In this activity, students use a free virtual Geiger counter from GigaPhysics.com to investigate the properties of alpha, beta, and gamma radiation, and then to identify an unknown source. The virtual Geiger counter lets students adjust the number and type of barriers (cardboard, lead, etc.) and even includes background radiation. In other words, we've replaced the room full of expensive Geiger counters, but we still work hard to retain the educational experience for your students.