Originally posted by Nesster the 55/1.8 or f/2 is not radioactive
Except for in the small study I linked to. Though in all fairness, the gamma count for that lens was much less than the ST 50/1.4.
Yes, gamma. Thorium decays by alpha emission with accompanying gamma radiation. What that means is that the atom spits out an alpha particle (essentially the same as a helium nucleus) and briefly "glows" with gamma waves. (Gamma is ionizing electromagnetic radiation with a wavelength somewhat shorter than x-ray.) Alpha particles are not particularly hazardous, while gamma may be.
The link I supplied above is interesting to me because the person who did it used a Geiger counter for initial screen (would count both alpha and gamma) followed a different setup using a gamma-specific scintillation detector.
Steve