Normal yearly background dose, ~4000 uSv. Yearly dose from naturally occurring Potassium in the body is 390 uSv.
If you are worried about a old lens being in the same room as yourself, you should not be eating banana's, taking flights, or even live in a concrete/stone/brick house.įlight from LA to New York is 40 uSv. The fact that a lens can affect film is to do with the fact that film is a very sensitive detector of radiation, and that a lot of thoriated lenses had the thorium in the rear element, so the radiation would be highest inside the camera. From what I've read, the '1 x-ray equivalent per hour exposure on direct contact' is roughly the figure out there - something like the extra radiation you'd get crossing the USA in a jet.
#Pentax forum de how to#
Getting a detector would be interesting, but how to interpret the result is something I wouldn't be able to comment on (I do have a degree in physics, and I've worked in a nuclear lab, but these things are complicated and I'm no expert). Personally, it's not something I worry about, but I can sympathize with those who feel uneasy. As the half-life of thorium is millions of times longer than the daughter elements, I would expect the count from beta to be approximately equal to the counts from alpha, which is pretty much the impression I get from his impromptu experiment in the video (about half the intensity of radiation detected when the lens is under the table). As to the radiation, I was wrong to say the thorium glass only emits alpha particles - the thorium does only emit alphas, but the decay product (radon 228) is a beta emitter, as is its daughter, actinium 228. I don't know what the lens is that he's discussing - it looks like a Kodak Aero Ektar (anybody?) and they did have a reputation for being hot in their day. Not all Fuji fanboys are sane! However, that doesn't mean I think everything he says is nonsense Unfortunately, the person in the video is a believer in pseudo science and a conspiracy theory fan (I quote "light is not a particle, anyone who tells you that has been sucking on the cancer-stick of quantum theory").
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