Exploring Learning Difficulties Associated with Understanding Ionizing By Radiation

Anna Hafele


What does the word "ionizing" mean in the phrase "ionizing radiation"? This question serves as a litmus test for student understanding on how radiation affects matter. The focus of this investigation is how non-science undergraduates can come to understand the interaction of radiation with matter through inquiry. The above question helps classroom researchers determine whether students have a coherent mental model of the ionization process, in which high speed subatomic particles (radiation) knock electrons out of atoms rendering them ionized. Substantial pedagogical support is required to get more than a small fraction of the class to develop usable models of ionization. Despite carefully planned instruction on ionization only 12% of non-science majors answered this question correctly the first time it was asked two years ago. In response to this problem extensive support was developed including research-based strategies and a new simulator for ionization by radiation. Although much progress has been made in the number of students who understand the ionization process, approximately 30% of the students still fail to understand this fundamental radiation process. Understanding ionization requires understanding three things: what an ion is, the basic characteristics of radiation, and the process of ionization. Students then must put these ideas together to create a complete mental model of the ionization process. The goals of this study are to identify the learning difficulties and their possible causes, exploring possible ways to resolve them. Mixed methods were used to infer students thinking using data from video, exams, journals, interviews, and homework. This research is part of the Radiation By Inquiry project supported by NSF DUE grant 0942699.


Physics Education; Inquiry; Ionizing

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