Most birds are tetrachromatic, possessing four types of cone cells each with a distinctive maximal absorption peak.
Water in the liquid state possesses many molecular interactions that broaden the absorption peak.
These crossover peaks can be quite strong, often stronger than the main saturated absorption peaks.
The absorption peaks of chlorophyll a are at 665 nm and 465 nm.
S has an absorption peak of 425 nm with a tail extending into blue light.
Instead, they found two very sharp absorption peaks, a seemingly unexplainable phenomenon.
It has two absorption peaks, 310 and 340 nm.
The absorption peak appears to flatten because close to 100% of the light is already being absorbed.
The result is presented as an absorption peak, and quantified using bespoke software.
At very high frequencies (such as X-rays) the refraction decreases again, because you are on the other side of the absorption peak.