Ionising Radiation and Risk | OCR A-Level Physics B (Advancing Physics) (H557)
Ionising Radiation and Risk
- 111 questions
- 8 subtopics
- The physics content, examined on all three papers
- Component 01, Component 02 and Component 03
Ionising Radiation and Risk is examined in all three written papers — the specification states that Components 01, 02 and 03 each assess content from across all the teaching modules, so nothing is confined to one paper.
It covers the nature of ionising radiations, effects on living tissue and radiation safety, absorbed dose, effective dose and risk, binding energy and nuclear stability, the Nuclear Valley and modes of decay, fission, fusion and nuclear power, activity, half-life and the decay constant and investigating absorption and half-life.
Sample questions from Ionising Radiation and Risk
Answer each one closed book first, then open the answer.
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The nature of ionising radiations
Rank alpha, beta and gamma radiation in order of ionising power, and explain the order.
Show the answer
Alpha is the most ionising, then beta, then gamma, because the alpha particle carries twice the charge of a beta particle and moves comparatively slowly, so it interacts strongly with the electrons it passes. -
Effects on living tissue and radiation safety
State three precautions taken when handling a radioactive source in a school laboratory.
Show the answer
The source is handled with long tongs and never with bare hands, it is pointed away from anyone present, and it is kept out of its lead store for the shortest possible time. -
Absorbed dose, effective dose and risk
Write the relationship between effective dose and absorbed dose.
Show the answer
The effective dose in sieverts is the absorbed dose in grays multiplied by the quality factor of the radiation concerned. -
Binding energy and nuclear stability
Calculate the energy equivalent of one unified atomic mass unit, in MeV.
Show the answer
E = mc² = 1.661 × 10⁻²⁷ × (3.00 × 10⁸)² = 1.49 × 10⁻¹⁰ J, which is about 934 MeV. -
The Nuclear Valley and modes of decay
Why do heavy stable nuclei need more neutrons than protons?
Show the answer
The electrostatic repulsion between protons acts across the whole nucleus while the strong attraction acts only between near neighbours, so extra neutrons are needed to add binding without adding repulsion. -
Fission, fusion and nuclear power
What is meant by the critical mass of a fissile material?
Show the answer
The critical mass is the smallest mass in which enough of the neutrons released are absorbed rather than escaping through the surface, so that the chain reaction is just self-sustaining. -
Activity, half-life and the decay constant
Write the relationship between half-life and decay constant.
Show the answer
The half-life is T½ = ln2/λ, so a large decay constant corresponds to a short half-life. -
Investigating absorption and half-life
In an absorption experiment, what result identifies the radiation as gamma?
Show the answer
A substantial count rate remains after several millimetres of aluminium, and increasing thicknesses of lead reduce it progressively without ever removing it completely.
The 8 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| The nature of ionising radiations | Recall questions on ionisation, the nature, charge and mass of alpha, beta-minus and gamma radiation, their ionising power, absorbers and ranges, why gamma is never fully absorbed, deflection in a magnetic field, the spread of beta energies, beta-plus radiation, and gamma emission after alpha or beta decay. | 14 |
| Effects on living tissue and radiation safety | Recall questions on how ionising radiation damages cells, direct and indirect damage, somatic and genetic effects, swallowed alpha emitters and external gamma sources, handling precautions, the inverse square fall with distance, lead and aluminium shielding, background radiation and the UK's 2.7 mSv annual dose, radiographers, weighing scans, short-lived tracers, and the ethics of medical use and radioactive waste. | 15 |
| Absorbed dose, effective dose and risk | Recall questions on absorbed dose and the gray, effective dose and the sievert, quality factors for alpha, beta and gamma radiation, absorbed and effective dose calculations, why two quantities and two unit names are needed, risk as probability times consequence, the chance of harm from an 8.0 mSv procedure, and the judgement involved in assessing risk. | 13 |
| Binding energy and nuclear stability | Recall questions on binding energy and mass defect, why a nucleus has less mass than its nucleons, the unified atomic mass unit and its energy equivalent, the mass defect, binding energy and binding energy per nucleon of helium-4, the binding energy curve and its peak near iron-56, fusion and fission from the curve, nucleon number, proton number and isotopes, and negative binding energy. | 14 |
| The Nuclear Valley and modes of decay | Recall questions on the Nuclear Valley and its axes, where stable nuclides lie, the changing neutron-to-proton ratio and why heavy nuclei need extra neutrons, which nuclides decay by beta-minus and beta-plus emission, how alpha and gamma emission move a nucleus, why the heaviest nuclei are unstable, binding energy after decay, and spontaneous and random decay. | 13 |
| Fission, fusion and nuclear power | Recall questions on nuclear fission and inducing it in uranium-235, the 200 MeV released and its mass equivalent, chain reactions and critical mass, moderators, control rods and coolants, nuclear fusion and why it needs high temperatures, deuterium–tritium fusion, why fusion releases more energy per kilogram, and the benefits and concerns of fission power. | 15 |
| Activity, half-life and the decay constant | Recall questions on activity and the becquerel, the decay constant, A = λN, half-life and T½ = ln2/λ, N = N₀e⁻λᵗ, calculating decay constants, activities and remaining fractions, the time to fall to one tenth, random decay giving a predictable pattern, why activity falls exponentially, and subtracting background. | 14 |
| Investigating absorption and half-life | Recall questions on investigating absorption with paper, aluminium and lead, measuring background, the results that identify alpha, beta and gamma radiation, keeping the distance fixed, long counting times and the √N uncertainty, safety with sealed sources, measuring the half-life of protactinium from a count rate graph or a logarithmic plot, and the sources of uncertainty. | 13 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR A-Level Physics B (Advancing Physics) Active Recall Guide
Every topic, not just this one. 2,455 questions with their answers.