Every day, you will be exposed to the sun, including visible light, infrared light and ultraviolet light. But don't think that there is no ultraviolet light without the sun, as long as there is light, there must have these three types of light, including the fluorescent lamp used indoor. According to the difference of wavelengths, the three kinds of light are distinguished. The ultraviolet light has the shortest wavelength but the energy is the strongest. The wavelength is between 10nm and 400nm. The infrared wavelength is over 700nm. These two kinds of light are not visible to the human eye, but they are important sources of the earth which can be affected the operation of the entire ecosystem. Excessive ultraviolet light also has certain damage to humans, not only causes skin aging and skin cancer when it is serious but also results in damage to the eyes; but many people may ignore and it is easy to let the eyes get early degraded.The difference wavelength in ultraviolet are divided into UVA (320 – 400nm), UVB (280 – 320nm) and UVC (100 – 280nm). The following are detailed:
UVA – About 95% of UV rays are UVA, which has strong penetrating power. It can penetrate clouds, glass, indoors and cars, and can reach the dermis layer, causing melanin precipitation to bring on sunburn, skin aging and spots. UVA can be subdivided into UVA-1 (340 – 400 nm) and UVA-2 (320 – 340 nm):
UVA-1 – A long-wave range with the strongest penetrating power and the most harmful to the skin. It is important to note that UVA-1 is weak in non-summer season but still exists. For long-term exposure and accumulate, the skin loses its elasticity, aging and relaxation, wrinkles and a large amount of melanin precipitation.
UVA-2 – Relatively deep in penetrating power and harmful to the skin, compare to UVB. In general, sunburn becomes red and painful, and age spots are mainly caused by UVA-2.
UVB – When UV rays reaching the surface, UVB accounts for about 2% - 5%, easy to cause immediate sunburn, initial redness and itching, severe swelling and pain to form blisters; make the skin dull and dull, causing damage to the eyes with Ophthalmitis, the eyes become drier. Although UVB is stronger than UVA, it is easier to protect because some parts of UVB are absorbed by the ozone layer.
UVC – UVC can reach the surface very small, as we know, the shorter the wavelength of ultraviolet light, the stronger the energy. But most of the UVC will be isolated by the ozone layer, only small amount will enter the surface. But in recent years, the ozone layer is continuously destroyed, more and more UVCs have reached the surface, the damage to the human body has increased year by year. How to protect UVC has gradually attracted people's attention.
Ultraviolet light has a very important value – Ultraviolet INDEX (UVI), which refers to the international measurement of ultraviolet radiation intensity at a certain point on a certain day. We will also see this index in the weather report. The safe range of ultraviolet radiation is used to remind people to avoid excessive exposure and produce lesions. As the best indicator of invisible killer, the higher the UVI value, the greater the risk of skin exposure to ultraviolet light. According to China National Meteorological Administration, based on the effect of ultraviolet light to human health. It’s divide the UVI into 0-15 grades, then the different UVIs are divided into 5 categories, namely: micro-level, low-level, medium-weight, over-grade and dangerous, providing sunburn time and recommended protective measures for public reference: