Go to the U of M home page
School of Physics & Astronomy
School of Physics and Astronomy Wiki

User Tools

Trace:
classes:2009:fall:phys4101.001:q_a_1016

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
classes:2009:fall:phys4101.001:q_a_1016 [2009/10/15 22:57] – x500_szutz003classes:2009:fall:phys4101.001:q_a_1016 [2009/10/17 15:05] (current) – x500_choxx169
Line 7: Line 7:
  
 **Main class wiki page: ** [[home]] **Main class wiki page: ** [[home]]
 +
 + 
  
 ==== East End 10/14/09 3:10 pm ==== ==== East End 10/14/09 3:10 pm ====
Line 64: Line 66:
 === prest121 10/15 20:55 === === prest121 10/15 20:55 ===
 The scattering problem is asymmetric because we choose to define it that way.  If we look at the situation of a particle interacting with a potential barrier or well, we obtain equations for the wavefunction in each region.  We *choose* to look at the problem in this way: we are sending particles in from the left side.  Therefore, the particles hit the barrier or cross the well heading to the right.  Some might be reflected back to the left by the barrier/well.  Or they will pass over the well or through the barrier and continue on to the right.  Once the particles are past the barrier/well, there is no reason for them to ever be traveling to the left. The scattering problem is asymmetric because we choose to define it that way.  If we look at the situation of a particle interacting with a potential barrier or well, we obtain equations for the wavefunction in each region.  We *choose* to look at the problem in this way: we are sending particles in from the left side.  Therefore, the particles hit the barrier or cross the well heading to the right.  Some might be reflected back to the left by the barrier/well.  Or they will pass over the well or through the barrier and continue on to the right.  Once the particles are past the barrier/well, there is no reason for them to ever be traveling to the left.
- 
 ====liux0756 10/15 12:15==== ====liux0756 10/15 12:15====
 I am interested in figure 2.19. We can see that at certain energies the transmission coeffiecient is 1, while in the energies between them the transmission coefficient is less than 1. Is this property useful for some practical applications? I am interested in figure 2.19. We can see that at certain energies the transmission coeffiecient is 1, while in the energies between them the transmission coefficient is less than 1. Is this property useful for some practical applications?
Line 81: Line 82:
 ==Spherical Chicken== ==Spherical Chicken==
 But why would there be those levels of energy?  In general, I like our picture, that higher energy creates less significance of the well -- but why would there be those discrete levels that are more or less transparent? But why would there be those levels of energy?  In general, I like our picture, that higher energy creates less significance of the well -- but why would there be those discrete levels that are more or less transparent?
 +===spillane=== 
 +Consider eq. 2.171 the energies are the same old energies associated with energy quantization. Which occurs at discrete allowed energy levels represented by 2.171. So i feel like the corresponding energy levels represented in figure 2.19 come from this eq. En=n²± Vo this will only give discrete energy levels when this difference is precisely one of the allowed energy states of the system. Leading to complete transparency. 
 ====Schrodinger's Dog 10/15 8:24pm==== ====Schrodinger's Dog 10/15 8:24pm====
 Can anyone tell me why differentiability boundary condition doesn't necessarily hold for a infinite square well? Can anyone tell me why differentiability boundary condition doesn't necessarily hold for a infinite square well?
Line 87: Line 89:
 ===Pluto 4ever 10/15 9:41PM=== ===Pluto 4ever 10/15 9:41PM===
 I'm not entirely sure as to why they wouldn't since the only thing we really changed between the two systems is that V is now infinite. Therefore, the chance of a particle escaping the well is non-existent making R=1. Unless, of course, if the walls become transparent. I'm not entirely sure as to why they wouldn't since the only thing we really changed between the two systems is that V is now infinite. Therefore, the chance of a particle escaping the well is non-existent making R=1. Unless, of course, if the walls become transparent.
 +
 +=== Zeno 10/16 9AM ===
 +That's a very good question... the wave function has to be zero outside the infinite square well, and the slope of the sine function is definitely not zero at the well walls; the transmission coefficient could never be greater than zero for an infinite square well, suggested by intuition as well as eqns [2.169] and [2.171]. Griffiths, on pg 71. eqn [2.121], states that <math>\frac{d \psi}{d x}</math> must be continuous //except// at points where potential is infinite, such as the delta function or the wall of the infinite square well.
 +
 +===spillane===
 +This wiki keeps boot'en me off when i go to save what i have edited. is there some limited time frame to editing are is this a common problem, seems to be a new one for me.It happens for creating lecture notes as well, frustrating! 
 +
 +===Yuichi=== You have 15 minutes of inaction.  Then if someone else wants to edit the same wiki, s/he will have a precedence.  but as long as you are typing, you should be able to keep your edit.  If you are losing the edit even if you are not leaving the edit for more than 15 minutes, let me know.  I will check with the systems person. 
 +
 +
 +
 +
  
 ---------------------------------------------- ----------------------------------------------
Line 92: Line 106:
 **Q&A for the previous lecture: [[Q_A_1014]]**\\ **Q&A for the previous lecture: [[Q_A_1014]]**\\
 **Q&A for the next lecture: [[Q_A_1019]]** **Q&A for the next lecture: [[Q_A_1019]]**
- 
classes/2009/fall/phys4101.001/q_a_1016.1255665436.txt.gz · Last modified: 2009/10/15 22:57 by x500_szutz003

Page Tools