The purpose of a radioactivity based lab experiment is to measure the strength and shielding of different forms of radiation.  A Geiger counter is used to measure radiation strength around a radioactive object.  Different types of shielding are then placed between the radioactive object and the Geiger counter.  If the radiation is effectively shielded, the Geiger counter will cease to make noise.  If the radiation is not effectively shielded, the Geiger counter will continue to make noise.  Certain radioactive objects can be effectively shielded by simple shielding like paper or water.  Other sources of radiation (like x-rays) require more serious shielding like a lead apron.