AQA GCSE Physics Physics Paper 1 (Foundation), November 2020: Question 5

✅ Correct Answer

radiotherapy

💡 Key Knowledge

• Background radiation comes from natural sources (rocks, cosmic rays, radon gas) and man-made sources (medical procedures like radiotherapy/X-rays, and fallout from nuclear weapons/power).
• Cosmic rays, rocks, and stars are all natural sources.

❌ Common Errors

Confusing cosmic rays (high-energy particles originating from outer space) with man-made medical applications.

✅ Correct Answers

1. An unstable nucleus absorbs a neutron and splits into two parts.

2. Two or three neutrons are released, as well as energy and gamma rays .

💡 Key Knowledge

• Nuclear fission is the splitting of a large, unstable nucleus (e.g., Uranium-235).
• It usually starts when the nucleus absorbs a slow-moving neutron.
• The products are two smaller daughter nuclei, a few fast neutrons, and a large amount of energy (released as kinetic energy and gamma radiation).

🧠 Exam Technique

Always select terms directly from the provided word box. "Energy" and "gamma rays" can be written in either order for the final two gaps.

✅ Correct Answer

Tick: An alpha particle is the same as a helium nucleus.

💡 Key Knowledge

An alpha particle consists of 2 protons and 2 neutrons, represented as ⁴₂He—identical to a helium nucleus. The equation shows plutonium-239 decaying into uranium-235 plus a helium nucleus (⁴₂He).

❌ Common Errors

Assuming the atomic number (94) or mass number (235) describes the alpha particle directly, rather than recognising the symbol ⁴₂He as a helium nucleus.

✅ Correct Answers

05.4: 24 000 years (accept 24 000 to 24 500)

05.5: 24 000 years (or matches your answer to 05.4)

📐 Step-by-Step Calculation

1. Find initial activity: Look at the y-axis at time = 0. Initial activity = 10 000 Bq.
2. Calculate half-activity: Half of 10 000 Bq is 5 000 Bq.
3. Read from graph: Locate 5 000 Bq on the y-axis, move across to the curve, and read straight down to the x-axis. The time corresponds to 24 000 years.
4. Identify Half-Life: Half-life is the time taken for the activity of a radioactive sample to halve. Therefore, the half-life is also 24 000 years.

🧠 Exam Technique

Use a sharp pencil and a ruler to draw construction lines from 5 000 Bq on the y-axis across to the curve and down to the x-axis to avoid parallax errors. Always check scale grid divisions carefully (each small square on the x-axis represents 1 000 years).

✅ Correct Answers (Any one of):

• Irradiation
• Cancer
• Genetic damage
• Mutations to DNA / genes
• Radiation sickness / poisoning

💡 Key Knowledge

Radioactive waste emits ionising radiation. Exposure can damage living tissue, kill cells, or cause mutations in DNA that lead to cancerous tumours.

❌ Common Errors

Vague answers like "it is dangerous" or "it kills you" without specifying biological impacts like cancer, cell mutation, or radiation sickness.