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%
484 exam-style questions on CIE IGCSE Physics 5.2 Radioactivity, covering 5.2.1 Background radiation and measuring count rate, 5.2.2a Alpha, beta and gamma emission, 5.2.2b Deflection and ionising effects of nuclear radiation, 5.2.3a Radioactive decay, 5.2.3b Effects of decay on the nucleus and decay equations, 5.2.4a Half-life, 5.2.4b Choosing isotopes for applications, and 5.2.5 Effects of ionising radiation and safety precautions. Each one has a worked solution and a mark scheme showing where the marks go.