Ultra Violet radiations come from Sun but cannot be seen by human naked eye and they have wavelengths beyond the wavelength of violet color of the visible spectrum of solar radiations. Ultra Violet radiations are divided in 3-regions as A, B and C. The ozone layer blocks the most dangerous UV rays in region-C and some wavelengths in region-B. UV rays in region-A cause skin browning while in region-B cause skin-burning. Wavelengths from 300-310 are the most dangerous and carcinogenic UV-radiations in region-B.
