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classes:2009:fall:phys4101.001:q_a_1211

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classes:2009:fall:phys4101.001:q_a_1211 [2009/12/10 22:07] – x500_liux0756classes:2009:fall:phys4101.001:q_a_1211 [2009/12/15 11:49] (current) – x500_sohnx020
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 ===liux0756 12/10 22:00=== ===liux0756 12/10 22:00===
 I guess the A in the quiz is equal to 1/A in the textbook. I guess the A in the quiz is equal to 1/A in the textbook.
- 
 ====poit0009 12/10 12:35==== ====poit0009 12/10 12:35====
  
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 <math>\\ \\ \\P_{+\frac{\hbar}{2}}=\frac{1+2\cos{\theta}+\cos^2{\theta}}{4\cos^2{\frac{\theta}{2}}}\\ <math>\\ \\ \\P_{+\frac{\hbar}{2}}=\frac{1+2\cos{\theta}+\cos^2{\theta}}{4\cos^2{\frac{\theta}{2}}}\\
 P_{-\frac{\hbar}{2}}=\frac{\sin^2{\theta}}{4\cos^2{\frac{\theta}{2}}}</math> P_{-\frac{\hbar}{2}}=\frac{\sin^2{\theta}}{4\cos^2{\frac{\theta}{2}}}</math>
 +
 +===Daniel Faraday 12/11 830 am===
 +Yes, the probability should have theta in it. I think you can consider theta to be a value given in the problem, or something that could be experimentally determined.
  
 ====Andromeda 12/10 2PM ==== ====Andromeda 12/10 2PM ====
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 If the z-component keeps increasing, then it could definitely exceed the total angular momentum.  Take the l=1 case.  Here we can have <math>m_l</math> = -1,0,or 1.  If you apply <math>L_+</math> to the -1 state, you return the zero state.  If you apply it to the 0 state, you return the +1 state.  If you apply it to the +1 state, you would end up with <math>L_z</math> being +2.  This doesn't make any sense.  The angular momentum in the z-direction would be greater than the particle's total angular momentum. If the z-component keeps increasing, then it could definitely exceed the total angular momentum.  Take the l=1 case.  Here we can have <math>m_l</math> = -1,0,or 1.  If you apply <math>L_+</math> to the -1 state, you return the zero state.  If you apply it to the 0 state, you return the +1 state.  If you apply it to the +1 state, you would end up with <math>L_z</math> being +2.  This doesn't make any sense.  The angular momentum in the z-direction would be greater than the particle's total angular momentum.
  
 +
 +===liux0756 12/10 22:10===
 +The z-component cannot exceed the total because <math>|L|^2=|L_x|^2+|L_y|^2+|L_z|^2 \ge 0+0+|L_z|^2 =|L_z|^2</math>.
 ====Super Hot Guy==== ====Super Hot Guy====
 Question 3a: Question 3a:
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 ===liux0756=== ===liux0756===
 I get <math>J_+|\Psi>=\hbar\sqrt{2}|1,0>|\frac{1}{2},-\frac{1}{2}>+\hbar|1,-1>|\frac{1}{2},\frac{1}{2}></math> I get <math>J_+|\Psi>=\hbar\sqrt{2}|1,0>|\frac{1}{2},-\frac{1}{2}>+\hbar|1,-1>|\frac{1}{2},\frac{1}{2}></math>
 +===Andromeda 12/10 10:37pm===
 +I have <math>J_+|\Psi>=\hbar\sqrt{2}|1,0>|\frac{1}{2},-\frac{1}{2}>+\hbar|1,-1>|\frac{1}{2},\frac{1}{2}></math> too.
 +===Devlin  12/10===
 +That is what I get also.
 +===Captain America 12/11===
 +I got the same as Liux, Andromeda, and Devlin.
 +===Hydra 12/11===
 +That's what I was getting, but is there more work to show for this?  It seems, .....too basic???
 +===Dark Helmet 12/11==
 +Where does the root2 come from?  It seems like this whole problem can be done just by reasoning except for the root2.
 +===Andromeda 12/11 1:40pm===
 +equation 4.121: <math>A_lm=\hbar\sqrt{(l+-m)(l-+m+1)}</math>
 +
 +====Anaximenes - 23:45 - 12/10/09====
 +This is a normal length test, right (i.e., 50 min.)?  I'm wondering why the practice test has 5 questions.  Are other people expecting 5 questions?  Do you think the idea is that we'll have 5 really short questions, or that there will be a very lenient curve?
 +
 +===Captain America 1:05 12/11/09===
 +I don't think it will be 5 questions long, I think he just wants us to know how to do these things.  I expect it to be as long as the previous tests (well, hopefully not the first one since that one did take too long).  I don't think he wants to create curves, he would rather we just do well.  Good luck everyone!
 +
 +=== joh04684 0125 12/11/09 ===
 +Just like for the last test, this isn't actually a practice or previous test...It's a list of the types of problems we should know how to do for the test, and I don't think should be comparable in length.
 +
 +=== Zeno 12/11/09 ===
 +I would agree with the previous two comments; it's just a sample of what we should know how to do for the exam. This last section since the last exam has covered quite a bit of material, and there's a lot that we can do with it, so the example problems are meant to be a supplement to studying: if you can sit down and do the example problems without outside reference material then you'll do well on the exam. If you get stuck on a certain type of problem then you know that's what you need to work on before the exam time. Also, each exam in the past has always had a problem that's very similar to one on the practice exams...
 +===Devlin===
 +Also, I don't see a question in number 4, just a bunch of statements.
 +
 +=== Zeno 12/11 ===
 +Yeah, this puzzled me as well. I think we're being subtly asked to find the normalization factor like in problem 4.18 from HW 10.
 +
 +===Dark Helmet 12/11===
 +I didn't see one either, maybe it was just useful information??
 +
 +===The Doctor 12/11===
 +I just assumed it meant to show how to find it using the given relations.
 +
 +====Hydra 12/11 post-test!====
 +Hey, how do you do the first exam problem from today?
 +
 +===Blackbox ===
 +Well, it was difficult for me and I have no idea what I have to say about the test.
  
 +====Dagny====
 +For first order theory, infinite square well, how do we know when to integrate over entire well or just parts of well?
  
 +====Links====
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classes/2009/fall/phys4101.001/q_a_1211.1260504438.txt.gz · Last modified: 2009/12/10 22:07 by x500_liux0756

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