Are alpha particles more ionising than beta?
Teaching Guidance
for 14-16
Do alpha particles cause more ionisations of the air than beta particles?
Wrong Track: Alpha radiation is more ionising than beta radiation.
Right Lines: If both alpha and beta particles start with the same energy, then they will each undergo the same number of ionising collisions, shifting the same amount of energy per collision with air molecules before coming to a stop.
Rate of ionisation and total ionisation
Thinking about the learning
It is quite common to see statements along the lines of alpha particles are more ionising than beta
, but this is not actually the case if both kinds of particle start with the same energy.
Thinking about the teaching
The point to stress here is that the alpha radiation causes ionisation over a shorter path, creating a higher density of ionising collisions than beta radiation.
