Coastal engineers use a radioactive tracer to follow the movement of silt at sea.
The tracer has a half-life of 5 hours5\ \text{hours}5 hours and the final measurement is taken 15 hours15\ \text{hours}15 hours after the tracer is prepared.
The tracer must meet both conditions shown in the table.
| Time | Condition |
|---|---|
| At the final measurement | activity is at least 0.20 MBq0.20\ \text{MBq}0.20 MBq |
| 20 hours20\ \text{hours}20 hours after the final measurement | activity is no more than 0.10 MBq0.10\ \text{MBq}0.10 MBq |
Calculate the minimum activity the tracer must have when it is prepared.
The engineers prepare the tracer with an activity of 2.4 MBq2.4\ \text{MBq}2.4 MBq.
Explain whether this tracer meets both conditions.
97 exam-style questions on Edexcel GCSE Physics 6.5 Uses and dangers of radioactivity, covering 6.5.1 Uses of radioactivity, 6.5.2 Dangers of ionising radiation and precautions, 6.5.3 Half-life and radiation dangers, 6.5.4 Safety precautions for radiation exposure, and 6.5.5 Contamination and irradiation. Each one has a worked solution and a mark scheme showing where the marks go.