Potential Barrier in Infinite Well: Equal Amplitudes Both Sides?

In summary, the potential well set up exactly like this https://www.physicsforums.com/showthread.php?t=397977&highlight=potential+barrier+inside+an+infinite+square+well has a barrier in the center that causes an amplitude to be smaller on the side of the barrier.
  • #1
Oliman
3
0

Homework Statement



The well is set up exactly like this https://www.physicsforums.com/showt...ential+barrier+inside+an+infinite+square+well. It is basically a infinite potential well with a barrier in the center.

Basically I've got solutions for regions 1, 2 and 3, found some allowed energy levels. In region one we have Asin(k1x) and in region 3 I have Dsin(k1x), when I use the continuity conditions to solve for the constants I find that A=-D. This means that when I plot the wave functions I end up with equal amplitudes on either side of the barrier. I would have thought that the amplitude in region three is smaller than the amplitude in region one. Can anyone tell me which is correct?

My apologies for not having it in the normal form but I thought because I'm not asking for help with a question but merly asking whether my result is feasible this form makes more sense. Also my apologies for my lack of latex but for some reason it wasn't working :-(. Sorry this is my first post (if you hadn't already guessed! ;-)
 
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  • #2


Why is region 3 described by only [itex]D\sin(k_1 x)[/itex]?

You would want [itex]\Psi(2a+2b) = 0[/itex], which doesn't necessarily throw out the cosine term.

In fact it might be easier to just change the coordinate system so that the origin is in the center of the well. Then due to the symmetry of the potential, you just look for symmetric and antisymmetric wavefunctions.
 
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  • #3


Hi Nickjer, Thanks for the reply. In actual fact I did translate the cordinate system so the center of the well was at the origin and then looked at odd and even functions within the well but left region three as sin. Shall I solve for my constants in the usual way except using a linear comination of sin and cos in region three? Should I take into account the symmetric and antisymetric properties just in region two or region three as well?
 
  • #4


Oliman said:
This means that when I plot the wave functions I end up with equal amplitudes on either side of the barrier. I would have thought that the amplitude in region three is smaller than the amplitude in region one.
Why would you expect that? Is there something different about region 3 that would cause the amplitude to be smaller there than in region 1?
 
  • #5


vela said:
Why would you expect that? Is there something different about region 3 that would cause the amplitude to be smaller there than in region 1?

I thought that when something transmits through a barrier the amplitude gets smaller. I guess I thought that was a kind of rule. Am I wrong in thinking this?
 
  • #6


There is no transmitting here. A particle isn't incident from the left and transmitting through the right. You have a standing wave with a barrier in the center.

And yes, you should start off with a linear combination of sin and cos on both sides of the well. If it is a symmetric function then you will want a mirror image of the function on both sides (replacing x->(-x)). If it is antisymmetric, then you will want symmetry about the origin.

In both cases the amplitude on either side will be related. Just don't forget to solve for the BC's at the boundary.
 

1. What is a potential barrier in an infinite well?

A potential barrier in an infinite well refers to a barrier or energy barrier that exists within an infinite square well potential. It is usually represented by a step-like function that separates one region of the well with a higher energy level from another region with a lower energy level.

2. How is the potential barrier created in an infinite well?

The potential barrier in an infinite well is created by the presence of a potential energy function, which can be represented by a step-like function or a potential step. This potential energy function serves as a barrier that separates different energy levels within the well.

3. What is the significance of having equal amplitudes on both sides of the potential barrier in an infinite well?

Having equal amplitudes on both sides of the potential barrier in an infinite well means that the energy levels on both sides are equal, and there is no difference in the energy levels between the two regions. This leads to the formation of a symmetric potential well, which has important implications in quantum mechanics.

4. How does the presence of a potential barrier affect the behavior of particles in an infinite well?

The presence of a potential barrier in an infinite well can affect the behavior of particles in several ways. It can lead to the confinement of particles within the well, resulting in quantized energy levels. It can also lead to the formation of standing waves, which influence the probability of finding a particle in a particular region of the well.

5. What are the applications of studying the potential barrier in an infinite well?

The potential barrier in an infinite well has various applications in physics, particularly in the field of quantum mechanics. It can help us understand the behavior of particles in confined systems, such as atoms and molecules. It also has applications in the study of semiconductors, where the potential barrier plays a crucial role in the flow of electrons.

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