You have probably looked at water surfaces and noticed that they appear blue, both on maps and in real life. But have you ever asked yourself why they appear so?
In this article, Kenyans.co.ke delves into the science behind the blue appearance of some water surfaces. Understanding this phenomenon requires us to explore the way light interacts with water molecules.
Beyond the natural bodies of water, even swimming pools are often designed to appear blue, with the help of specific materials and additives. The same principles of light absorption and reflection apply to pools, enhancing the visual effect and making them appear even more inviting.
Oceans and Large Water Surfaces
According to the National Oceanic Service, the ocean surface appears blue mainly because water absorbs colours in the red part of the light spectrum, acting as a filter, thereby leaving behind colours in the blue part of the spectrum for you to see.
"The ocean looks blue because red, orange and yellow (long wavelength light) are absorbed more strongly by water than is blue (short wavelength light). So when white light from the sun enters the ocean, it is mostly the blue that gets returned. Same reason the sky is blue." Scientific American adds the explanation behind the water's surface's appearance.
Some people have also argued in the past that the blue colours of the ocean waters and swimming pools are due to the blue sky’s reflection on the surfaces.
In other words, the colour of the ocean and the colour of the sky are related but occur independently of each other. In both cases, the preferential absorption of long-wavelength (reddish) light gives rise to the blue appearance.
Swimming Pools
The above light principles also apply to the blue appearance of swimming pool water surfaces, however, some pool bottoms are also built using blue titles, giving them the blue appearance.
Rivers and Streams
However some water surfaces especially rivers appear brown or reddish instead of the normal blue appearance.
The brown appearance of rivers is because the water is constantly moving, hitting rock surfaces and bottoms, in the process generating mud that in return makes the water appear so.
The scenario is also exhibited in some water surfaces appearing green. The green colour according to scientists, is a result of impurities such as algae and other water plants.
The two scenarios for green and brown appearance are because the impurities overwhelm the water's natural blueness.
Ocean Bottoms
However, images and videos taken at ocean bottoms suggest that the water appears partially or completely dark. This is probably the reason why deep sea divers and other rescue operations use lights to access the bottom parts.
The dark appearance is mostly because of the depth in the oceanic bottoms where light hardly penetrates depths beyond 656 feet and no light even reaches depths reaching 3,280 feet, according to the National Oceanic Service.
