Student Understanding of Half-life and Background Radiation

Abstract

We have been studying the conceptual understanding of high school students about radioactivity, particularly regarding background radiation and half-life. We have seen that it is difficult for learners to grapple with the idea that random behavior of individual atoms can give rise to predictable patterns in the collective, and many students have said both on the Stochastic World of Radioac-tive Decay Evaluation (SWORDE) and in interviews that, if you are looking at an individual atom, half of the atom will have fissioned after one half-life. Our findings have indicated, however, that this idea (of individual atoms fissioning in a predictably continuous manner) is often not a robust and intact mental structure; rather, in other contexts, the same students correctly discuss fission as being instantaneous and unpredictable. Approaches to teaching radioactivity that take this fluidity of student reasoning into account are desired. We created and validated an expanded version of SWORDE and are using the survey to assess "The Radiation Around Us", curriculum that does exactly that.