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Homework Help: The fomula h/lambda is this for the photon only?

  1. Feb 25, 2006 #1
    the fomula [tex]\frac{h}{\lambda}[/tex]

    is this for the photon only? or can it be applied to relativistic electrons too?
  2. jcsd
  3. Feb 25, 2006 #2
    it applies to particles with zero rest mass. Hence it wont apply to relativistic electrons.
  4. Feb 26, 2006 #3
    so for relativistic electrons, if I wanted it's speed, i'd use .5mv^2?
  5. Feb 26, 2006 #4
    1/2 m v^2 only works for non-relatavistic speeds, the energy for a relatavistic particle is different. See here for more details.
  6. Feb 26, 2006 #5
    Same question was asked by de Brolie. And actually, it turned out that it will.
  7. Feb 26, 2006 #6
    Yes, but UrbanXrises' original formula was either a typo or assumed that c=1. With c=1 this formula is, in fact, only good for massless particles. DeBroglie's relationship involves the speed, which is less than c.

  8. Feb 26, 2006 #7
    No, it comes from:
    [tex]E = pc = \frac{hc}{\lambda}[/tex]
    where c's cancel, and de Broglie's equation relates momentum and wavelength.
  9. Feb 26, 2006 #8
    :redface: I was thinking of the energy equation. Sorry! (Ahem!)

    Even though I got my c's wrong, the argument still holds...E=pc only hold for massless particles, which was what I was trying to say.

    Last edited: Feb 26, 2006
  10. Feb 26, 2006 #9
    so [tex]p=\frac{h}{\lambda}[/tex] is for massless particles

    but what about [tex]E=fh[/tex]?

    is this equation for massless particles too?
  11. Feb 26, 2006 #10
    No. This equation is good for anything. Basically this equation simply expresses the quantizability of energy.

  12. Feb 27, 2006 #11
    No, it applies to all particles! That's the backbone for Schrödinger equation!
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