According to the biological effect, the ultraviolet light is divided into four bands according to the wavelength: long wave UVA, medium wave UVB, short wave UVC, vacuum wave UVD. The longer the wavelength, the stronger the penetration.
UVA:
Long-wave UVA, with a wavelength between 320 and 400 nm, is also known as the long-wave black spot effect. It has a strong penetrating power and can penetrate glass, even 9 feet of water; and it is present all year round, whether it is cloudy or sunny.
Degree of damage to the human body: More than 95% of the UV rays exposed to daily skin are UVA, so it is the most harmful to the skin. UVA can attack the dermis through the epidermis, causing the skin's collagen and elastin to be severely damaged; and the dermal cells have poor self-protection ability, and a small amount of UVA can cause great damage. Over time, the skin produces problems such as slack, wrinkles, and microvascular emergence. At the same time, it activates tyrosinase, resulting in immediate melanin deposition and new melanin formation, which darkens the skin and lacks luster. UVA causes long-term, chronic and long-lasting damage, which causes the skin to age prematurely, so it is also called aging rays.
Application field: UVA ultraviolet light of 360nm wavelength conforms to the phototaxis reaction curve of insects, and can make trap light. UV-AUV at a wavelength of 300-420 nm can pass through a special colored glass tube that completely cuts off visible light, and emits only near-ultraviolet light centered at 365 nm. It can be used in ore identification, stage decoration, banknote verification and other places.
UVB:
Medium wave UVB, wavelength between 275 ~ 320 nm, also known as medium wave erythema effect ultraviolet. Medium penetration, its shorter wavelength is absorbed by transparent glass, and most of the medium-wave ultraviolet rays contained in sunlight are absorbed by the ozone layer, and less than 2% can reach the surface of the earth, which is particularly strong in summer and afternoon.
Degree of harm to the human body: It will oxidize the protective lipid layer of the epidermis and dry the skin; further denature the nucleic acids and proteins in the epidermal cells, causing acute dermatitis (ie sunburn) and other symptoms, and the skin will turn red. It hurts. In severe cases, such as prolonged exposure, it can easily lead to skin cancer. In addition, long-term damage to UVB can cause variability in melanocytes, causing sun spots that are difficult to eliminate.
Application areas: UV health lamps, plant growth lamps are made using special transparent purple glass (not through the light below 254nm) and phosphors with peaks around 300nm.
UVC:
Short-wave UVC, with a wavelength between 200 and 275 nm, is also known as short-wave sterilization UV. It has the weakest penetration and cannot penetrate most of the transparent glass and plastic. The short-wave ultraviolet light contained in sunlight is almost completely absorbed by the ozone layer and is absorbed by the ozone layer before reaching the ground.
The degree of harm to the human body: The UVC in nature is absorbed by the ozone layer because it has not reached the ground, and the impact on the skin can be neglected. However, the short-wave ultraviolet rays are very harmful to the human body and cannot directly illuminate the human body. If it is directly irradiated, it can burn the skin in a short period of time, and long-term or high-intensity irradiation can cause skin cancer.
Application field: UVC germicidal lamp emits UVC short-wave UV. Short-wave UV is widely used in hospitals, air conditioning systems, disinfection cabinets, water treatment equipment, water dispensers, sewage treatment plants, swimming pools, food and beverage processing and packaging equipment, food factories, cosmetics factories, dairy products, wineries, beverage factories, Areas such as bakeries and cold rooms.
Advantages and disadvantages of ultraviolet light
In general, the advantages and disadvantages of UV:
Advantages of ultraviolet light: 1) disinfection; 2) promotion of bone development; 3) beneficial to blood color; 4) occasional treatment of certain skin diseases; 5) promotion of mineral metabolism and formation of vitamin D in the body.
UV defects: 1) cause skin aging to produce wrinkles; 2) produce spots; 3) cause dermatitis; 4) cause skin cancer.
UVC UV knowledge
UVC sterilization principle:
Among the ultraviolet rays of various wavelengths, only short-wave ultraviolet UVC has the function of sterilization and disinfection. It belongs to pure physical disinfection method, and has the characteristics of broad spectrum, high efficiency, rapid and thorough, no need to add chemical agents, no drug resistance, no secondary pollution.
The UVD ultraviolet light with a wavelength of 185 nm can change the oxygen O2 in the air into the ozone O3. The ozone has a strong oxidation effect and can effectively kill the bacteria, but the ultraviolet light having a wavelength of 185 nm does not have a sterilization effect. The dispersion of ozone can just make up for the shortcomings that ultraviolet rays can only be transmitted in a straight line, and there is a dead angle in disinfection. It can reach any corner of the space with the air, so that sterilization and disinfection can be more thorough.
Principle of ultraviolet sterilization: The ultraviolet light illuminates microorganisms such as bacteria and viruses to destroy the molecular structure of DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) in the cells of microorganisms, causing DNA strand breaks and cross-linking of nucleic acids and proteins. Causes growth cell death and regenerative cell death, and achieves the effect of sterilization. Among them, the ultraviolet disinfection effect with the wavelength of 253.7nm is the best.
Principle of ozone sterilization: UVD ultraviolet light with a wavelength of 185 nm can oxidize air to decompose oxygen O2 molecules in the air, and the generated O atoms combine with O2 molecules to produce ozone O3. Ozone O3 has strong oxidation, can destroy the cell wall of decomposing bacteria, and penetrate into the cell to oxidatively decompose and destroy glucose oxidase, ribonucleic acid (RNA), deoxyribonucleic acid (DNA), protein, lipids, polysaccharides, macromolecular polymerization. The substance causes the bacteria's metabolism and reproduction process to be destroyed and dies, achieving the effect of sterilization.
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