Pigments interact with light by selectively absorbing certain wavelengths while reflecting others. This selective absorption is what determines the color we perceive.
How Pigments Absorb Light
When light strikes a pigment, the pigment's molecules absorb specific wavelengths of light. This absorption process happens at a subatomic level. As stated in one source, "When a pigment absorbs a photon of light, it becomes excited, meaning that it has extra energy and is no longer in its normal, or ground, state". This excitation involves an electron jumping to a higher-energy orbital further from the nucleus. The wavelengths of light not absorbed are reflected, and these reflected wavelengths determine the color we see. For example, a red pigment absorbs most wavelengths except for red, which it reflects.
Several sources highlight this selective absorption:
- Plants and other photosynthetic organisms: Utilize a variety of pigments to absorb different wavelengths of light, maximizing energy capture. (MIT News)
- Retinal pigments: Absorb light within a specific range (700 nm to 400 nm), which corresponds to visible light. (Biology LibreTexts)
- Color creation: Pigments are created by modifying which colors are absorbed. By absorbing certain frequencies of light, they remove them from the reflected light, resulting in the perceived color. (HowStuffWorks)
The Molecular Basis of Pigment Color
The specific wavelengths a pigment absorbs are determined by its molecular structure. The arrangement of atoms and electrons within the pigment molecule influences which energy levels electrons can jump to upon light absorption. This is further explained by the statement, "So in short, it's all based on how molecules absorb light, so those wavelengths of light will be absorbed." (Reddit - askscience)
Practical Examples
- Photosynthesis: Chlorophyll, a green pigment in plants, absorbs red and blue light efficiently for photosynthesis, reflecting green light.
- Paints and dyes: Artists use pigments to create colors by mixing pigments with differing absorption properties.
- Color perception: Our eyes contain pigments that absorb specific wavelengths of light, allowing us to see color.
