Ultraviolet radiation (UVR) is one of the most
important environmental factors influencing the
human body. Discovered in the early nineteenth
century by Johann Wilhelm Ritter, ultraviolet
electromagnetic radiation is invisible to the human
eye, with a wavelength shorter than visible
light (390-700 nm) and longer than x-rays (0.01-
10 nm). Due to the different biological effects of
UVR, there is a division into three main areas: