These well meaning responses illustrate how difficult it is to address
scientific logic midst lack of basic knowledge and focus. A quick
answer to both serves not to 'rebut', ipso facto.
On Sunday, August 10, 2003, at 11:01 AM, John Hudson wrote:
I have the radioactive element from a 50/1.4 right in front of me (ok,
a couple of feet in front of me, and I'm not about to start carrying
it
in my pocket as a good-luck charm),
The above implies and leads others to believe that a person who carries
the 50/1.4 in their pocket will receive potentially harmful radiation
damage from such. First, as I have repeatedly asked, is there
definitive documentation regarding the exact radionuclide incorporated
in this lens? Once this is known, Nuclide charts can inform re the
percent of the nuclide in the element and the mode of decay with
emissions. If no penetrating photons are emitted by the decay, take it
to bed with you. Be factual. Determine exactly which element is
radioactive in the lens, then visit:
http://www2.bnl.gov/ton/
In a prior post, you deemed Thorium to be the culprit. Do you know for
a fact that Thorium was utilized in the making of Zuiko lens glass???
Thorium-232, the only naturally occurring nuclide of thorium, decays
solely by alpha emission. Given the long half-life, this will not keep
your pocket warm. Again, the decay of the daughter, Ra-228 is solely
by beta decay with no primary electromagnetic radiation to engender
biological risk. This daughter and several more generations decay by
either beta or alpha decay until stable Pb-208 is reached. The
multiple stages of decay with particulate emissions is NOT good for
glass, but of insignificant or no risk to people.
Rhetoric and speculation aside, what heavy or rare earth element was
added to the Zuiko glass? Once this is known, complete assessment of
the situation can be offered in a simple paragraph.
snip
How much more radioactive is this lens element than my thirty year old
wind
up Omega Speedmaster watch with luminous dial markings?
To enjoy and be informed of the answer, suggest you visit the library
for a book about the radium dial painters of the early 1900s. Because
of this tragedy, the use of radium in virtually all consumer products
from watches to 'snake oil' potions was prohibited by the 1950s. Alpha
and beta particles produce intense ionization tracks in tissue.
Ingested radium is deadly. The decay of radium and daughter nuclides
does produce some electromagnetic radiation, e.g. gamma rays, thus
biological radiation exposure, albeit small, can result from wearing a
'radium dial' watch.
When prohibited, the watch makers adopted two primary technologies.
Luminescent dials are created by phosphors which absorb light energy,
then release it in a slow manner. The other technology was to
incorporate
H-3, tritium, which is a pure beta emitter of 0.019 MeV max, a very low
energy. This was admixed with a phosphor which 'glowed' when energized
by the decaying tritium. The short 12.33 year half--life of tritium
'shortened' consumer acceptance when the dials began to dim.
There is no known radiation biology risk of wearing a 'tritium' wrist
watch. If you decided to ingest, indigestion would be a serious
complication, but not radiation risk.
Finally: "How much more radioactive......" is a major impediment to
understanding our naturally radioactive planet.
http://science.howstuffworks.com/nuclear1.htm has good introductory
material on types of radiation, modes of decay, etc. Enjoy your watch.
Bill Hunter
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