a nutshell versiol of QM for gre physics

delsub
Posts: 98
Joined: Thu Jun 24, 2010 12:17 am

a nutshell versiol of QM for gre physics

Postby delsub » Fri Aug 20, 2010 6:23 pm

Hi - can someone please help me with this.

I am preparing for p-gre at very short notice.

i have brushed up as much as i could and am now about to start with the 4 question papers solved.

however one major problem remains - quantum mechanics. its to late to open any book now and work through the equations.

Does someone know of any writeup or notes sort of, that can be used to get the hand of P-gre level QM.

One thing is somewhat clear from what i have seen in the question papers - if you know which formula/concept to use you have a good chance to get 50% of the problems right. They dont test you for derivations or theoretical strength.


Anyway, a nutshell version of what i need to know for p-gre QM could greatly solve my problem. Any website, or pdf or anything that you guys could suggest??

Thank you.

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HappyQuark
Posts: 762
Joined: Thu Apr 16, 2009 2:08 am

Re: a nutshell versiol of QM for gre physics

Postby HappyQuark » Fri Aug 20, 2010 10:32 pm

delsub wrote:Hi - can someone please help me with this.

I am preparing for p-gre at very short notice.

i have brushed up as much as i could and am now about to start with the 4 question papers solved.

however one major problem remains - quantum mechanics. its to late to open any book now and work through the equations.

Does someone know of any writeup or notes sort of, that can be used to get the hand of P-gre level QM.

One thing is somewhat clear from what i have seen in the question papers - if you know which formula/concept to use you have a good chance to get 50% of the problems right. They dont test you for derivations or theoretical strength.


Anyway, a nutshell version of what i need to know for p-gre QM could greatly solve my problem. Any website, or pdf or anything that you guys could suggest??

Thank you.


From my experience, the majority of the problems in QM test your understanding of the concepts and foundations of the theory rather than your ability to memorize an equation and crunch numbers. There is typically at least one problem to make sure you know that probabilities are the integral of the wave function squared, at least one checking to see if you know the fundamentals of the infinite square well model (i.e. that it is sinusoidal, that the number of nodes of the sine wave is proportional to the primary quantum number by n+1, that the amplitude of the potential dies off after interacting with the infinite potential walls but that there is some tunneling, etc.), usually one checking your understanding of expectation values, one on the energy levels of a simple quantum harmonic oscillator and frequently one that indirectly tests your knowledge of the Heisenberg Uncertainty Principle. Of course for each of these concepts there is an equation that goes with it, but I would be willing to bet that knowing the equation without the theory will rarely be sufficient to solve the problem but the converse, i.e. knowing the theory but forgetting the equation, will be enough. The only exception to this rule that I can think of was problem 97 from test 9677. Frankly, this question was a bit ridiculous and is probably the type you would want to skip on a timed test like this.

http://physicsgrad.com/pgre/9677-97/

delsub
Posts: 98
Joined: Thu Jun 24, 2010 12:17 am

Re: a nutshell versiol of QM for gre physics

Postby delsub » Sat Aug 21, 2010 12:39 am

Thanks for the reply. fantastic reply.

I dont knwo if it sounded that way but i didnt mean that i was planing to mug a few equations and turn up for the test.

what i meant is that i dont have time to do any sort of indepth study that gives you deep insight sort of thing. so no landau lifshitz.

i meant to say that i want to study QM for the subject GRE - not basics of QM as a fresh student would and gain understanding 3 months down the line. i simply do not have that kind of time.

your elaboration as to the sort of questions - one on the tunneling, one on the potential levels in side an infinite well and one of harmonic oscillator etc - thats just what i wanted to know. So now i have my work cut out.

I do not want to read a "book" - i want to read last minute notes - not merely listing the equations, but also giving some explanations, but only just about enough for the test.

So yes does anyone know of any material on the internet that gives such a nutshell introduction/primer on QM.

Alternatively now that you wrote your reply, if i could just get a list of the 10 odd kinds/types of questions that they ask on QM in the exam, then i could study "top down" for them.

Thanks very much and i look forward to your and anyone else's reply, who may be interested to contribute.

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HappyQuark
Posts: 762
Joined: Thu Apr 16, 2009 2:08 am

Re: a nutshell versiol of QM for gre physics

Postby HappyQuark » Sat Aug 21, 2010 1:22 am

delsub wrote:Thanks for the reply. fantastic reply.

I dont knwo if it sounded that way but i didnt mean that i was planing to mug a few equations and turn up for the test.

what i meant is that i dont have time to do any sort of indepth study that gives you deep insight sort of thing. so no landau lifshitz.

i meant to say that i want to study QM for the subject GRE - not basics of QM as a fresh student would and gain understanding 3 months down the line. i simply do not have that kind of time.

your elaboration as to the sort of questions - one on the tunneling, one on the potential levels in side an infinite well and one of harmonic oscillator etc - thats just what i wanted to know. So now i have my work cut out.

I do not want to read a "book" - i want to read last minute notes - not merely listing the equations, but also giving some explanations, but only just about enough for the test.

So yes does anyone know of any material on the internet that gives such a nutshell introduction/primer on QM.

Alternatively now that you wrote your reply, if i could just get a list of the 10 odd kinds/types of questions that they ask on QM in the exam, then i could study "top down" for them.

Thanks very much and i look forward to your and anyone else's reply, who may be interested to contribute.


Here are a few of the typical types of problems that I was referring to.

Quantum SHO:
http://physicsgrad.com/pgre/9277-56/
http://physicsgrad.com/pgre/9677-98/

Positronium Ground State Energy:
http://physicsgrad.com/pgre/9277-30/
http://physicsgrad.com/pgre/8677-99/
http://physicsgrad.com/pgre/9677-12/

Probability as the integral of squared wave function:
http://physicsgrad.com/pgre/9277-28/
http://physicsgrad.com/pgre/9677-33/
http://physicsgrad.com/pgre/9677-17/

Expectation Values:
http://physicsgrad.com/pgre/8677-56/
http://physicsgrad.com/pgre/9277-51/
http://physicsgrad.com/pgre/9677-77/

Heisenberg Uncertainty Principle:
http://physicsgrad.com/pgre/9277-27/
http://physicsgrad.com/pgre/9677-76/
http://physicsgrad.com/pgre/8677-83/

Infinite Square Well:
http://physicsgrad.com/pgre/9677-18/
http://physicsgrad.com/pgre/9277-53/
http://physicsgrad.com/pgre/9277-29/
http://physicsgrad.com/pgre/9677-51/




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