Oxygenated hemoglobin absorbs weakly in the red (hence its redcolor) and strongly in the near infrared, whereas deoxygenatedhemoglobin has the opposite absorption. This fact is used in a\"pulse oximeter\" to measure oxygen saturation in arterial blood.The device clips onto the end of a person's finger and has twolight-emitting diodes—a red (632 nm) and an infrared (930 nm)—and aphotocell that detects the amount of light transmitted through thefinger at each wavelength.
(a) Determine the frequency of each of these light sources.
red Hz
infrared Hz
(b) If 66% of the energy of the red source is absorbed in theblood, by what factor does the amplitude of the electromagneticwave change? Hint: The intensity of the wave is equal to theaverage power per unit area as given by I = Emax2 2ĂŽÂĽ0c = c 2ĂŽÂĽ0Bmax2.
