Ultraviolet rays and uv meter

When ultraviolet rays are irradiated, the degree of eye injury is proportional to the time, inversely proportional to the square of the distance from the source, and related to the projection angle of the light. Regarding the harm of ultraviolet rays to human health:
When ultraviolet rays act strongly on the skin, photodermatitis can occur, and erythema, itching, blisters, edema, eye pain, tearing, etc. appear on the skin; severe cases can also cause skin cancer.
Ultraviolet rays act on the central nervous system, causing headaches, dizziness, and increased body temperature. Acting on the eyes, it can cause conjunctivitis, keratitis, called photoophthalmia, and may also induce cataracts. The ultraviolet rays generated during the welding process can cause welders to suffer from electro-optic ophthalmia (can be cured). UV meter can be used to test the uv irradiation intensity of the light sources.
Although ultraviolet rays exist throughout the year, the winter sunlight is relatively mild and the north is foggy, but the ultraviolet rays are only about 20% weaker than summer, and they still cause great harm to human skin and eyes. Therefore, it is still necessary to avoid ultraviolet rays in winter. Irradiation. Long-term ultraviolet radiation is most likely to cause various spots on the skin. Therefore, even in the cold winter, you should apply barrier cream or sunscreen during outdoor activities. Of course, an SPF index of 15 is enough. If you are going out for skiing or staying in the snow for a long time, it is best to wear goggles to prevent ultraviolet rays and strong white light from the snow from irritating your eyes.
In recent years, a large number of chemicals have destroyed the ozone layer in the atmosphere and destroyed this natural barrier that protects human health. According to a report provided by the National Meteorological Center, China's total atmospheric ozone layer has decreased year by year since 1979, and the ozone layer has decreased by 14% in 20 years. And for every 1% decrease in the ozone layer, the incidence of skin cancer will rise by 3%. At present, the Beijing Municipal Meteorological Bureau has issued the Beijing UV Index to help people properly prevent UV radiation.