Would the grain show up in digital pictures as well or only on film? I know why it appears on film but the gnomes that work my cell phone camera won't give me a straight answer.
I’m not even sure it would show up on film either. But for CCD cameras (aka phone cameras and basically all modern cameras), 350 americium buttons buttons from a smoke detector in a wide “stew” that far away would produce nowhere near enough ionizing radiation to do that. On top of it, americium-241 is an alpha emitter, meaning that even if alpha particles reached the lens, the lens itself would block a good amount an alpha. This video gives a demo of a CCD without protection over it with americium and other various emitters :)
Pretty much, but highly dependent on the energy of the ionizing radiation. Lower would come out as a dull grain, higher would show up as bright spots. Neither would look like this post though lol