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Homework Help: Spectrophotometry and Beer-Lamberts Law

  1. Nov 4, 2011 #1
    1. The problem statement, all variables and given/known data
    A molecule has a spectral line at 27319 cm-1

    what is its wavelength?
    what is its frequency?

    2. Relevant equations
    where A=absorbance, ε=molar extinction coefficient, C=concentration and l=path length

    3. The attempt at a solution
    thought about doing 1 over the spectral line for the wavelength, and correcting the units, but then realised frequency is 1 over the wavelength, which would just be the original answer

    If I'm honest, i am not sure what it means by a spectral line, think the question may be badly worded
  2. jcsd
  3. Nov 4, 2011 #2


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    Science Advisor
    2017 Award

    Frequency is not 1/wavelength. It's easy to see that this equation is not true by looking at the units. Frequency has units of inverse time (e.g. s-1). Wavelength has units of distance (e.g. m). 1/wavelenght does not give units of inverse time.

    Frequency is (speed of the wave)/wavelength. You can check the units to see that dividing a speed by a distance give units of inverse time.
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