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Need of Wave Packet

  1. Feb 4, 2010 #1
    Why Schrodinger postulated that a material particle in motion is equivalent to a wave packet rather than a single wave train?
  2. jcsd
  3. Feb 4, 2010 #2


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    By "a single wave train" I guess you mean a plane-polarized wave with a perfectly precise wave vector, e.g.:

    [tex]\phi\left(x\right) = e^{ikx}[/tex]

    The problem with this function is that it has infinite extent, or infinite uncertainty in position space, as required by the HUP, since [tex]\Delta p = 0[/tex] for this choice. That means that the function is not square-integrable, and therefore is not normalizable, and cannot represent a wavefunction that is a solution the Schrodinger equation.
  4. Feb 4, 2010 #3
    I am new to quantum mechanics and have just started introductory wave mechanics so can u please explain it to me in simple terms
  5. Feb 5, 2010 #4

    Claude Bile

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    Some of this expands on Spectracats post;

    A wave-packet is a function that is spatially localised, whereas infinite wave trains continue to the ends of the universe. When we look at an experiment (single-slit diffraction for example), we know that the electrons are spatially localised in some fashion (within the lab, for example), thus we need a wave-packet to describe the position of the particle.

    Since wave-functions represent probability, thus they are mathematically constrained in that the integral over all space must = 1. To be normalisable, the integral over all space must be finite. Wave-packets possess this property, but single wave trains do not.

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