1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Beer-Lambert Law; Fraction of hemoglobin

  1. Mar 20, 2009 #1
    1. The problem statement, all variables and given/known data

    A "pulse oximeter" operates by using light and a photocell to measure oxygen saturation in arterial blood. The transmission of light energy as it passes through a solution of light-absorbing molecules is described by the Beer-Lambert law, given below, which gives the decrease in intensity I in terms of the distance L the light has traveled through a fluid with a concentration C of the light-absorbing molecule.

    I = I010-εCL or log10(I / I0) = -εCL

    The quantity ε is called the extinction coefficient, and its value depends on the frequency of the light. (It has units of m2/mol.) Assume the extinction coefficient for 660-nm light passing through a solution of oxygenated hemoglobin is identical to the coefficient for 940-nm light passing through deoxygenated hemoglobin. Also assume also that 940-nm light has zero absorption (ε = 0) in oxygenated hemoglobin and 660 nm light has zero absorption in deoxygenated hemoglobin. If 31% of the energy of the red source and 80% of the infrared energy is transmitted through the blood, what is the fraction of hemoglobin that is oxygenated?


    2. Relevant equations

    I = I010-εCL or log10(I / I0) = -εCL

    3. The attempt at a solution

    I have no idea how to even approach this...this is non-calculus based physics. I know that I am solving for the concentration and that the length and e cancel out...besides that. I keep getting the same wrong answer of 24.7%.
     
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted



Similar Discussions: Beer-Lambert Law; Fraction of hemoglobin
  1. Poiseuille's law (Replies: 0)

  2. Biot-Savart law (Replies: 0)

  3. Law of Poles (Replies: 0)

Loading...