# Homework Help: Expectation values for a harmonic oscillator

1. Mar 31, 2010

### KaiserBrandon

1. The problem statement, all variables and given/known data
I need to find <x>, <x2>, <p>, and <p2> for a particle in the first state of a harmonic oscillator.

2. Relevant equations
The harmonic oscillator in the first state is described by $$\psi$$(x)=A$$\alpha$$1/2*x*e-$$\alpha$$*x2/2. I'm using the definition <Q>=($$\int$$$$\psi$$1*Q*$$\psi$$)dx where $$\psi$$1 is the complex conjugate of $$\psi$$, and Q is the specific operator.

3. The attempt at a solution
I solved for <x>, and found it was zero. <p> I'll solve for in a similar fashion. However, for <x2> and <p2>, I am unsure of what operators I use. For the <x> operator, it is simply x, so for <x2>, would I use x2 as an operator?
(note that I the only superscripts here are the ones above e, I don't know why latex is putting all of my symbols so high

2. Mar 31, 2010

### kuruman

Yes, that's what you should use.

3. Mar 31, 2010

### dx

(Put the whole equation in the tex barackets instead of individual symbols)

The operator for <x²> is simply multiplication by x², so <x²> = ∫ψ*(x)x²ψ(x)dx, and <p²> is

$$-\int \psi^{*}(x) \hbar^2\frac{\partial^2}{\partial x^2}\psi(x) dx$$

4. Mar 31, 2010

### KaiserBrandon

ok, thank you so much guys. It's a good thing I have physics forum to at least make my new ventures into the realm of quantum mechanics a bit easier :)