There are those who ask "what the clouds smell" and who wonders why we see blurred under water . Both issues equally lawful and surely give for a long debate, but we, we want to answer you to the second question as clear as possible so that anyone can understand it.
Surely, once, diving without the need to do it with a diving team or a snorkeling mask, you have opened your eyes and you have only been able to see blurred shapes or even the color of the sea or the pool without hardly differentiating anything else. There is a reason that lies in the nature of the human being.
In the human eye , the lens acts for a convergent lens with which we focus on the images we receive in the retina. When a ray of light passes from a transparent medium to another, its trajectory deviates. It is the phenomenon we know as refraction . The light is refracted in the lens and projected on the retina and the lens "focus" by curving more or less.
Outside the water, with the eye in the air, the lens has a refractive index that allows us to focus the images. In the water, however, it has a refraction index similar to the lens , so that it almost stops its convergent lens function and the light rays with the images reach us to the bottom of the eye almost parallel.
What is the consequence?
the solution?Air in front of the eye, so that the lens again exerts its function as " approach lens ". Our diving mask will correct this effect as it will prevent water from touching our eye.
As curiosity add that the Phoenicians, the first navigators of which you have constancy, when they wanted
