There is a direct relationship between absorbance and concentration is the higher the absorbance of a substance, the more concentrated its solution will be in water or another medium. In chemistry, this is a principle known as the Beer-Lambert Law.
The law measures the absorbance of a substance in a medium by determining how well light passes through it. The more heavily concentrated the substance, the less visible light passes through. The law also states that when judging the penetration of light using a spectrometer, fewer wavelengths of light, both visible and invisible, can pass through as the concentration of the substance increased.