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Homework Help: Finding fourier transfrom of the following wavefunction

  1. Jun 20, 2005 #1
    Let Psi(x,0)=E^(ik0x) when x=(-a/2,a/2) and zero elsewhere.

    Can this be a wavefunction of a free particle. I belive it is so because every function of x can be expressed as a wavepacket. Is this correct?

    If I want to calculate P(x,0), probability to find the particle between x, x+dx it's just the square of the modulus. But what about P(k,0)? I'm having trouble calculating it's fourier transform, I think that the delta function must show somewhere but I don't know how.

    k seems to be certain k=k0 , right? However, P(x,0)=1/a is the same everywhere.
  2. jcsd
  3. Jun 20, 2005 #2


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    If k_0 is one definite value, then the particle has one precise momentum. What does the uncertainty principle say about the position of such a particle?
  4. Jun 21, 2005 #3


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    Is the wavefunction normalizable...?It is a generalized eigenfunction of the Hamiltonian...?

  5. Jun 21, 2005 #4
    Yes it is normalizable. But it's not a generalized function of the Hamiltonian, is it? It's a particular case where k=ko.

    I'm asked to draw P(x,0) and P(k,0) and find out delta(x) and delta(k) and justify it using Heisenberg's uncertainty principle.

    By doing Psi's Fourier transform I get a complicated function and I don't know if that's the way I can justify the following: we know nothing about the position (cause all probabilities are the same) but k is certain.
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