Nuclear physics: decay, reactions and binding
Key idea: Separate random single-nucleus behaviour from population laws, conserve every required quantity in reactions, and explain released energy through increased binding rather than disappearing mass.
Before you start: Quantum Physics objective chainMeasurement objective chain
By the end, you can
- Interpret nuclear structure, nuclides, random decay and radiation measurements.
- Evaluate radioisotope applications and hazards from physical properties.
- Balance nuclear reactions and use conservation to explain antineutrino evidence.
- Connect mass defect, binding energy and the binding-energy curve to fusion and fission.
Starting-point self-check
1. Check your starting point
Attempt all six groups without notes and mark the first structure, decay, risk, conservation, binding or curve decision you cannot justify. Use the recorded topic diagnostic above when you want scoring and a personalised repair plan.
Applications and hazards 20(l)
Question 1
Choose radiation for a thickness gauge and justify it using penetration, ionisation and half-life.
Check the model response
Beta is commonly suitable: partly absorbed by the sheet yet still detectable. Choose a half-life long enough for stable operation while controlling exposure; alpha is stopped too readily and gamma may be too penetrating.
repair
2. Repair the common breaks
Use only the correction matching an error, then retry the corresponding diagnostic.
Applications and hazards 20(l)
Check this idea
Misconception: More penetrating always means more dangerous.
Repair: Hazard depends on exposure route, ionisation, penetration, activity and time.
worked example
3. Follow six worked models
Follow how each solution uses evidence, corrected data, risk criteria, conservation or the binding-energy curve.
Applications and hazards 20(l)
Model 1
Compare alpha and gamma for an internal tracer.
Check the model response
Alpha is strongly ionising and weakly penetrating, producing high local dose and poor external detection. Gamma is penetrating and externally detectable; activity, chemical behaviour and a suitable half-life must also be controlled.
guided practice
4. Guided practice
Use each hint only to select the correct nuclear number, population relation, radiation property or energy comparison.
Applications and hazards 20(l)
Question 1
State one reason a very short half-life can be unsuitable for a permanent gauge.
Hint: Link half-life to operating time.
Check the model response
Activity changes too quickly, requiring frequent replacement and recalibration.
independent practice
5. Independent practice
Solve without repair notes and state background, conservation, exposure and curve assumptions.
Applications and hazards 20(l)
Question 1
Evaluate one medical and one industrial use against hazards.
Check the model response
Select radiation and half-life for penetration, detection and duration; then control time, distance, shielding, contamination and disposal. Benefit must be compared with ionising dose, not asserted from penetration alone.
Practice exit check
6. Practice assessment
Use this as extra closed-book practice, then complete the separate recorded assessment in your plan.
Applications and hazards 20(l)
Question 1
Why is half-life alone insufficient when choosing a source for imaging?
Check the model response
Penetration, ionisation, photon/particle type, detectability, chemical localisation, activity and dose also determine usefulness and hazard.
Re-test practice
7. Delayed re-test practice
Return after at least three days and solve these fresh contexts without reopening earlier responses. The recorded plan enforces the delay and uses a separate re-test family for selected-response skill-group evidence.
Applications and hazards 20(l)
Question 1
Why is alpha especially hazardous inside the body?
Check the model response
Its high ionising power deposits energy densely over a short range in tissue.