According to the different biological effects, UV is divided into four bands according to the wavelength: long-wave UVA, medium-wave UVB, short-wave UVC and vacuum wave UVD. The longer the wavelength, the stronger the penetration.

UVA.
The wavelength of long-wave UVA, is between 320nm and 400nm, which is also called long-wave black spot effect ultraviolet. It has a strong penetrating power, can penetrate glass, even 9 feet of water, and exists throughout the year, sunny or cloudy, day and night.
The degree of harm to the human body: more than 95% of the ultraviolet rays exposed to the daily skin is UVA, so it is the most harmful to the skin. UVA can attack the dermis through the epidermis, causing severe damage to bone collagen and elastin in the skin; and dermal cells have poor self-protection, a very small amount of UVA can cause great damage. Over time, the skin produces problems such as relaxation, wrinkles and the emergence of microvessels.
At the same time, it can activate tyrosinase, resulting in immediate melanin deposition and new melanin formation, making the skin blackened and lack of luster. UVA can cause long-term, chronic and lasting damage, making the skin aging prematurely, so it is also known as aging rays.
Application: UVA ultraviolet at 360nm wavelength accords with the phototaxis response curve of insects and can be used to make insect trapping lamps. The UVA ultraviolet at 300-420nm wavelength can pass through the special colored glass lamp with completely off visible light, and only emit near ultraviolet light with 365nm as the center, so it can be used in ore identification, stage decoration, banknote inspection and other places.

UVB.
The wavelength of medium wave UVB, is between 275nm and 320nm, also known as medium wave erythema effect ultraviolet. Medium penetration, its shorter wavelength will be absorbed by transparent glass, ultraviolet B in sunlight is mostly absorbed by the ozone layer, only less than 2% can reach the earth's surface, will be particularly strong in summer and afternoon.
Degree of injury to the human body: it will oxidize the protective lipid layer of the epidermis and dry the skin; further, it will denature the nucleic acid and protein in the epidermal cells, resulting in symptoms such as acute dermatitis (that is, sunburn), and the skin will turn red and painful. In severe cases, such as prolonged exposure to the sun, it is also easy to cause skin cancer. In addition, the long-term damage of UVB will also cause melanocyte mutation, resulting in difficult to eliminate solar spots.
Application: ultraviolet health lamp and plant growth lamp are made of special transparent purple glass (not passing through the light below 254nm) and phosphors with peak value near 300nm.

UVC.
The wavelength of shortwave UVC, is between 20000nm and 275nm, also known as shortwave sterilized ultraviolet. It has the weakest penetration ability and cannot penetrate most of the transparent glass and plastic. The shortwave ultraviolet rays contained in sunlight are almost completely absorbed by the ozone layer and are absorbed by the ozone layer before reaching the ground.
Degree of damage to the human body: the UVC in nature is absorbed by the ozone layer before it reaches the ground, so the impact on the skin can be ignored, but in fact, short-wave ultraviolet radiation is very harmful to the human body and can not directly illuminate the human body. If direct exposure, short-term exposure can burn the skin, long-term or high-intensity irradiation will also cause skin cancer.
Application: ultraviolet germicidal lamp emits UVC short-wave ultraviolet. 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, bakeries and cold rooms.