Block UV Rays As Long As It Is UV400
Ultraviolet light is a general term for radiation from 10 nm to 400 nm in the electromagnetic spectrum, which is invisible to the human eye. Ultraviolet rays can be classified into short-wave ultraviolet rays (UVC, 100 to 280 nm), medium-wave ultraviolet rays (UVB, 280 to 315 nm), and long-wave ultraviolet rays (UVA, 315 to 400 nm). The main ultraviolet light source in nature is the sun. When the sunlight passes through the atmosphere, the ultraviolet light with a wavelength shorter than 290 nm is absorbed by the ozone layer in the atmosphere. Therefore, all UVC and most of the UVB are absorbed by the ozone layer. The main impact on the human body is UVA and some UVB.