Quantum Mechanics "Expectation"


by roshan2004
Tags: expectation, mechanics, quantum
roshan2004
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#1
Jun16-10, 01:32 PM
P: 139
1. The problem statement, all variables and given/known data
1. Calculate the expectation value [tex]<p_{x}>[/tex] of the momentum of a particle trapped in a one-dimensional box.
2. Find the expectation value <x> of the position of a particle trapped in a box L wide.


2. Relevant equations
[tex]\psi _{n}=\sqrt{\frac{2}{L}}sin \frac{n\pi x}{L}[/tex]
[tex]<p_{x}>=\int \psi^*p_{x}\psi dx[/tex]
[tex]<x>=\int \psi^*x\psi dx[/tex]


3. The attempt at a solution
I got confused on choosing the limits for both the problems for integrating them. What's the limits I should chose for both the problems.
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Doc Al
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#2
Jun16-10, 02:03 PM
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Where is Ψ non-zero? (What are the boundaries of the box?)
roshan2004
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#3
Jun16-10, 02:14 PM
P: 139
x=0 and x=L

roshan2004
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#4
Jun16-10, 02:17 PM
P: 139

Quantum Mechanics "Expectation"


Thanks I got it. The limits that I have to use are x=0 and x=L
Doc Al
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#5
Jun16-10, 02:22 PM
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Exactly.


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