1.Previous
3.Next

absorbs some 98% of non-ionizing but dangerous UV-C and UV-B. This ozone layer starts at about 20 miles and extends upward. Some of the ultraviolet spectrum that does reach the ground is non-ionizing, but is still biologically hazardous due to the ability of single photons of this energy to cause electronic excitation in biological molecules, and thus damage them by means of unwanted reactions. An example is the formation of pyrimidine dimers in DNA, which begins at

1.Previous
3.Next