Ultraviolet rays can be divided into four bands according to wavelength:
Long wave UVA, medium wave UVB, short wave UVC, vacuum wave UVD.
The longer the wavelength, the stronger the penetrating ability.
1) First let's talk about UVA
UVA, with a wavelength between 320 and 400 nanometers, has strong penetrating power and can penetrate glass and even 9 feet of water; it exists all year round, whether it is cloudy or sunny, day or night.
Degree of damage to the human body: More than 95% of the ultraviolet rays that the skin comes into contact with daily are UVA, so it is the most harmful to the skin. UVA can penetrate the epidermis and attack the dermis, causing severe damage to the collagen and elastin in the skin. Moreover, dermal cells have poor self-protection ability, so a very small amount of UVA can cause great damage. Over time, problems such as skin sagging, wrinkles, and the emergence of capillaries occur. At the same time, it can activate tyrosinase, leading to immediate melanin deposition and new melanin formation, making the skin darker and lack luster.
UVA can cause long-term, chronic and lasting damage and premature aging of the skin, so it is also called aging rays.
Application fields: UVA ultraviolet rays with a wavelength of 360nm conform to the phototaxis response curve of insects and can be used to make insect traps. UVA ultraviolet rays with a wavelength of 300-420nm can pass through special colored glass lamps that completely cut off visible light, and only radiate near-ultraviolet light centered at 365nm. It can be used in ore identification, stage decoration, banknote inspection and other places.
2) UVB
Medium wave UVB, the wavelength is between 275 and 320 nanometers. Medium penetration, its shorter wavelength will be absorbed by transparent glass. Most of the medium-wave ultraviolet light contained in sunlight is absorbed by the ozone layer. Only less than 2% can reach the earth's surface. It will be particularly strong in summer and afternoon.
Degree of damage to the human body: It will oxidize the protective lipid layer of the epidermis and dry out the skin; further, it will denature the nucleic acids and proteins in the epidermal cells, causing symptoms such as acute dermatitis (i.e., sunburn), and the skin will turn red. , pain. In severe cases, such as prolonged exposure to the sun, it can easily lead to skin cancer. In addition, long-term damage from UVB can also cause mutations in melanocytes, causing sun spots that are difficult to eliminate.
Application fields: Ultraviolet health care lamps and plant growth lamps are made of special transparent purple glass (which does not transmit light below 254nm) and phosphors with a peak value near 300nm.
3) UVC
Short-wave UVC, with a wavelength between 200 and 275 nanometers, is also called short-wave sterilizing ultraviolet light. It has the weakest penetrating ability and cannot penetrate most transparent glass and plastics. The short-wave ultraviolet rays contained in sunlight are almost completely absorbed by the ozone layer before reaching the ground.
Degree of damage to the human body: UVC in nature is absorbed by the ozone layer before it reaches the ground, and its impact on the skin can be ignored. However, in fact, short-wave ultraviolet rays are very harmful to the human body and cannot be directly irradiated to the human body. If exposed directly, short-term exposure can burn the skin, and long-term or high-intensity exposure can also cause skin cancer.
Application fields: Ultraviolet germicidal lamps emit UVC short-wave ultraviolet rays. Short-wave UV is widely used in hospitals, air conditioning systems, disinfection cabinets, water treatment equipment, drinking fountains, sewage treatment plants, swimming pools, food and beverage processing and packaging equipment, food factories, cosmetics factories, dairy factories, breweries, beverage factories, Areas such as bakeries and cold storage rooms.
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