The table below shows the percentage contribution of four major sources to the average annual background radiation dose in a certain region.
| Source | Percentage of total background radiation (%) |
|---|---|
| Radon gas (in the air) | 51 |
| Rocks and building materials | 15 |
| Cosmic rays | 12 |
| Food and drink | 9 |
Which percentage of background radiation comes from all other sources combined?
13%13\%13%
15%15\%15%
23%23\%23%
87%87\%87%
44 exam-style questions on CIE IGCSE Physics 5.2.1 Background radiation and measuring count rate. Each one has a worked solution and a mark scheme showing where the marks go.