ABSTRACT
Ultraviolet (UV) rays are invisible electromagnetic waves with a wavelength of 100-400 nm, classied as vacuum UV (100-190 nm), UVC (190-290 nm), UVB (290-320 nm), and UVA (320-400 nm) based on their biologic activity. Vacuum UV and UVC do not reach the surface of the earth, whereas approximately half of all UVB and almost all UVA rays reach the earth’s surface. UV (UVB + UVA) energy comprises only a small amount of the total energy of the sun’s rays. Nevertheless, UV rays cause crucial damage with quite high energy to living organisms, and various defense systems have evolved in these organisms for protection.
