I'm currently, yet again, left clueless by a problem.(adsbygoogle = window.adsbygoogle || []).push({});

See: http://idefix.physik.uni-freiburg.de/~aufgabe/QMI2004/qm3/node1.html [Broken]

Ok, so they give the Psi(x) in position space, and the first question is to give the corresponding, normalized wave equation in momentum space.

You do a fourier transform, no?

Psi(p)=Int ((1/sqrt2pi) Psi(x) (e^ipx/hbar) dx

no?

From that, I get Psi(p)=(2hbar/(p sqrt2pi)) sin (pa/hbar)

or....?

After that, I tried to get the expectation value, <p>, but with poor results. Integrate Psi* Psi p dp, yeah? What I get is 4hbar^2/(2pi p^2) [ln|p| sin^2(pa/hbar)]

Now, I know this has to be wrong, but I have no idea what I'm doing to screw it up.

I tried to do <p^2> and <x> and it just gets worse, and messier. WHAT AM I DOING WRONG??

Pleease help. Thank you :)

edit:I think I've got it! Well, at least part of it. I've gotten my expectation values for p and x to be zero, and I think my x^2 and p^2 are wrong, but... I can't think of anything else... so, it's staying right now with

<p^2>= (2hbarp*sinpa)/pi

<x^2>= A^2 (2a^3/3)

Working on the rest, still... but coming a bit further?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Expectation values in momentum/position space?

Can you offer guidance or do you also need help?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**