UVB: Ultraviolet (UV) light is an electromagnetic radiation with a wavelength from 400 nm to 100 nm, shorter than that of visible light. Though usually invisible, under some conditions children and young adults can see ultraviolet light.
Overexposure to UVB radiation not only can cause sunburn but also some forms of skin cancer. However, the degree of redness and eye irritation do not predict the long-term effects of UV, although they do mirror the direct damage of DNA by ultraviolet.
The World Health Organization (WHO) classifies broad-spectrum ultraviolet radiation as a Group 1 carcinogen.
Ultraviolet light is also responsible for the formation of bone-strengthening vitamin D in humans. The UV spectrum thus has effects both beneficial and harmful to human health.