Sunlight is an electromagnetic wave, divided into visible light and invisible light. Visible light refers to what the naked eye can see, such as the seven-color rainbow light of red, orange, yellow, green, blue, indigo, and violet in sunlight; invisible light refers to what cannot be seen by the naked eye, such as ultraviolet, infrared, etc. The sunlight we usually see with the naked eye is white. It has been confirmed that white sunlight is composed of seven colors of visible light and invisible ultraviolet rays, X-rays, α, β, γ, infrared rays, microwaves and broadcast waves. Each band of sunlight has different functions and physical properties. Now, dear readers, please follow the author to talk about ultraviolet light.

  According to different biological effects, ultraviolet rays are divided into four bands according to wavelength: long-wave UVA, medium-wave UVB, short-wave UVC, and vacuum wave UVD. The longer the wavelength, the stronger the penetrating ability.

  Long-wave UVA, with a wavelength of 320 to 400 nm, is also called long-wave dark spot effect ultraviolet light. It has strong penetrating power and can penetrate glass and even 9 feet of water; it exists all year round, no matter it is cloudy or sunny, day or night.

  More than 95% of the ultraviolet rays that our skin comes into contact with daily are UVA. 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. Therefore, UVA is also the wavelength that is most harmful to the skin.

  Everything has two sides. From another perspective, UVA has its positive effects. 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 tinted 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.

  Medium wave UVB, wavelength 275~320nm, also known as medium wave erythema effect ultraviolet light. Compared with UVA's penetration, it is considered moderate. 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.

  Like UVA, it will also oxidize the protective lipid layer of the epidermis, drying 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.

  However, people have discovered through scientific research that UVB is also useful. 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.

  Short-wave UVC, with a wavelength of 200~275nm, is also called short-wave sterilizing ultraviolet light. It has the weakest penetrating ability and cannot penetrate most transparent glass and plastics. Even a thin piece of paper can block it. The short-wave ultraviolet rays contained in sunlight are almost completely absorbed by the ozone layer before reaching the ground.

  Although UVC in nature is absorbed by the ozone layer before reaching the ground, its impact on the skin is negligible, but short-wave ultraviolet rays cannot directly irradiate the human body. If exposed directly, the skin will be burned in a short time, and long-term or high-intensity exposure may cause skin cancer.

  The effects of ultraviolet rays in the UVC band are very extensive. For example: UV 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.

  In summary, the advantages of ultraviolet light are: 1. Disinfection and sterilization; 2. Promote bone development; 3. Good for blood color; 4. Occasionally, it can treat certain skin diseases; 5. It can promote mineral metabolism and the formation of vitamin D in the body; 6. , promote plant growth, etc.

  The disadvantages of ultraviolet rays are: 1. Direct exposure will cause skin aging and wrinkles; 2. Skin spots; 3. Dermatitis; 4. Long-term and large amounts of direct exposure may cause skin cancer.

  How to avoid the harm of UVC ultraviolet rays to the human body? Since UVC ultraviolet rays have extremely weak penetration, they can be completely blocked by ordinary transparent glass, clothes, plastics, dust, etc. Therefore, by wearing glasses (if you don’t have glasses, avoid looking directly at the UV lamp) and covering your exposed skin with clothes as much as possible, you can protect your eyes and skin from UV

  It is worth mentioning that short-term exposure to ultraviolet rays is like being exposed to the scorching sun. It does no harm to the human body but is beneficial. UVB ultraviolet rays can promote mineral metabolism and the formation of vitamin D in the body.

  Finally, vacuum wave UVD has a wavelength of 100-200nm, which can only propagate in vacuum and has extremely weak penetration ability. It can oxidize oxygen in the air into ozone, called an ozone generation line, which does not exist in the natural environment where humans live.