Water is a coloring substance slightly bluish. Unlike what we've learned, water is not colorless. It's true that when we look at water in a glass, it looks transparent, but have you ever noticed the coloration of deep water like rivers or seas? Check out this article for an explanation of the differences in the color of this very important liquid.
Lookalso: radiation and matter
Water color and light absorption
The bluish hue of the water originates from the light absorption that focuses on her. Water tends to absorb wavelengths better longer light, like the tones Orange and Red.Electromagnetic waves in minors lengths and, consequently, higher frequencies, such as bluish tones, they are notabsorbed by water and end up being partially reflected (the term scattering of light is common in this case). The set of wavelengths that a body or substance tends to absorb when illuminated is called the absorption spectrum.
In the figure above, it is possible to observe the light rays being scattered into the water.
About visible radiation, water is a very transparent substance, that is, light propagates inside it without suffering major absorptions, and that's why the blue hue of the water can only be seen in big onesdepths.
Lookalso: the color of light
When light travels small distances inside the liquid medium, it is not able to absorb significantly none of the colors of the visible spectrum, as in the case of water when placed in a glass.
water is not capable of issue any kind of visible radiation, just absorb it or reflect it. That's why we say water is a secondary source of light. This property indicates that the color of water depends on the light that falls on it. Therefore, if the lightWhite travel considerable distances in the aqueous medium, this medium will present bluish tones, due to the absorption of orange and red colors. If you want to understand more about the process of absorptiongiveslight and its relationship with the color of objects, access the article The colors and frequency of light.
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You may have also noticed that when the water is moving, such as waves breaking on the beach or on the crests of waves, its color tends to turn white. This is because there are dilution of airatmospheric between the water molecules, further slowing the light absorption process. The reduction in the light absorption process makes the reflection phenomenon more evident: as all colors are reflected equally, water has light tones, close to white. Watch:
When water is stirred, atmospheric gases are trapped inside. This process decreases the water's ability to absorb light.
Ice cubes tend to turn white inside by a process similar to moving water: water starts to freeze from outsideforinside, trapping impurities and atmospheric gas molecules diluted in their content in the central region. As it is the last to freeze, this region has a milky appearance. One way to make clear ice is to boil the water before freezing it, which will partially remove the diluted gas.
By Rafael Hellerbrock
Graduated in Physics
Would you like to reference this text in a school or academic work? Look:
HELERBROCK, Rafael. "What color is the water?"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/qual-cor-agua.htm. Accessed on June 27, 2021.
