This is a description of the Ionising Radiation analogy given by Claire Jones and Paul Henson of Brighton Hill Community College at the Surrey Physics Teach Meet on 2nd November 2011.
A pyramid of empty aluminium cans represents the electrons in an atom.
A football represents an alpha particle
A table-tennis ball represents a beta particle
An air-zooka or a hairdryer represents a gamma ray.
Get a pupil to throw the alpha particle at the cans, aiming to only knock the top one off. The will most likely knock them all down, showing how alpha is highly ionising. Get them to do the same with the ping-pong ball, and they’ll have more success in only knocking one can over, showing how beta is less ionising. Using the air-zooka or hairdryer from the same range will have no effect, showing how much less ionising gamma radiation is. You have to go close up for this to work.
Extension – penetrating power. Use a tennis net to represent paper, a net curtain to represent an aluminium sheet, and a sheet to represent a lead sheet. The ping-pong ball and air zooka will be able to penetrate the tennis net; only the air will penetrate the net curtain, and none of them will penetrate the sheet.