Why is ultraviolet radiation dangerous?
We are all composed of molecules. The most famous is the DNA, which holds our genetic code. Molecules can be split by radiation, if the energy of the incident photons (see FAQ above) is sufficient. For many molecules, including the DNA, the critical threshold is in the UVB: The energy of photons in the UVA and visible is not sufficient to cause damage, however UVB photons will likely cause molecules to dissociate. Fortunately most damage can be repaired by our body. If, however, our immune system is weakened or we are exposed to high radiation levels (for example at the beach during noon) not all damage can be repaired. The consequences may be sunburn, snow blindness, or, in the worst case, skin cancer.
