• Support PF! Buy your school textbooks, materials and every day products Here!

Infinite potential well

  • Thread starter victoria13
  • Start date
  • #1
ok so i have a question on infinite potential wells.... if you have the energy state when n=3, does that mean that you have to have the energy state when n=2 and n=1?

Ok basically the Q we are given is:

A particle of mass m is trapped in an infi nitely deep one-dimensional potential well between x = 0 and x = a, and at a time t = 0 is described by the wave function

psi(x,t=0) = sin(pix/a)cos(2pix/a)

(i) What possible values may be found for the energy of the particle?
(ii) What is the expectation (or average) value of the energy of the particle?
(iii) Give an expression showing the time dependence of the wave function, psi(x,t).
[Hint: Use sinAcosB = 1/2(sin(A + B) + sin(A-B))].

so when i use the hint and find the equation in terms of just sin i get

psi(x) = 0.5sin(3pix/a) + 0.5sin(-pix/a)

so does this mean that there is just the 3rd energy state, or the third and first, or all 3?

thanks
 

Answers and Replies

  • #2
vela
Staff Emeritus
Science Advisor
Homework Helper
Education Advisor
14,618
1,253
The particle is in a superposition of the n=3 state and the n=1 state.
 
  • #3
so the energies are when n=3 and n=1?
 
  • #4
vela
Staff Emeritus
Science Advisor
Homework Helper
Education Advisor
14,618
1,253
Yes, the measurement can only result in energies of states which you have some chance of finding the particle in.
 

Related Threads on Infinite potential well

  • Last Post
Replies
18
Views
2K
  • Last Post
Replies
9
Views
1K
Replies
9
Views
2K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
563
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
0
Views
3K
  • Last Post
Replies
2
Views
8K
  • Last Post
Replies
6
Views
5K
  • Last Post
Replies
1
Views
681
Top