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Homework Help: Wavelength/Frequency short Questions help

  1. Mar 21, 2010 #1

    For a) I did frequency = speed of light / wavelength = 3.75x1014Hz
    for b) I did 3.75x1014Hz x 10-15s=0.375
    I think a) is right, but I don't know about b)
    For c) I would have thought it is the same frequency as the first because I am taking it as if it is the same frequency, but a shorter amount of time, but I think this is wrong.

  2. jcsd
  3. Mar 21, 2010 #2
    anyone please?
  4. Mar 21, 2010 #3


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    Homework Helper

    10^-15 s is one femtosecond, not 20.

    Have you tried the energy-time uncertainty principle?
  5. Mar 21, 2010 #4
    Oh right, so I guess b) would be what I put times 20, so 7.5...
    c) If that has anything to do with heisenberg's uncertainty principle, we haven't been taught that in this class, is there another way?
  6. Mar 21, 2010 #5
    Or if I use that which equation should I use? I looked at it, but I'm not sure how it applies.
  7. Mar 21, 2010 #6
    Hm I looked at the equations, and have found that [tex]1/2\delta T = 2.5x10^{13}hz[/tex] where delta T = 20 femtoseconds...is this correct?
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