The sun's rays reach Earth every day throughout the year. Among the components of the solar radiation the following types of radiation can be identified : infrared, visible and ultraviolet (UVA, UVB, UVC). The first type of radiation (infrared) is responsible for the sensation of heat and is responsible, among others, for the occurrence of sunstroke. Visible radiation allows you to see colors during the day, and after dark lets you see in shades of gray.

From the point of view of skin changes or tanning, the most interesting is ultraviolet radiation. UVA rays account for 95% of radiation that reaches the Earth and its intensity is constant throughout the year. In addition, it passes both through window panes and clouds. UVA has the ability to penetrate into the dermis and even into the subcutaneous tissue, degrading collagen and elastin fibers, which results in lowering the elasticity of the skin and the formation of wrinkles. Moreover, the UVA rays on the skin cause hyper-pigmentation, photo-allergic and phototoxic reactions. Currently, UVA rays are used in cosmetics (solaria) and dermatology (photo-chemotherapy).

The share of UVB rays in total radiation reaching the Earth is small and accounts for 5% only. The highest intensity of this radiation is between 10 and 15, especially in summer. In contrast to UVA rays, UVB radiation is blocked by windshields and clouds, but passes through water and quartz glass. UVB rays act at the level of the epidermis, have strong erythematous properties, and include sunburn. In addition, they induce immunosuppression, i.e. a propensity for viral and bacterial infections. Despite many disadvantages, UVB radiation also has a beneficial effect on humans, because it is involved in both the synthesis of skin pigment and vitamin D.

The highest energy comes from UVC radiation, which is mostly retained by the ozone layer of the atmosphere, and thus does not reach the Earth, and just like UVB radiation is stopped by the window panes. Excessive exposure to radiation may result in severe erythema or even damage to the cornea. UVC radiation has been used in bactericidal lamps due to its bactericidal and bacteriostatic properties

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