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 person's finger and has two light-emitting diodes --a red (645 nm) and an infrared (940 nm)-- and a photocell that detects the amount of light transmitted through the finger at each wavelength.

Explanation / Answer

a). frequency of RED=v/wavelength=3*10^8/645nm=4.65*10^14Hz

frequency ofInfrared=3*10^8/940nm=3.19*10^14Hz

b).I2 = I1-.63I1 = 0.37 I1.................

Emax =sqrt I..........(E2-E1)*100/E1

= (sqrtI2-sqrtI1)*100/sqrtI1

= 39.1 percent

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