IOP Institute of Physics

# Teaching radioactivity: Summary and suggestions

Research has shown that many students misinterpret the scientific ideas about radiation and radioactivity and are unable to apply scientific ideas to help them understand real life situations where radiation and radioactivity are involved.

The main misunderstandings are:

• Many appear not to be able to clearly distinguish between ‘radiation’ and ‘radioactive substance’. This is also a common feature of lay understandings in general. For example, after the Chernobyl accident, many newspaper articles referred to a “cloud of radiation” and drinking water contaminated with “radiation”.
• Many students appear to interpret the idea that “radiation is absorbed” differently from the scientific interpretation. They believe that objects that have been irradiated will themselves become radioactive – that they can re-emit the radiation some time later. The underlying idea here is that they seem to think that radiation is somehow “conserved”. This is, of course, what we mean by ‘absorbed’ in everyday language. For example, when we say that a sponge has absorbed water, we assume that it can re-emit it at a later date.

These two areas of misunderstanding are, to some extent, related. They lead to:

• An inability to clearly differentiate between the ideas of irradiation and contamination
• An inability to satisfactorily interpret the ideas of activity and dose
• We also know that many students have difficulty making sense of explanation based on the particulate model of matter. This may pose a severe barrier to many students learning about radioactivity

The UYSEG scheme addresses these issues specifically by:

• Establishing a general model of radiation phenomena using the source, radiation, detector model. All radiation phenomena can be described in the same way:
Source -----radiation----- detector
• Dealing with the idea of absorption more directly and more fully than usual rather than assuming that students know what we mean by absorption of radiation.
• Spending time distinguishing between irradiation and contamination. In part, this is addressed through describing the source as a substance as distinct from a device (like a light bulb).
• Delaying the introduction of microscopic ideas until the end of the teaching sequence. This is quite radical. The aim of the UYSEG sequence is to engender a good understanding of the radiation and radioactivity at the macroscopic level before talking about particles.

The UYSEG sequence
This is a brief summary of the lessons in the UYSEG sequence, put into four groups.

Group 1. A phenomenological orientation.
Lesson 1. Source -> radiation -> detector model. Phenomena including light, infra-red and radioactivity can all be interpreted using this model.

Group 2. Qualitative macroscopic treatment.
Lesson 2. What happens when radiation is absorbed? Demonstrations using light show that the radiation can be absorbed and is no longer there. The absorber does not consequently become a light source.

Lesson 3. Three types of radiation. Experiments to show that there are three types of radiation from radioactive sources. These can be found in the Teachers TV programme.

Lesson 4. Radioactivity all around us. Introduces the idea that there are weak sources of radioactivity all around us - background radiation.

Lesson 5. Open and closed sources. The UYSEG scheme uses a simulation of the Chernobyl accident to distinguish between open and closed sources and the ideas of contamination and irradiation.

Lesson 6. Putting radioactive sources to use. For example as tracers and in medicine.

Group 3. A quantitative macroscopic treatment.
Lesson 7. Comparing sources. Activity and half life. The demonstrations and activities from the programme could be used here.

Lesson 8. Radiation dose. How much do we get? The background radiation worksheet could be used here.

Group 4. A treatment at the atomic level.
Lesson 9. Atoms, nuclei and transmutations. Only now are students introduced to an explanation at an atomic level. They consider the evidence for the explanations. The animations from the programme would be useful in this lesson.

Lesson 10. Randomness and chance. Simulations using dice and coins. The activities from the programme could be used here.