Does penetrating power alone indicate danger?
Teaching Guidance
for 14-16
Is gamma more dangerous because it has greater penetrating power?
Wrong Track: There are three types of radiation. Gamma is the most dangerous because it can even go through a sheet of lead. Alpha can be stopped by a sheet of paper so it is least dangerous.
Right Lines: The danger of a source to human tissue is not necessarily linked directly to its penetrating power.
You can't tell how dangerous a source is just from the penetrating power
Thinking about the learning
Students often assume that gamma radiation is more dangerous than alpha and beta because it has a greater penetrating power.
Thinking about the teaching
Students tend spontaneously to associate the greatest penetrating power with the greatest danger, but in fact alpha radiation, which has the smallest penetrating power, can in some cases be the most dangerous. For example, if the alpha-emitting radioactive material is taken into the body through the mouth or lungs, highly-ionising alpha radiation is emitted directly into human tissue with critical consequences.
