Work through these eight questions in order. They cover all four lessons in nuclear energy.
The timed practice session builder can turn the set into a timed run.
Questions
Question 1 (3 marks). Radiation A is stopped by a sheet of paper. Radiation B passes through paper but is stopped by a few millimetres of aluminium. Radiation C needs thick lead to reduce it.
Name A, B and C.
Answer
A is alpha, B is beta and C is gamma. The order of penetration is alpha, then beta, then gamma, so the thicker the material needed to stop it, the more penetrating the radiation.
Question 2 (2 marks). A technician works near a gamma source. State two ways to reduce the dose she receives.
Answer
Any two of these: keep a lead or thick concrete shield between her and the source, stay far from the source, and spend as little time near it as possible. Each control answers one property of the radiation: shielding answers penetration, distance answers spreading, and short time answers total exposure.
Question 3 (3 marks). A sample has 80 g of a radioactive isotope with a half-life of 6 days. What mass remains after 18 days?
Answer
18 ÷ 6 = 3 half-lives. Halve three times: 80 → 40 → 20 → 10 g.
Question 4 (3 marks). The table shows the count rate of a source.
| Time (h) | 0 | 4 | 8 | 12 |
|---|---|---|---|---|
| Count rate (counts per minute) | 960 | 480 | 240 | 120 |
Find the half-life.
Answer
The count rate falls from 960 to 480 in the first 4 hours, which is one halving. It falls from 480 to 240 in the next 4 hours, and again from 240 to 120. The halving time is steady, so the half-life is 4 hours.
Question 5 (3 marks). Use the data in Question 4 to predict the count rate at 20 hours. State your assumption.
Answer
20 ÷ 4 = 5 half-lives. Halve from 960 five times: 480, 240, 120, 60, 30 counts per minute.
The assumption is that the readings are for the source alone. Background radiation is ignored, and the half-life stays constant.
Question 6 (3 marks). A student measures 75 counts per minute near a source. With the source removed, the detector reads 15 counts per minute.
The half-life of the source is 10 minutes. What reading should she expect 10 minutes later?
Answer
Correct for background first: 75 − 15 = 60 counts per minute from the source. After one half-life, the source gives 60 ÷ 2 = 30.
The detector still picks up the background, so the reading is 30 + 15 = 45 counts per minute.
Question 7 (3 marks). A nuclear power station and a coal power station both produce electricity. State one similarity and one difference in how they release energy.
Answer
Similarity: both use the heat released to turn water into steam, and the steam turns a turbine connected to a generator.
Difference: a nuclear station gets its heat from the splitting of uranium nuclei (nuclear fission), while a coal station gets heat from burning coal in a chemical reaction that also releases carbon dioxide.
Question 8 (3 marks). A newspaper writes: “The waste has a half-life of 5 years, so after 10 years it is completely safe.” Use the half-life idea to evaluate the statement.
Answer
10 ÷ 5 = 2 half-lives, so the activity falls to 1/2 × 1/2 = 1/4, which is 25% of the original. The statement is wrong because 25% still remains.
A decaying source never reaches zero in a fixed number of half-lives. Whether a level is safe depends on the amount and the radiation type, not on the half-life alone.
If you got these wrong
Questions 1 and 2 test distinguishing radiation types and discussing safety controls conceptually. Questions 3 to 6 and 8 test interpreting half-life data. Question 7 tests comparing energy-generation principles.
Log each slip in the mistake log and paper error review and redo the question a few days later. To work through the gaps with a teacher, see online one-to-one Science tuition.