3 ms·
> Since the decay chain of thorium consists exclusively of alpha and beta particle emission, neither of which is very penetrating, the closed shutter protects t
by SaberTail 7y ago
> Since the decay chain of thorium consists exclusively of alpha and beta particle emission, neither of which is very penetrating, the closed shutter protects the film from the radiation from the rear of the lens.
This isn't true. Thallium 208, for example, is on the decay chain. Yeah, it beta decays to lead, but it also emits a 2.6 MeV gamma ray in the process [1]. That's one of the highest energy gamma rays you typically see from radioactive decay, and it's highly penetrating. That's one example, and there's also lead 212 and actinium 228, which also peaks in the 100s of keVs.
[1] See the "gammas" part of http://nucleardata.nuclear.lu.se/toi/nuclide.asp?iZA=810208 http://nucleardata.nuclear.lu.se/toi/nuclide.asp?iZA=810208
- alecmg 7y agoAm I reading it wrong? Tl208 to Pb is beta decay, there are no gamma particles involved. I would think the 2.6 MeV energy listed is for the electron emitted.
- SaberTail 7y agoYou're not reading it completely wrong. There is a beta decay. Look at the last page of this table: http://www.nucleide.org/DDEP_WG/Nuclides/Tl-208_tables.pdf http://www.nucleide.org/DDEP_WG/Nuclides/Tl-208_tables.pdf The green arrows are possible beta decays to lead 208. But 208Tl never decays to the nuclear ground state of lead 208. And so after the beta decay, there are gamma rays (the black arrows) as the nucleus relaxes from whatever excited state it ended up in.