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Ultraviolet (uv) light of knowledge
UV(Ultraviolet).Ultraviolet wavelengths of the electromagnetic spectrum is the floorboard of the radiation from 10 nm to 400 nm, ultraviolet (UV) is invisible to the naked eye.
Ultraviolet (uv) based on wavelength can be divided into: UVA, nearly far ultraviolet UVB and super short ultraviolet UVC. Ultraviolet radiation to human body skin penetration degree is different. Ultraviolet light is, the longer wavelength, the greater the damage to human skin. Shortwave ultraviolet ray can be through the dermis, medium wave can into the dermis.
A, is not visible in the daylight high-energy ultraviolet light. According to the different wavelength ultraviolet itself, the ultraviolet ray can be divided into three regions. The short-wave ultraviolet ray, uvb rays and uva rays.
1, short-wave ultraviolet ray: UVC for short. Is one of 200-280 nm wavelength ultraviolet light. Shortwave ultraviolet ray after the stratosphere of the earth's surface is absorbed by the ozone layer. Can't reach the surface of the earth, have important role to the human body. Therefore, the short-wave ultraviolet should cause enough attention.
2, UVB rays: referred to as "UVB rays. Is 280-320 nm ultraviolet wavelengths. Uvb rays on human skin has certain physiological function. Such a great part of the ultraviolet ray is absorbed by the skin epidermis, cannot penetrate into the skin. But due to the order is higher, can produce a strong light damage to the skin, by exposure site dilated vessels in the dermis, the skin can appear the symptom such as swelling, blisters. Irradiation for a long time the skin will appear red spot, inflammation, skin aging, severe cases can cause skin cancer. Uvb rays also known as uv sunburn (red), is should focus on the prevention of ultraviolet waveband.
3, UVA rays: UVA for short. Is 320-400 nm ultraviolet wavelengths. Uva rays penetrating of clothing and human body skin is much better than uvb rays, can reach the depths of the leather, and we can work on parts of the epidermis melanin, causing skin melanin, make the skin to blacken, played the defence ultraviolet ray, protect the skin. So long wave ultraviolet ray also known as the "tan". Uva rays can not cause acute inflammation of the skin, but slow, the function of the skin can be accumulated for a long time, is one of the reasons that cause skin aging and serious damage.
Therefore, to prevent ultraviolet radiation to human body skin damage, the main is to prevent the UVB exposure to the sun's ultraviolet rays; And prevent UVA ultraviolet ray, it is to avoid tanning.
B, depending on the biological effect, turn the uv wavelength is divided into four bands:
1, UVA wavelengths, wavelength of 320 ~ 400 nm, also known as long wave ultraviolet light shading effect. It has a strong penetration, can penetrate most transparent glass and plastic. Sunlight contains more than 98% of UVA rays can penetrate the ozone layer and the clouds reach the surface of the earth, UVA can direct the dermis of skin, destruction of elastic fibers and collagen fibers, to our skin. 360 nm wavelength ultraviolet UVA conforms to the phototaxis of insects response curve, trap lamp can be made up. 300-420 nm wavelength ultraviolet UVA can completely by the visible light through the special colored glass tubes, only radiation out of the 365 - nm centered near ultraviolet light, can be used for mineral identification, stage decoration, yanchao etc.
2, UVB wavelengths, wavelength of 275 ~ 320 nm, also known as the medium wave ultraviolet erythema effect. Medium penetration, its wavelength shorter part will be absorbed by transparent glass, most of uvb rays in sunlight is absorbed by the ozone layer, only less than 2% can reach the surface of the earth, in summer and in the afternoon will be particularly strong. UVB rays have erythema effect to human body, can promote the formation of mineral metabolism and vitamin D in the body, but long-term or excessive exposure can make skin, and cause swelling peeling.
3, UVC wavelengths, wavelength of 200 ~ 275 nm, also known as short-wave ultraviolet sterilization. It the penetrating power of the weak, cannot penetrate much of the transparent glass and plastic. Sunlight contains short-wave ultraviolet almost completely absorbed by the ozone layer. Shortwave ultraviolet radiation to human body harm is very big, short time radiation can burn the skin, long or high strength still can cause skin cancer. Ultraviolet germicidal lamp is UVC short-wave ultraviolet radiation.
4, UVD wavelengths, wavelength of 100 ~ 200 nm, also known as vacuum ultraviolet light.