# Infinite potential well

1. Dec 9, 2008

### element1945

1. The problem statement, all variables and given/known data

An infinite potential well with a box in the middle V = 100, the walls of the box go from -L/2 to L/2.

2. Relevant equations

Schrodinger's equation.

3. The attempt at a solution

2. Dec 9, 2008

### element1945

Infinite walls go from -L to L, L = 1 m.

3. Dec 9, 2008

### element1945

i have this equation n= (square root of E)x L/$$\pi$$ and they gave me a) E=23.27432J b)E=26.95434J c)E=105.2461J they ask me to verify wheter the following values of energy are permitted or not to the particle

4. Dec 9, 2008

### element1945

1. The problem statement, all variables and given/known data

An infinite potential well with a finite box inside. The walls of the infinite well go from -L to L.
The walls of the box go from -L/2 to L/2. Verify whether the following values of energy are permitted or not to the particle

a) E = 24 J
b) E = 26 J
c) E= 105 J

m = h bar /2 Kg
V = 100 J
L= 1 m

2. Relevant equations

Schrodinger's equation. double derivative of phi with respect to x + 2m/hbar (E-V) phi = 0

3. The attempt at a solution

I know how to solve for a infinite potential well, but this one has a box inside with V = 100 J and I only know how to solve this with V = 0.

5. Dec 9, 2008

### buffordboy23

How are E and V related?

Last edited: Dec 9, 2008
6. Dec 9, 2008

### element1945

That's schrodingers equation simplified...

7. Dec 9, 2008

### element1945

what are bound states?

8. Dec 9, 2008

### malawi_glenn

Look it up in your QM book

9. Dec 10, 2008

### element1945

thanks ; but where i am right now i dont have one and i am looking on the net ; but no results ; thats why i ask it here but thanks anyway "malawi glenn" and boffordboy 23 thanks you at least try to help me

10. Dec 10, 2008

### malawi_glenn

Why don't you think I am not helping?

(where is my old post?)

I don't know if you dont have a QM book or not, it really helps alot while studying to have text books. And why didn't you just google bound states?

You are obligated to show attempt to solution according to forum rules, I really can't see that you are trying.

Look up in the tutorial session here for intro QM lecture notes, there are at least 2. Then you can google for "particle in a box problems".

How come you want to solve this problem if you don't have textbook? You must then have class notes or similar.

11. Dec 10, 2008

### element1945

thanks and i am new to the forum; i dont have text book or my notebook cause i am on my sister house and i have dialup so is very dificult to see pdf files ; but i will try and read the thinks you say to me ; thanks

12. Dec 10, 2008

### element1945

and i know how to solve a particlein a box but the problem is that this have infinite well and a box inside v=100J so i cant really see what to do

13. Dec 10, 2008

### malawi_glenn

you know how to do it for V = 0 inside the well, why can't you do it for V = 100V?

How do you solve it for V = 0? How would you solve it for an arbitrary V?

14. Dec 11, 2008

### turin

I think element may mean a potential that looks like this:

Code (Text):

|          |
|          |
|          |
|          |
|   ____   |
|__|    |__|

where, by "box", maybe element means the bump in the middle?

EDIT: Thanks, Hurkyl.

Last edited: Dec 11, 2008
15. Dec 11, 2008

### Hurkyl

Staff Emeritus
The normal mode in a post is 'text formatting', not 'artistic design'.

If you want equal-spaced formatting, wrap it in [ code ] .. [ /code ] tags.

16. Dec 14, 2008

### student111

If the box extend all through the well, the problem is just the same as for V=0. If u just have a bumb in the middle of the well, you can use perturbation theory.

17. Dec 14, 2008

### element1945

the problem is just like the drawing of turin thanks

18. Dec 14, 2008

### element1945

but i dont know anything of pertubation theory

19. Dec 15, 2008

### turin

You don't need perturbation theory; however, I think you may get a transcendental equation or something (I don't remember exactly what the solution is like). You know how to do this if you have a uniform potential, V0, right. Well, just do it twice, once for each of the two values of V0. Then, the Schroedinger equation also tells you how to put the pieces together (i.e. it prohibits "jagged" solutions in regions of finite potential).