Sunlight has been known for years to have a bactericidal effect; nut the effect is due primarily to ultraviolet rays in the sunlight.
Strong visible light, which contains light of wavelength from 400 to 700 nm (violet to red light).
Mode of Action:
Visible light can have direct bactericidal effects by oxidizing light-sensitive molecules such as riboflavin and porphyrins (components of oxidative enzymes) in bacteria. For that reason, bacterial cultures should be exposed to strong light during laboratory manipulations.
Application of Strong Light:
The fluorescent dyes cosin and methylene blue can denature proteins in the presence of strong light because they absorb energy and cause oxidation of proteins and nucleic acids. The combination of a dye and strong light can used to rid materials of both with bacteria and viruses.
Radiation Spectra is available here.