Ionising Radiation and Risk

What Ionising Radiation and Risk covers

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.

The 8 subtopics

Each one has its own page.

• The nature of ionising radiationsRecall 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.Open →
• Effects on living tissue and radiation safetyRecall 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.Open →
• Absorbed dose, effective dose and riskRecall 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.Open →
• Binding energy and nuclear stabilityRecall 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.Open →
• The Nuclear Valley and modes of decayRecall 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.Open →
• Fission, fusion and nuclear powerRecall 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.Open →
• Activity, half-life and the decay constantRecall 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.Open →
• Investigating absorption and half-lifeRecall 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.Open →

What you need to know

Answer each one before you reveal it.

Take Ionising Radiation and Risk further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Ionising power vs Penetrating power

  Ionising power: how strongly a radiation strips electrons from the atoms it passes, greatest for alpha because it carries twice the charge of beta and moves comparatively slowly. Penetrating power: how far a radiation gets into matter before it is absorbed, greatest for gamma, while alpha is stopped by a sheet of paper and beta by a few millimetres of aluminium.

• Gray vs Sievert

  Gray: the unit of absorbed dose, one joule deposited in each kilogram of the absorbing material. Sievert: the unit of effective dose, the absorbed dose multiplied by the quality factor for how damaging that kind of radiation is to living tissue.

• Mass defect vs Binding energy

  Mass defect: the amount by which a nucleus is lighter than the separate nucleons that make it up, quoted in u or kg. Binding energy: the work that would be needed to pull a nucleus completely apart into its separate nucleons, quoted in J or MeV.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is meant by ionisation?

   Model answer

   Ionisation is the removal of one or more electrons from a neutral atom or molecule, leaving it as a charged ion.

2. 2

   What is an alpha particle?

   Model answer

   An alpha particle is a helium nucleus, consisting of two protons and two neutrons, with a charge of +2e and a mass of about 4 u.

3. 3

   What is a beta-minus particle?

   Model answer

   A beta-minus particle is a fast-moving electron emitted from the nucleus when a neutron changes into a proton.

4. 4

   What is a gamma ray?

   Model answer

   A gamma ray is a high-energy photon of electromagnetic radiation emitted when a nucleus loses excess energy, and it carries no charge and no mass.

5. 5

   Rank alpha, beta and gamma radiation in order of ionising power, and explain the order.

   Model 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.

6. 6

   State the absorber needed to stop each of alpha, beta and gamma radiation.

   Model answer

   Alpha radiation is stopped by a sheet of paper or a few centimetres of air, beta radiation by a few millimetres of aluminium, and gamma radiation is only reduced, needing several centimetres of lead to cut it substantially.

What is inside Levo

Six ways to work the same material.

Ionising Radiation and Risk revision questions

What does Ionising Radiation and Risk cover in OCR A-Level Physics B?

8 subtopics: 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. Each one has its own page with questions and model answers.

How is Ionising Radiation and Risk organised?

By the OCR H557 specification, subtopic by subtopic, so it matches the order you are taught it in.