Purple light is also called UV light. Purple light is the light with the shortest wavelength among visible light. Purple light in some wavebands is often called “black light” because the light in these wavebands is invisible to the human eye. UV violet light is an electromagnetic wave with shorter wavelength than visible light and longer wavelength than X-ray. From the perspective of the impact on human health and environment, UV violet light can be divided into the following levels according to wavelength:
UV violet light: visible violet light (400-420nm)
UVA (315~400nm), also known as long wave violet light or “black light”.
UVB (280~315 nm), also known as medium wave violet light.
UVC (200~280nm), also known as short wave violet light or bactericidal violet light.
UVD: vacuum ultraviolet ray (100-200nm)
The sunlight contains UVA, UVB and UVC ultraviolet light. However, due to the absorption of the ozone layer in the air, 99% of the ultraviolet light reaching the ground is in the UVA band.