Return of the Pee Checker: You found that the original Pee Checker 9000 hydratio

Question

Return of the Pee Checker: You found that the original Pee Checker 9000 hydration meter from discussion suffered from an unfortunate flaw: corrosion destroys the electrodes in the urine sample chamber after only a few uses. You decide to design the new and improved Pee Checker 9001, which measures the concentration of the urine optically, not electrically. The Pee Checker 9001 measures the concentration of urobilin (or urochrome), the source of the yellow color of urine. When you are dehydrated, the urobilin is less diluted with water and your urine looks more yellow; when you are hydrated the urobilin is more diluted with water and your urine looks less yellow By measuring how much light is absorbed by a sample, and applying Beer's Law, we can determine the concentration of urobilin in the sample and, therefore, assess the user's hydration. 1. If urobilin solutions (and urine) look yellow, what is a wavelength of visible light that a urobilin solutions probably transmits (doesn't absorb strongly)? And what is a wavelength of visible light that a urobilin solution probably absorbs (doesn't transmit strongly)? Hint: here's absorption spectra for four colors of food coloring: Food Coloring 0.7 0.6 e 0.5 0.4 0.3 0.2 0.1 Blue Food Coloring -Red Food Coloring Yellow Food Coloning --Green Food Coloring 400 500 600 700 Wavelength (nm)

Explanation / Answer

1)

If a substance looks yellow, it means that the substance absorbs the complementary wavelength of yellow that is the purple wavelength.

From the above graph, we can see that the maximum absorbance intensity of yellow food coloring is at a wavelength of about 400-420 nm and that belongs to the purple color range.

When white light is incident on Urobilin it absorbs purple wavelength (400-420 nm) and transmits yellow wavelength (570-600 nm) which is what we observe with our eyes.

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