Hi there, I have a few closed radioactive sources (Cs137, Pb210, Na22) that I am trying to use for a project but I am not that knowledgeable about them. Their activity is shown on the source but I'm unsure if this is related to the amount ie grams of substance inside the sealed container, or if it relates to how much radiation is actually being emitted from the sealed container. ie. internal absorbtion is accounted for. For beta radiation in particular I would think that a large portion would be re-absorbed by the plastic mold it is kept in. I am trying to find the beta efficiency and gamma efficiency of some geiger tubes and am wondering if it is even possible with what I have?? Thanks!