20/05/2021
Sunglasses😎
The first sunglasses were used by the inhabitants of the Far North and consisted of pieces of tree bark and other materials with narrow slits for the eyes cut into them.
❤ Colored glasses
The first to use smoky glasses were the Chinese. To which there is a reference in "Notes on Leisure Hours" by Liu Chi . The glasses were made of smoky quartz. But in the beginning, such glasses were used not to protect the eyes from the sun, but by the judges to hide their attitude to the verdict during its announcement.
Colored glasses serve to protect the eyes from too bright light. Previously, they used green glasses, but since then, as it turned out that they, passing the brightest rays of the spectrum, reach the goal least of all, they began to use gray and blue glasses. Gray smoky glasses absorb all colored rays almost equally; blue glasses most of all block yellow and orange rays (the brightest). Spherical, cylindrical and prismatic are also colored.
❤ Glasses with plastic lenses
Plastic colored lenses are more comfortable and safer than glass lenses, especially during outdoor activities. It is assumed that the plastic has layers that reflect or absorb ultraviolet light. However, most often they use cheap plastics that transmit ultraviolet radiation. These glasses cannot be called sunglasses. They exacerbate the harmful effects of ultraviolet radiation, that is, they cause more damage to the eye than none at all. The aggravating effect is associated with the fact that the darkening in the visible region leads to the dilation of the pupil, and a larger amount of ultraviolet radiation penetrates into the dilated pupil, than into the unexpanded one, without glasses. In this regard, when buying sunglasses with plastic lenses, you need to require verification of their effectiveness in the UV range.
❤ Hole glasses made of dark plastic. Perforated glasses
The northern peoples had a kind of "sunglasses" to prevent snow blindness. It turned out that this type of perforated glasses can be used to correct myopia. It is known that when viewing through a small hole (for example, an iris diaphragm), the smaller the hole diameter, the greater the depth of field. A person can get an image of acceptable quality even without a lens (see camera obscura). Perforated glasses are a set of small holes in a dark matrix. These glasses have a drawback - they cannot be worn all the time, as binocular vision may deteriorate. Correct wearing of these glasses can help to relax (rest) the eye muscles.❤
