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classes:2009:fall:phys4101.001:q_a_1123 [2009/11/23 17:36] – x500_porte210classes:2009:fall:phys4101.001:q_a_1123 [2009/11/28 22:18] (current) – ely
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-===== Nov 23 (Mon)  =====+===== Nov 23 (Mon) Spin operators, probabilities, Larmor precession, S-G experiment =====
 **Return to Q&A main page: [[Q_A]]**\\ **Return to Q&A main page: [[Q_A]]**\\
 **Q&A for the previous lecture: [[Q_A_1120]]**\\ **Q&A for the previous lecture: [[Q_A_1120]]**\\
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 **Main class wiki page: ** [[home]] **Main class wiki page: ** [[home]]
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 ====Daniel Faraday 11/22 6pm==== ====Daniel Faraday 11/22 6pm====
 In the proof that [L^2,Lx] = 0 on page 161, how does Griffiths get from the first line to the second line? In the proof that [L^2,Lx] = 0 on page 161, how does Griffiths get from the first line to the second line?
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 Cathode ray tubes (http://en.wikipedia.org/wiki/Cathode_ray) are pretty standard for creating electron beams. There is plenty of information out there on them if you are curious. Cathode ray tubes (http://en.wikipedia.org/wiki/Cathode_ray) are pretty standard for creating electron beams. There is plenty of information out there on them if you are curious.
  
 +== Zeno 11/25 9am ==
 +I knew there was something obvious that I was overlooking. Thanks!
 +
 +===David Hilbert's Hat 11/25 12:30pm===
 +As far as I know they actually cooked silver atoms from a furnace. Wikipedia mentions that you need to have particles with a total electric charge of zero because otherwise they would deflect under the influence of a magnetic field before coming out of the apparatus - http://en.wikipedia.org/wiki/Stern-Gerlach seems to suggest that anything with a total neutral charge and unpaired electrons orbiting it can be used. If I recall correctly there is a pretty lengthy description of it in the 2000 level quantum book. 
 +
 +===David Hilbert's Hat 11/25 1pm===
 +Also http://hyperphysics.phy-astr.gsu.edu/Hbase/spin.html seems to have a few extra details about the silver atoms. 
  
-====John Galt  11/23  5:35 PM==== +===Dark Helmet 11/28 10:15=== 
-Does anyone see anything useful coming from taking the time derivative of A(t) and B(t) as described in class and setting it equal to zero? In a magnetic field, will there ever be a time period over which the probability of finding a particle spin up or spin down will not change at all?+I don't know if it is exactly the same thing, but a free-electron laser would be a beam of electrons.  Or is that a laser made from accelerating electrons?  Now i can't remember.  Well, anyway, an electron beam wouldn't be perfectly precise even in a perfect vaccuum due to the uncertainty in the beam width.  Another one of those uncertaintly principle relations
  
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classes/2009/fall/phys4101.001/q_a_1123.1259019408.txt.gz · Last modified: 2009/11/23 17:36 by x500_porte210

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