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 (638 nm) and an infrared (974 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.

Answer 1

`4.70\cdot 10^(14) Hz, 3.08\cdot 10^(14) Hz`

Step-by-step explanation:

The frequency of a light wave is given by:

`f=(c)/(\lambda)`

where

`c=3.0\cdot 10^8 m/s` is the speed of light

`\lambda` is the wavelength

For the red light emitted by the diode,

`\lambda = 638 nm=6.38\cdot 10^(-7)m`

So, the frequency is

`f=(3.0\cdot 10^8 m/s)/(6.38\cdot 10^(-7) m)=4.70\cdot 10^(14) Hz`

For the infrared light emitted by the diode,

`\lambda = 974 nm=9.74\cdot 10^(-7)m`

So, the frequency is

`f=(3.0\cdot 10^8 m/s)/(9.74\cdot 10^(-7) m)=3.08\cdot 10^(14) Hz`