When I place a working flashlight behind my hand, I see my hand bright red because of the light. So my question is, why do I only see red light after transmission even if incoming light from the flashlight is white? Can we explain these phenomenon mathematically?

Do the coefficients of absorption and transmission come in picture? If so, can you explain how? And can we measure them? Or going in more details can we explain it by using photon theory?


Your observation is linked to the "Optical window in biological tissue".

Like you already suspected, the absorption of blue light in tissue is higher than the absorption for red light.

Best read the related wikipedia article, where all relevant effects are nicely illustrated. http://en.wikipedia.org/wiki/Optical_window_in_biological_tissue

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    $\begingroup$ Plus, the hand spectrum can found here: photobiology.info/PhotobioInArt.html. $\endgroup$ – Keep these mind Jul 9 '14 at 13:04
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    $\begingroup$ thank you very much for valuable reply. Just a little doubt since in absorption spectra due to blood, water, melanin etc there are different spectral lines,while oxyhemoglobin only shows absorption line near red light wavelength(about 650nm). So can we say like oxyhemoglobin is the second dominant factor in the tissues?. after water since water is nearly transparent for visible light. $\endgroup$ – dking Jul 9 '14 at 13:12
  • $\begingroup$ For the range of visible light the appearance of tissue is well-described by the scattering of light by cell structures, and by absorption of this diffuse light by the hemoglobin molecules. Hbo2 contributes a bit more to the red appearance than Hb, since the first one has even lower absorption in the red. Water does't play a role at visible wavelengths, as it starts to absorb only in the near infrared. $\endgroup$ – a.j. Jul 9 '14 at 14:09
  • $\begingroup$ Is there any mathematical model explaining the absorption and transmission phenomenon?? that will be better for project writing. $\endgroup$ – dking Jul 9 '14 at 14:36

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