UVGI is most effective on microorganisms within which range of the light spectrum?

UVGI, or Ultraviolet Germicidal Irradiation, is a disinfection method that utilizes short-wavelength ultraviolet light to kill or inactivate microorganisms. The effectiveness of UVGI is predominantly found in the range of 200 to 280 nanometers, which corresponds to the UV-C spectrum. This range is particularly effective because it is where the UV light is absorbed most effectively by the nucleic acids in microorganisms, leading to the formation of dimers in the DNA and ultimately resulting in the disruption of their cellular function.

At the lower end of the spectrum, around 200 nanometers, UV light has a high germicidal effectiveness, while light above 280 nanometers, particularly into the UV-B and UV-A ranges, has significantly less impact on microbial inactivation. Thus, the choice that identifies the range of 200 to 280 nanometers aligns with the scientifically established understanding of UVGI effectiveness, making it the correct answer.