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Student Journeys for Understanding Radiation & Radioactivity Ryan Anderson, Anna Hafele (Andy Johnson) CAMSE, Black Hills State University, Spearfish SD 57799-9005 A project of the South Dakota Center for the Advancement of Math and Science Education http://www.camse.org/radiation The Inquiry into Radioactivity Project at Black Hills State University is supported by National Science Foundation grant DUE 0942699. Any opinions, findings, and conclusions or recommendations expressed in this poster are those of the authors and do not necessarily reflect the views of the National Science Foundation. Initial Ideas The IiR materials are being trial tested in a Survey of Physics course for non-science majors. Research data consisted of conceptual evaluations, homework, exam responses, etc. Not all data sets were complete. We examined all student work for evidence of undifferentiated thinking in three categories: • Radiation as “stuff”: Radiation can be ‘on’ or ‘in’ objects. • Contamination: Radiation makes other objects radioactive. • Radiation = radioactive: No distinction between the two. Figure 1 shows the percent of students for which we have data who showed evidence of fully differentiating radiation from radioactivity in all three categories - if it was possible to tell - at various points during the semester. Rounded boxes list significant content and concepts addressed by the course materials (usually worked out by students). Numbers next to data points are the numbers of students for whom codes could be assigned in that data set. Each student seemed to need different amounts of time to change their thinking about radiation and radioactivity. The differentiation process appears to be gradual, and to require extensive thinking about many related issues, often simultaneously. Roughly 80% of the students differentiated by the end of the semester. The remaining 20% appeared to be in transition but were reluctant to abandon their initial ideas. Undifferentiated students had greater difficulty understanding the ionizing process. Basics of radiation at macro scale Atoms as sources of radiation Interaction of radiation with life Recent renewed interest in nuclear power and the public response to the Fukushima disaster highlight the need for radiation literacy. The Inquiry into Radioactivity Project (IiR) is developing and testing course materials for non-science majors to understand basics of nuclear radiation and radioactivity. Students’ initial ideas strongly hamper their understanding radiation - they think of it as “bad stuff that makes other objects radioactive.” 1, 2, 3 Understanding the basics of radiation is essential to learning the ionizing process. 4 The IiR materials successfully move most students to conceptualize radiation as high speed subatomic particles. This is called the “differentiated view”. 1, 2 When does it happen? How difficult is this conceptual transformation? Other topic Detect background radiation everywhere Sporadic vs patterns vs causal Waves vs quanta vs stuff Counting and averaging Use St. Dev. to compare averages Randomness as chance events Discover natural & manmade radioactive sources Define “radioactive” Safety of classroom sources Elevation effects on background radiation EM vs light vs sound vs countable Test for contamination Test light salt for radioactivity Types via shielding - alpha, beta, gamma Strength vs penetrating power Source vs radiation Introduce “countable” name Identify types of radiation from natural sources Paths of radiation Radiation travels Waves vs quanta Electric charges & forces Basic atomic structure Protons attract electrons in orbits Size and scale of atoms Ions and p + e - balance Element name => proton # Naturally occurring isotopes vs non- natural Neutrons have no electrical effect Proton- neutron balance => stability Large nuclei emit 2p2n Neutron- rich emit electrons Emitted particles = radiation? Excess neutron converts to p + & e - Exploding nuclei transform to new elements Redefining radioactivity to include atoms Alpha = high speed He nuclei Beta = high speed electron from nuclei Gamma = energy packet Radiation quanta can remove atomic electrons Radiation quanta => no effect on nucleus Mechanisms of ionization by radiation particles Radiation quanta can break molecules Single beta ionizes many victim atoms Explaining tracks in cloud chamber Penetration range and scale of damage Alphas much more likely to interact with electrons Explain penetration power via likelihood of interaction Visualizing trails of damage in tissue DNA = main target for tissue damage Molecular mechanism for tissue damage Cell size & scale relative to radiation particles New name: Ionizing Radiation Stochastic vs. acute damage Small likelihood of cancer mutations Radiation dose considerations Chernobyl, Hiroshima, Fukushima Types of radiation treatments Curies, Litvinenko Environmental sources What average & St. Dev. mean N=34 N=30 N=34 N=32 N=17 N=25 N=21 N=27 N=23 N=34 N=34 “Another thing that kind of blew my mind was the orange plates that were so radioactive and when you took the apples off, they didn't appear to set off the geiger [counter]. I would have thought that it would transfer to the apple. . .” Fig. 1: Percent of students differentiating vs. time References: 1. Eijkelhof, H. M. C. (1990). Radiation and Risk in Physics Education. Utrecht, University of Utrecht. Web resource: http://www.iaea.org/inis/collection/ NCLCollectionStore/_Public/22/010/22010294.pdf Accessed March 30, 2012 2. Millar, R. and J. S. Gill (1996). "School students' understanding of processes involving radioactive substances and ionizing radiation." Physics Education 31(1): 27 - 33. 3. Prather, E. and R. Harrington (2001). "Student Understanding of Ionizing Radiation and Radioactivity: Recognizing the Differences Between Irradiation and Contamination." Journal of College Science Teaching 31(2): 89-93. 4. Hafele, A. and Johnson, A. (2012) "Exploring Learning Difficulties Associated with Understanding Ionizing By Radiation." NCUR 2012 Proceedings, Ogden Utah. Fig. 2: Example data of students initial thinking showing Stuff, Contamination, and Radiation = Radioactive • Nearly all students (88%) initially gave radiation stuff-like characteristics. An additional 11% appeared to have mixed ideas about stuff. • 65% of students said that radiation makes other objects radioactive and an additional 34% gave conflicting answers. • 94% of the students mentioned waves in their initial descriptions of radiation. • Most students did not differentiate between nuclear and electromagnetic radiation sources. Ideas in Transition a) Fumes above the drum imply stuff, as does “radiation on food”. b) The labels “radiation” imply no differentiation between “radioactive” and “radiation”. c) “Blew my mind” implies a belief that the apples should have been radioactive (contamination). a) b) c) Final Ideas Conclusions This example shows a nearly complete line of reasoning from an unstable 106 Ru nucleus to beta emission to the beta breaking molecules in a worker’s foot, to DNA damage. Many students developed this range of reasoning which is necessary for a full understanding of radiation’s origins, behavior, and effects on the body. Fig. 3. Early adaptation of thinking: Radiation becomes particles that are not moving Fig. 5: Student response to exam question “Describe the steps by which the foot is damaged by radiation.” Fig. 4: Partially differentiated thinking on contamination As students encountered new evidence they had to modify their initial ideas. However, their new ideas were often not yet fully consistent with accepted scientific ideas. The learning process involved students answering questions that mattered to them in ways that were increasingly consistent with all the evidence. Before the third cycle on radiation effects on living things, students were uncertain about how radiation can harm someone since it did not make them radioactive. Many hedged their statements, uncertain about their answer. Cycle 1 Cycle 2 Cycle 3
