assume an EM field. For instance, the hydrogen atom consists of two *charged* particles. Classical electromagnetic theory predicts the electron will spiral into the nucleus, emitting EM radiation as it goes. To understand why you need to understand a whole out of EM theory - right up to Maxwell's equations. Look at those first six pages of Griffiths again - could you understand them if you knew no classical mechanics? Answer: of course not! Same for any serious examples involving EM fields.

    So read Griffiths "Introduction to Electrodynamics", or a similar textbook, before moving on to QM - note that chapter one is fifty page overview of vector analysis, which might be enough to get you up to speed.
  9. Feb 12, 2014 #8


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    I think you're looking at this the wrong way. EM is one of the most elegant, beautiful, and powerful theories of physics. Forget about QM. You're missing out on a lot of history and insightful physics by trying to sidestep EM. If anything, EM is harder to learn than QM because EM books will not be afraid to go all out and destroy your sanity when it comes to problem sets whereas every QM book I've seen has either ridiculously trivial problem sets or trivial but computationally tedious problem sets. There's a lot of tools in the "physicist's toolkit" that you will learn through a proper study of EM that you probably will have been expected to have honed by the time you attempt QM.
    Last edited: Feb 12, 2014
  10. Feb 12, 2014 #9
    I'm not trying to sidestep it.
    I was just thinking that MAYBE doing EM before QM would be counter-productive and/or counter-intuitive.I was also a little worried that it would be harder than Q.M..
    Well. It probably is harder, but as mentioned in the thread, it is required anyway and thus not as counter-intuitive as I was thinking.

    Anyways, Thanks for clearing that out!
  11. Feb 12, 2014 #10
    E&M before QM is not counter productive since e&m interactions are a part of quantum.
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