The questions are on the radioactivity test. Take it under real conditions before reading the mark scheme.
Quick answer: Radioactivity is the random decay of unstable nuclei, which emit alpha particles, beta particles or gamma rays. This mark scheme gives the model answers and the marks for the 8 questions of the Physics 9-10 test on radioactivity, from stopping radiation to beta particles, with the equivalent answers to accept.
Model answers show the working that earns method marks. Allow follow-through if a wrong value from an earlier part is used correctly in a later part, and accept equivalent wording in the explanations.
Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: HS-PS1-8, GCSE P4
Question 1 Stopping radiation (2 marks)
Alpha is stopped by paper. Gamma needs thick lead (or concrete) to reduce it.
Marking: 1 mark for each correct radiation.
Question 2 Alpha decay equation (3 marks)
Mass number 234 − 4 = 230; atomic number 92 − 2 = 90; the nucleus is thorium-230.
Marking: 1 mark for each of the mass number, the atomic number and the name.
Question 3 Half-life calculation (3 marks)
Number of half-lives = 36 ÷ 12 = 3. Activity: 2400 → 1200 → 600 → 300 Bq.
Marking: 1 mark for 3 half-lives, 1 mark for halving three times, 1 mark for the answer with unit.
Question 4 Reading the decay graph (3 marks)
- The activity falls from 640 kBq to 320 kBq in 5 minutes.
- 15 minutes is 3 half-lives: 640 → 320 → 160 → 80 kBq.
- 640 → 320 → 160 → 80 → 40 → 20 is 5 half-lives: 5 × 5 = 25 minutes.
Marking: 1 mark for each part.
Question 5 Irradiation and contamination (3 marks)
Irradiation is exposure to radiation from a source outside the body. Contamination is when radioactive atoms get on or inside the body. To avoid contamination, wear gloves, do not eat or drink near sources, and wash hands after handling.
Marking: 1 mark for irradiation, 1 mark for contamination, 1 mark for a precaution.
Question 6 Fission and fusion (2 marks)
Fission is used in nuclear power stations. Fusion takes place in the Sun.
Marking: 1 mark for each.
Question 7 Choosing a tracer (2 marks)
The 6-hour isotope loses its activity quickly, so the patient receives a low total dose and the radiation soon becomes negligible. A 6-year isotope would stay radioactive in the patient for a long time and give a larger dose.
Marking: 1 mark for the lower dose or faster decay, 1 mark for the longer exposure with the 6-year isotope.
Question 8 Beta particles (2 marks)
A beta particle is a fast-moving electron. It is produced when a neutron in the nucleus changes into a proton, and the electron is emitted.
Marking: 1 mark for an electron, 1 mark for a neutron changing into a proton.
