Blue—the color of (pure) water

Abstract

Water can exhibit many different colors due to a variety of physical properties.Here, we focus on some observable colors within very pure freshwater. We only treat the absorption of light due to electronic and ro-vibrational excitations and scattering due to refractive index fluctuations of the water and the respective consequences for the appearance of colors.

Cherenkov radiation: why is it perceived as blue?

“…The respective change in color is mostly a change in saturation. This correlates well with the discussed colors of nearby objects in clear water in nature [21]. However, for much longer water path lengths, scattering can become prominent with respective changes in the spectra.…”

“…However, for much longer water path lengths, scattering can become prominent with respective changes in the spectra. Indeed, a deep blue color due to in-water scattering has also been observed for deep clear water hot pools in Yellowstone National Park where ground scattering was negligible [22] as well as for very long horizontal paths in very clear natural water [21]. In these cases, the incident radiation was white light.…”