GCSE Physics practice questions on radioactive decay and half-life. Try 3 for free below — with hints, the answer and why the wrong answers are tempting. GCSE Beast has 22 questions on this topic, from first steps to the hardest exam-style problems.
A glowing emergency exit sign contains tritium (hydrogen-3) gas sealed in glass tubes. The tritium emits β-particles that make a coating glow. The half-life of tritium is 12 years.
Which statement about the tritium in the sign 48 years after it was made is correct?
Natural cobalt is cobalt-59, which is stable: its nucleus has 27 protons and 32 neutrons. The cobalt-60 used to sterilise medical equipment is radioactive: its nucleus has 27 protons and 33 neutrons. Cobalt-60 decays by β-emission.
Which row explains why cobalt-60 is unstable and describes the effect of the β-decay?
| cobalt-60 has | the β-decay makes the number of neutrons | |
|---|---|---|
| A | too few neutrons | decrease |
| B | too few neutrons | increase |
| C | too many neutrons | decrease |
| D | too many neutrons | increase |
A technician at a calibration laboratory measures four samples E, F, G and H, each a different radioactive isotope. Each sample is measured at the start and again 12 hours later, with the same detector in the same position. The readings in the table include the background count rate, which is 30 counts / min.
| sample | count rate at the start (counts per minute) | count rate 12 hours later (counts per minute) |
|---|---|---|
| E | 720 | 90 |
| F | 630 | 230 |
| G | 830 | 100 |
| H | 990 | 150 |
Which sample has a half-life of 4.0 hours?