Radioactivity | OCR GCSE Combined Science Physics, Higher tier (J250)
Radioactivity
- 105 questions
- 7 subtopics
- Paper 12 (Physics)
- Paper 12 (Physics)
Radioactivity is examined in Paper 12 (Physics).
It covers protons, neutrons and isotopes, unstable nuclei and the emissions they give out, balancing nuclear equations, electron energy levels, and radiation from atoms, half-life and the randomness of decay, penetration of alpha, beta and gamma and contamination and irradiation, and reducing the hazard.
Sample questions from Radioactivity
Answer each one closed book first, then open the answer.
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Protons, neutrons and isotopes
What is an isotope?
Show the answer
An isotope is an atom of an element that has the usual number of protons but a different number of neutrons. -
Protons, neutrons and isotopes
When a nucleus is written in the conventional way, what does the atomic number tell you?
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It gives the number of protons in the nucleus, which identifies the element. -
Unstable nuclei and the emissions they give out
What is the charge on an alpha particle?
Show the answer
It has a charge of +2, because it carries two protons and no electrons. -
Unstable nuclei and the emissions they give out
How do the mass and charge of a nucleus change when it emits gamma radiation?
Show the answer
Neither changes, because gamma emission removes only energy from the nucleus. -
Balancing nuclear equations
Which two totals must be the same on both sides of a nuclear decay equation?
Show the answer
The total mass number and the total charge must be the same on each side. -
Balancing nuclear equations
A polonium nucleus of mass number 218 and atomic number 84 decays by alpha emission. What is left behind?
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A nucleus of mass number 214 and atomic number 82, which is lead. -
Electron energy levels, and radiation from atoms
What charge does an atom have once it has lost an outer electron?
Show the answer
It has a positive charge, because it then has more protons than electrons. -
Electron energy levels, and radiation from atoms
Which has the higher frequency, gamma radiation or visible light?
Show the answer
Gamma radiation has by far the higher frequency.
The 7 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Protons, neutrons and isotopes | The particles in a nucleus and their charges and masses, what nucleons are, what an isotope is, and how mass number and atomic number give the neutron count and nuclear charge. | 21 |
| Unstable nuclei and the emissions they give out | Why unstable nuclei emit radiation, what alpha and beta particles, gamma rays and neutrons are and the charge each carries, and how the mass number and atomic number change with each emission, including why beta emission leaves the mass number unchanged. | 16 |
| Balancing nuclear equations | How alpha, beta, gamma, neutrons and protons are written in decay equations, which totals must balance, and worked examples for radium, carbon, uranium, polonium and iodine decays. | 16 |
| Electron energy levels, and radiation from atoms | Electrons in energy levels, excitation by absorbing radiation and emission on falling back, ionisation and the positive ion it leaves, the wide range of frequencies atoms and nuclei emit, gamma rays from the nucleus, the spectrum in order of frequency, and what sets the frequency emitted. | 16 |
| Half-life and the randomness of decay | Half-life in terms of nuclei and count rate, why decay is random yet a sample has a reliable half-life, finding a half-life from count rates and graphs, the net decline in activity as a ratio after several half-lives, activity calculations, and modelling decay with dice. | 18 |
| Penetration of alpha, beta and gamma | What absorbs alpha, beta and gamma radiation, which is most and least penetrating, which ionises most strongly, how far each travels in air, and reading absorption tests. | 10 |
| Contamination and irradiation, and reducing the hazard | The difference between irradiation and contamination, why irradiating an object does not make it radioactive, why contamination is the more serious long-term hazard, why alpha is most dangerous inside the body and gamma outside it, and how shielding, distance, time and careful handling reduce the risk. | 8 |
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 GCSE Combined Science Physics, Higher tier Active Recall Guide
Every topic, not just this one. 1,222 questions with their answers.