So NADH can absorb light that has a wavelength of 340 nm. So basically, if we have some type of solution that contains these two reactants and we place our sample of enzymes into that solution, and if this enzyme is present in that mixture, then what happens is if we begin measuring how much light is absorbed where the light has this specific wavelength value. If the absorbedance increases over time, then that means is we produce more of this product because this product is able to absorb more of that light. So once again, one property of reduced nicotine amide adenine dinucleotide, NADH, is that it has the ability to absorb light of a specific wavelength, 340 nm. Therefore, we can monitor the activity of the enzyme indirectly by examining how much light is absorbed by that solution. And this is shown in the following diagram.