Explain the mechanism of action of ultraviolet radiation on cells

It gets absorbed into the cells and causes thymine dimers to form in nucleic acid. Ultraviolet radiation can mediate damage through two different mechanisms. One is through direct absorption of the incident light by the cellular components resulting to exited state formation and subsequent chemical reaction. The second one is photosensitization mechanisms where light is absorbed by endogenous (exogenous) sensitizers that are excited to their triplet states.