As nouns the difference between wavelength and absorbance

is that wavelength is the length of a single cycle of a wave, as measured by the distance between one peak or trough of a wave and the next; it is often designated in physics as λ, and corresponds to the velocity of the wave divided by its frequency while absorbance is a logarithmic measure of the amount of light that is absorbed when passing through a substance; the capacity of a substance to absorb light of a given wavelength; optical density.