Final answer:
UV light is an inefficient sterilizer because it requires multiple photons to damage organisms, cannot penetrate surfaces or packaging, and its effectiveness depends on intensity and exposure time. Despite these drawbacks, UV radiation is used in medical treatments and water purification, and it promotes vitamin D production.
Step-by-step explanation:
UV light is considered an inefficient mode of sterilization for several reasons. To begin with, UV radiation requires several photons to disrupt cell reproduction or kill bacteria, unlike y-ray or X-ray photons which can cause the same level of damage with a single photon. Moreover, UV light cannot penetrate surfaces or packaging materials like plastic or glass, limiting its sterilizing capability to only those areas that are directly exposed to the light source.
Another limitation is that UV light's efficacy in sterilization greatly depends on the intensity and exposure time. Low-intensity UV, while it can be used to sterilize surfaces and haircutting implements, does not deposit energy as efficiently as lower-frequency electromagnetic waves. It also does not ionize atoms and molecules as readily as higher-energy radiation such as X-rays or y-rays.
Despite these limitations, UV light is still employed in various applications including water purification, biological safety, and the treatment of medical conditions such as infantile jaundice. It is also beneficial in triggering the production of vitamin D in the skin, a process which visible light cannot accomplish due to insufficient energy levels.