Posted: February 1st, 2023
Humans and Flat diving mask
The flat diving mask window separates the eyes fromâ€¯the encompassingâ€¯water by a layer of airâ€¯thatâ€¯helps humans visualizeâ€¯clearly underwater. While wearing the mask, the objects appears 33% magnifiedâ€¯and 25% closer.
Color vision isâ€¯a capabilityâ€¯to sense discrimination betweenâ€¯completely differentâ€¯wavelengthsâ€¯of light.â€¯Itâ€¯additionally helps in visual perception of objects; their identity and characteristics (e.g., whatâ€¯fruit it is, whether it’sâ€¯raw or not). Light gets attenuated by waterâ€¯due toâ€¯color absorption. Theâ€¯cloudinessâ€¯of the water and dissolved materialâ€¯additionallyâ€¯affects color absorption.
As shownâ€¯within theâ€¯figure, the light that is most absorbed by water is of red color, and light absorbed in smaller extent are violet, yellow, andâ€¯greenâ€¯light. So, the light that is absorbed by water in smallest amountâ€¯is of blueâ€¯color.
Colors with wavelengths like red, orange, yellowâ€¯are rapidly absorbed in water. Only the wavelengths like blue and greenâ€¯are mostly available for scattering in water as these lights can penetrate to any depth.
Underwater visibilityâ€¯isâ€¯calculated inâ€¯twoâ€¯ways which are represented as follows:
Horizontal visibility â€”â€¯to what distance one can see by lookingâ€¯straight ahead.
Vertical visibility â€”to what distance one canâ€¯seeâ€¯by lookingâ€¯up or down.
The theoretical black body visibility of pure water is estimated at seventy-four meters. This estimation is based on the optical properties of water for a 550 nm wavelength light. Inâ€¯terriblyâ€¯clear water, visibilityâ€¯mightâ€¯extend as muchâ€¯asâ€¯toâ€¯80 meters.
There areâ€¯threeâ€¯importantâ€¯factors thatâ€¯influenceâ€¯underwater visibility:
â€¢ Light penetration
The intensity (ofâ€¯light)â€¯thatâ€¯penetrate the surface of water depends onâ€¯3â€¯factors: overall level of light (a sunny versus a cloudy day), theâ€¯roughness of the surface, and the angle atâ€¯whichâ€¯the rays meet the water.
The position of Sunâ€¯additionallyâ€¯affects the penetration power ofâ€¯light, withâ€¯the best levels ofâ€¯light at noon. The Sunâ€¯further sinks on the horizon; the angle of incidence is smaller,â€¯and the visibility is poor.
â€¢ Biological species
Decreased visibility in underwater could also be due to too much light, as large amount of light leads to plankton blooms or algae blooms and causes change in the color of water surface. Plankton bloom is due to the rapid increase in the population of microscopic plants (like algae) in sunlit layers of the ocean. This can reduce the visibility to less than 3 meters.
Particulatesâ€¯likeâ€¯suspended sand and silt carried by running water affects visibility underwater. These particlesâ€¯scatter and absorbâ€¯light,â€¯leading toâ€¯reduced visibility.
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