If I shone a UVC lamp (11W) on something (say for example a plastic phone case) for an hour, would that kill off a noticeable amount of bacteria? That is, if I were to go over the case with a cotton swab before the hour and swipe the cotton swab over a petri dish with nutrients and if I were to do the same after the hour with a different cotton swab and a different petri dish. Do you think that after a week there would be a noticeable difference in bacterial growth between the dishes? I think it should, since some filters for ponds work the same way, but I'm not sure, since in my case, the light needs to penetrate about 10 inches of air first and the environment isn't as closed off. What are your ideas on this?

  • $\begingroup$ I think you should add distance parameter to it because it has inverse relation with any rays that use for such uses $\endgroup$ – M007 Oct 9 '14 at 17:41

Some physical methods of sterilisation are in hospitals

  • Steam autoclaving
  • Dry heat – thermostat
  • White light / UV light sterilization

where continuous UV light has poor penetration. UV radiation heat is absorbed by proteins and nucleic acid. All micro-organisms contain tehm. They inactivate the DNA. There will be electronic and photochemical reactions by

  • photolysis
  • loss of colony-forming ability
  • enzyme inactivation
  • destruction of nucleic acid.

If I shone a UVC lamp (11W) on something (say for example a plastic phone case) for an hour, would that kill off a noticeable amount of bacteria?

Direct answer: Not all bacteria, but some. UV light has poor penetration so it will not expose all bacteria. Most prevalent bacteria there

  • streptococci,
  • staphylococci and
  • some others.

I estimate that the majority of the bacteria will remain because the light cannot reach each corner of the object. In clinics, many hours and high temperatures are used to kill bacteria. UV light is not efficient there. I think the problem is that you cannot reach each corner of the object. The high temperature and disinfectants can then again reach the clinical instruments throughly. Manual work is however still needed.

You can then take examples of bacteria. Search their corresponding temperature ranges. The survival can also be dependent on the nature of the light of the bulb. Each bacteria has an individual structure. We can manipulate the environment to make bacteria more vulnerable to the heating i.e. to change the structure of the bacteria. We can increase the duration of the heat exposure to make kill of the bacteria more effective.

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