(a(i))[1]
State the meaning of random decay.
(a(ii))[2]
State the meaning of decay constant.
(b)[5]
The radon gas activity in a sample of air from a building, taken from $4.80 \times 10^{-3}\,\text{m}^3$ of air, is $0.600\,\text{Bq}$. A volume of $1.00\,\text{m}^3$ of air contains $2.52 \times 10^{25}$ air molecules. Calculate, for $1.00\,\text{m}^3$ of the air, the ratio $$\frac{\text{number of air molecules}}{\text{number of radon atoms}}.$$