How Germicidal UV (UVC) Eradicates Germs

Germicidal ultraviolet (UVC) light kills cells by damaging their DNA. The light initiates a reaction between two molecules of thymine, one of the bases that make up DNA. UV light at this wavelength (shortwave UV or UVC) causes adjacent thymine molecules on DNA to dimerize. The resulting thymine dimer is very stable. If enough of these defects accumulate on a microorganism's DNA its replication is inhibited, thereby rendering it harmless.

Ultraviolet photons harm the  molecules of living organisms in different ways causing the distorted DNA

Ultraviolet photons harm the DNA molecules of living organisms in different ways. In one common damage event, adjacent bases bond with each other, instead of across the "ladder". This makes a bulge, and the distorted DNA molecule does not function properly.

The longer the exposure to UVC light, the more thymine dimers are formed in the DNA. If cellular processes are disrupted because of DNA damage, the cell cannot carry out its normal functions. If the damage is extensive and widespread, the cell will die.

The LIGHT SPECTRUM ranges from the infrared at wavelengths longer than visible light to the ultraviolet at wavelengths shorter than visible light. Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region.

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     Ultraviolet - wavelengths shorter than visible light. UVC, the germicidal UV, is also called shortwave UV.