Level 2 · Secondary physics teaching kit · Grades 10–12
Introductory nuclear physics and reaction evidence
Use the learner record during the live investigation, then use the instructor guide to facilitate comparison, address misconceptions, and assess evidence-bounded reasoning.
Learner lab record
Reaction yield and detector-efficiency audit
How do beam rate, target thickness, cross section, and detection efficiency combine into an expected count rate?
Setup
Use the reaction-yield laboratory. Begin in the thin-target regime, vary one factor at a time, and keep physical reaction yield separate from detector counts.
Predict first
- 1. Predict the yield response to doubling beam rate in the thin-target limit.
- 2. Predict what detector efficiency changes and what it leaves unchanged.
| Variable | Role | Unit |
|---|---|---|
| Beam particle rate | independent | particles/s |
| Target areal density | independent | nuclei/area |
| Reaction cross section | model input | area |
| Reaction and detected rates | dependent | events/s and counts/s |
Observation columns
Analyze
- 1. Which runs demonstrate linear scaling?
- 2. When would the thin-target approximation fail?
- 3. Why are counts not automatically proof of the proposed reaction channel?
- 4. Name two background or calibration controls.
Conclusion frame
Changing ___ by a factor of ___ changed modeled reaction rate by ___; detection efficiency changed ___ but not ___.
Instructor guide · 50–60 minutes
Teach the investigation, not the interface
Learning target: Learners construct a reaction-yield ledger and separate modeled physical events from detector acceptance, backgrounds, and identification.
Prepare
- • Review scientific notation and area units.
- • State the thin-target approximation.
- • Prepare one background-only and one calibration run.
Facilitation moves
- • Ask what happens in the target before what appears in the detector.
- • Require dimensional checks.
- • Keep channel identification separate from total count excess.
Accessibility and participation
- • Translate powers of ten into factor language.
- • Use a flow diagram from beam to target to detector.
- • Provide unit cards and calculator support.
Evidence of learning
- • A dimensionally consistent yield ledger
- • Correct efficiency separation
- • A credible background-control plan
Misconception checks
Every detector count is a nuclear reaction.
Counts include backgrounds and acceptance effects; channel identification requires calibrated signatures and controls.
Cross section is the physical size of a nucleus.
It is an interaction-probability measure with area units, not usually a geometric silhouette.
Extension
Add target attenuation and compare the exact thick-target expression with the linear approximation.