Final answer:
UV-C radiation kills bacteria by damaging DNA, and X-rays do so by penetrating cells and causing DNA and cellular damage. Both are used in various settings for disinfection but require careful handling because of their potential to harm living tissues.
Step-by-step explanation:
The wavelengths of radiation that are effective at killing bacteria and the methods by which they do so are:
- UV-C: This type of ultraviolet radiation can damage DNA by causing thymine dimers to form within a DNA strand, leading to mutations and eventually, cell death. Devices that emit UV-C light, such as germicidal lamps, are used in a variety of settings to disinfect water and surfaces.
- X-rays: With shorter wavelengths than UV light, X-rays are a form of ionizing radiation that can penetrate cells and cause damage to DNA and other cellular components. This damage can result in mutations, cell death, or cancerous growths.
- Infrared and microwaves are not typically recognized for killing bacteria through the mechanisms mentioned in the student's choices (B and D), and therefore were not included in this explanation.
While UV radiation and X-rays are effective at controlling microbial growth, they must be used with caution due to their potential to harm living tissues.