ABSTRACT
Even though there is a continuum of energies in the electromagnetic spectrum of radiations, the ultraviolet (UV) has been divided into UVC (below 290 nm, nonsolar), UVB (290-315 nm), and UVA (315-400 nm) for categorizing the main e¨ects of solar exposure on human skin. Wavelengths below 290 nm are blocked by the stratospheric ozone. §ese wavelengths are of the highest energies (>4.4 eV) and coincide with maximal absorption by DNA and other biomolecules, and would be extremely damaging to genetic material and biological tissues in general if they reached the surface of the earth. §e stratospheric ozone layer therefore protects life from UVC radiation, also called abiotic radiation.
