Excursion – Radioactive Lenses

8 thoughts on “Excursion – Radioactive Lenses”

  1. Ok just to keep you informed. Although Thorium does emit mostly alpha particles remember that the decay chain of thorium turns it into much more radioactive elements such as radium and radon which do emit beta and gamma radiation. So some 40 years after it was made you may find it a little more radioactive. Still nothing to really be worried about and moving even half a meter away would probably lower the cpm to background levels. However I wouldn’t feel too comfortable if it shattered and filled the air with Thorium dust as the small amount that would remain after passing through the body would go to the skeleton and be there for life. Also wouldn’t use it for baby pictures as they are much more sensitive to radiation given their cells have many more future divisions to go through compared to an adult.

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    1. The half life of Thorium is so exorbitantly high that I highly doubt you’d measure any difference in radiation after a hundred years. Sure, I primarily detect beta radiation from decay products of Thorium, alpha particles wouldn’t make it through the outer glass elements
      Gamma radiation is not really present, the GM counter doesn’t register anything outside my canvas camera bag.

      But I do agree, destroying the lens – even taking it apart – is a very unhealthy procedure. The thoriated glass sits on the inside, shielded by metal and glass.
      I’d say that radiation levels would be ten times higher if not more were the glass on the outside. (look at how much a lens cap can absorb..)

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  2. Calcium fuoride is actually a low index of refraction material with very low dispersion. Thorium dioxide has very index of refraction (highest of all known oxides) and quite low dispersion. Very different animals.

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