Sunlight breaks down upon reaching the earth’s surface in various types of radiation according to wavelength, are classified as ultraviolet radiation, visible radiation and infrared. In turn, ultraviolet radiation can be UVC, UVB or UVA. UVC rays have the shortest wavelength, are the most energy and therefore more capable of burns, but are retained by the ozone layer. Thus the reduction or the existence of holes in the ozone layer is so dangerous.
UVB rays as well as the heating effect (which causes the redness or Erythema of the skin when exposed to sunlight), penetrate the epidermis and stimulate the melanocytes (skin cells that produce melanin, the substance that gives the brown color to the skin).
UVA rays are the most penetrating the skin and are the cause of skin aging and melanoma (skin cancer).
Besides the type of radiation, it is necessary to know the factors influencing the action of sunlight on the skin. Thus, we must bear in mind that, how much higher the geographical area where we are, the more intense the exposure, the obliquity of the rays of the sun and the earth also influences, depending on the season, time of day and the latitude of the geographical area. The climate also influences, as the rain and clouds absorb some radiation. Also the type of area where we are, because the snow reflects up to 85% of the rays, and the dry sand to 17%.
