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Homework Help: Where did I go wrong?

  1. Nov 28, 2005 #1
    What is the wavelength, k, corresponding to a frequency, w, of 7x10^19 Hz of electromagnetic wave in free space? The speed of light is 2.99792x10^8 m/s. Answer in units of m.
    I set w/k=c
    Plugging in (2*pi*7X10^19) for w, and 2.99792x10^8 for c, I got 1.467X10^12. The answer is wrong. Where did I go wrong?
  2. jcsd
  3. Nov 28, 2005 #2

    Doc Al

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    Staff: Mentor

    For one thing, the wave equation is [itex]c = f \lambda[/itex]. The frequency is in given in Hz; the wavelength (not wave number) has units of meters.

    PS: Don't confuse wavelength with the wave number (k), which is generally defined as [itex]k = 2 \pi / \lambda[/itex]. If you want the wave number, then using [itex]k = \omega / c[/itex] will work.
    Last edited: Nov 28, 2005
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