Energy of color | Causes of Color

A page from the "Causes of Color" exhibit...

Is light tuned to our eyes?

Energy of Color

We can detect the range of light spectrum from about 400 nanometers (violet) to about 700 nanometers (red). We perceive this range of light wavelengths as a smoothly varying rainbow of colors - the visual spectrum.

It might seem remarkable that so many distinct causes of color should apply to that small band of electromagnetic radiation to which the eye is sensitive, a band less than one "octave" wide in an electromagnetic spectrum of more than 80 "octaves." So much happens in this narrow band because this is the region in which the interaction of radiation with electrons first becomes important.

Radiation at lower energies induces a relatively small motion of atoms and molecules, which we sense as heat, if at all. Radiation at higher energies has a destructive effect since it can ionize atoms, that is, completely remove one or more electrons, and can permanently damage molecules.

Only in the narrow optical region, just that region to which the human eye is sensitive, is the energy of light well attuned to the electronic structure of matter with its wide diversity of colorful interactions.