Can we see well underwater? Yes or not let’s check.
Tribals gipsies and aboriginals our vanishing lot. Modern society has marginalised them. They walk and talk differently, do not conform to our ways of life, occupy territory that we need by badly for our needs and development – the cards are all against them. Yet, they have some special talents and ways that we can take cues and learn to use to advantage, if only we treat them well and attempt to understand them.
The Nari Kauravas are expert foresters and foragers the Bhils are experts in what we call a sustainable way of life; they make useful things from leaves, roots, suits, and box and materials from small game animals. Some tribes are expert metallurgists while some others find medical use in many a herb and shrub. These are discoveries, crafts and skills that they have learnt power generations of living as one with nature skills and innovations that modern man can admire and learn from.
A recent example of underwater comes from the work of Dr Anna Gislen and works of the University of Lund in Sweden. This has to do with the remarkable ability of the tribes collectively called as Moken people. These are wandering she dwellers who have been the first inhabitants of the Andaman coastal regions of India, Myanmar, Thailand and Malaysia.
They are related to the others gipsies of the Island archipelagos all the way to the Philippines. Some believe that it is the ancestors of the Moken who drew the cave paintings of the Phang Nga Bay and other places.
For 8 months of the year, the Moken live of the sea, foraging dear existence from its exploiting and an amazing number of organism therein. They use nets traps, Spears and harpoons and spend a lot of time diving and staying underwater. No snorkel, no sea googles, no air cylinders, or flippers for them they make do as is, or at best use primitive gear. During the monsoon season, demu Mysore and live in temporary thatched huts, trading with the local people.
It is the dear extraordinary ability to see underwater that impressed doctor Gislen, the science they are able to do what ordinary people cannot and do so with no special equipment. They simply dive into the water collect items and haul them up. How can they see underwater too well while we cannot?
We do not see clearly underwater, all went well in our eyes. the reason is that the eye has two refracting materials that bend and focus light into the retina. these are the convex-shaped cornea at the surface of the Eye and the global lens which is located a bit interior. When light travels in the air and hits the cornea, it is bent because the cornea is curved and has a refractive index of 1.34, violet date of air is the standard value of 1.0.
The so bent light now falls on the lens, a transparent plastic, elastic, egg-shaped gel that is held in place by a bunch of fibres attached to the clear muscles. The lens changes its refractive power efficiently, depending on its shape the light focus by the lens falls on the retina and we see a sharp image.
The variable refractive index of the lens is useful since it is this feature that helps us see both distant and near objects sharply. When the ciliary muscles contract and loosen the fibres, the lens assumes a ball-like shape helping in to focus near objects. When the ciliary muscles are relaxed, the fibres tighten and the lens flattens to help focus for objects. ( It is for this reason that we are advised not to read in a moving bus or train. The ciliary muscles have to work overtime, constantly adjusting the focal length of the lens to help us c sharp and they Tyre and your eyes ache ).
This adjustment for variable focusing is referred to as accommodation and is a vital requirement not only for us but for other animals and birds. Diving birds like the heron are champions at it, The turtle not bad at all, while the wise owl fares poorly here.