A point-like gamma radiation source is used to inspect welds in a steel structure. For radiation safety, a perimeter must be established where the dose equivalent rate does not exceed 2.5 μSv h−12.5\text{ }\mu\text{Sv h}^{-1}2.5 μSv h−1. At a distance of 1.5 m from the source, a radiation monitor detects a dose equivalent rate of 360 μSv h−1360\text{ }\mu\text{Sv h}^{-1}360 μSv h−1.
Assuming no shielding or absorption by the air, what is the minimum radius of the safety perimeter?
216 m216\text{ m}216 m
144 m144\text{ m}144 m
18 m18\text{ m}18 m
324 m324\text{ m}324 m
94 exam-style questions on Edexcel GCSE Physics 6.5 Uses and dangers of radioactivity. Each one has a worked solution and a mark scheme showing where the marks go.