Oxygenated hemoglobin absorbs weakly in the red (hence its red color) and strong

Question

Oxygenated hemoglobin absorbs weakly in the red (hence its red color) and strongly in the near infrared, whereas deoxygenated hemoglobin 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 persons finger and has two light-emitting diodes --a red (640 nm) and an infrared (905 nm)-- and a photocell that detects the amount of light transmitted through the finger at each wavelength. (a) Determine the frequency of each of these light sources. Red Hz Infrared Hz (b) If 68% of the energy of the red source is absorbed in the blood, by what factor does the amplitude of the electromagnetic wave change? [Hint: The intensity of the wave is equal to the average power per unit area as given by the equation given below.]

Explanation / Answer

here,

w1 = 640nm = 640 * 10^-9 m
w2 = 905 nm = 905 * 10^-9 m

wavlength = speed of light / frequency
therefore
F = C / W

A)

F1 = (3*10^8) / (640 * 10^-9)
F1 = 4.6875 * 10^14 Hz

F2 = (3*10^8) / (905 * 10^-9)
F2 = 3.3149 * 10^14 Hz

B)

as energy of wave is directly proportional to square of amplitude therefore

Amplitude = sqrt(1 - 0.68)
amplitude = sqrt(0.32)
amplitude = 0.565 m

Related Questions

Navigate

• Browse (All)
• Browse O
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.