Many students are unable to distinguish between non-ionising and ionising radiation and many do not think of light as ‘radiation’
Misconception
Resources to Address This
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A suggestion for linking the energy delivered by photons to frequency based on the ‘orange liquid’ approach to energy stores. Different sized spoons deliver different volumes of the fluid and therefore different amount of energy.
Discuss this in terms of how the increase in energy could affect a material, particularly the energy needed to release electrons from atoms or molecules, rather than a gain in the thermal stores of the material.
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Here, a more formal approach is taken to discussing the relationship between energy and frequency of radiation through the Planck equation E = h × f. Use the resource to discuss how high frequency electromagnetic radiation such as ultraviolet, X-rays and gamma radiation, causes ionisation when the energy is gained by electrons allowing them to escape atoms.
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A discussion of how frequency and energy delivered by photons is related. Use this to help explain why low frequency (low energy) photons are unable to cause ionisation effects, although they can still cause significant heating.
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A set of diagnostic question and answers can be useful to assess students understanding of ionisation. The questions can be useful in discussing how radiation can affect objects, leading to potential damage through ionisation but not contamination.
Students should also discuss absorption of non-ionising radiation and how this can affect materials.
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References
- Rego, F. and Peralta, L., () Portuguese students’ knowledge of radiation physics, Physics Education, 41, 259,