One thing is not clear to me. When alpha or beta or gamma radiation enter into geiger counter, it ionizes the gas and ionization current produces counts in the detector. What exactly this counts indicate? Does it show the number of alpha or beta particles enter into the tube? Since even if one mill gram of a sample will contain millions of atoms, at any instant what will be the probability of number of atoms that decay by emitting alpha or beta particles? What is the mechanism of counting the number of alpha or beta particles by the counter? Also in the case of gamma rays, how is the count done, since they are only electromagnetic waves but not particles? Can any body explain?