One summer during high school I worked in a supermarket. On one occasion I was sent over to the floral department to do something, and there was someone with a geiger counter. Another employee pointed out to me that the geiger counter clicked like crazy when it was put near a certain spot. This spot was somewhere along where the overhead lighting was above the plants. I didn’t find out what could be the cause, and I am still curious. First, why would someone think to bring a geiger counter to a floral dept. and second, what could be the source of the apparent radiation?
Overhead lighting, like most all electronic devices, will emit at least a small amount of radiation when being used. If it were a sun lamp, then I’d imagine that slightly more than the usual amounts of radiation would be emitted, it being artificial sunlight.
But I couldn’t imagine that the Geiger counter would “click like crazy” by that thing unless it was somewhere very close to the source. Radiation like that doesn’t travel far (unless you’ve got a chunk of uranium on hand, in that case WATCH OUT). It also depends on what sort of radiation we’re dealing with. Alpha radiation can be blocked with a sheet of paper, it being a wave of basically hydrogen protons (I wonder if you could feel that). I’d imagine the counter would be picking of beta particles (electrons). If it was detecting gamma radiaton, then this would be something.
Why didn’t you ask the guy what he was doing?
Might be a fire/smoke detector. I suppose it’s wildly possible that the acoustic tiles in the ceiling might have a mineral component that was mildly radioactive. But your most likely culprit is the ballast in the fluorescent light. I did a Google search on radioactivity and lighting and found the following:
" Fluorescent Lamp Disposal
All fluorescent lights contain small amounts of mercury, and some compact fluorescent lamps with magnetic ballasts contain small amounts of short-lived radioactive material."
in a fact sheet from the Department of Energy.
Now why someone would be wandering around with a geiger counter in a supermarket escapes me.
If you re-read that excerpt from DoE fact sheet again, it doesn’t really say the ballast contains the isotope. The lamp or tube (which needs a magentic ballast) does. I use a compact fluorescent on which I can switch tubes and keep the same ballast. One the side of the tube’s package says “Each lamp uses a glow switch containing less than 15nCi of KR-85.” Krypton 85 has a half-life of 10.74 years.