A group of students uses 4000 custom octagonal (8-sided) spinner discs to model the decay of a radioactive material. Each spinner represents a single undecayed nucleus. A spin of all remaining discs represents a constant time interval.
When the spinners are spun, any disc that lands on the number 1 represents a decayed nucleus and is removed. The students count the number NNN of 'undecayed' spinners that remain. The procedure is repeated using the remaining undecayed spinners.
The figure below shows the students' data.
Explain why NNN has been plotted on a logarithmic scale.
In this simulation, a decay constant λ\lambdaλ can be defined that models the radioactive decay constant. Determine λ\lambdaλ in spin−1\text{spin}^{-1}spin−1. Go on to use your value for λ\lambdaλ to show that n=8n = 8n=8 for the spinners used in this experiment.
A typical radioactive source used in high-school demonstrations has an activity of 100 kBq100\text{ kBq}100 kBq. An industrial radiography source used to inspect structural welds has an activity of 4.5 TBq4.5\text{ TBq}4.5 TBq. State one safety precaution when using the source in a school laboratory, and explain how this safety measure must be adapted for safe use of the industrial radiography source.
