Year 1 · 40 minutes · Sensors
Can the same object become invisible to a sensor?
A light sensor measures a signal. Our detector compares that signal with a threshold. The signal depends on the object and its lighting. If the light changes, the same object may fall below the threshold. A sensor gives a measurement, not a complete account of the world.
Use a torch and a paper object to demonstrate light without pointing at eyes. Open the synthetic signal display and identify the fixed object pulse and background readings.
Explain the difference between an object and a picture of it. Useful earlier investigations: y1-branch Use pairs: one child chooses or points while the other traces or checks. Swap after one case. An adult records the child’s words; drawing and movement are equally valid evidence.
Australian Curriculum Version 9 · Digital Technologies: AC9TDI2K01, AC9TDI2P03. Selected aspects only. This activity contributes evidence; it does not cover the full descriptor or achievement standard. A programming descriptor is not claimed for merely moving controls. ACARA AI curriculum connection · V9 Technologies These are planning connections, not ACARA endorsement or exhaustive descriptor alignment.
Light a paper object and shade it. Describe what changes without moving the object.
Ask: “Did the object leave when it got darker?”
Listen for: “No, the light changed.”
Children mark whether the detector will still see the object at half brightness.
Ask: “What does the detector compare?”
Listen for: “The signal with the line.”
Move the light control in steps; observe the waveform and detected region. Keep the threshold fixed and record two readings.
Ask: “Which number changed while the object stayed?”
Listen for: “The measured light signal.”
Lower the threshold until the object reappears. Reveal a background spike.
Ask: “Can lowering the line cause a different mistake?”
Listen for: “It might see the background as an object.”
Choose a compromise threshold and test bright, shadowed and empty-background cases. Explain unresolved errors.
Ask: “Can your setting pass all three tests?”
Listen for: “Some signals overlap, so maybe not.”
Draw signal and threshold for one miss and one false alarm.
Ask: “How do we know this was a miss?”
Listen for: “The object was there but its signal was too low.”
Sensors see the whole world.
Halve illumination with object and threshold fixed. Predict whether the object pulse remains above the line.
Lowering the threshold recovers a shaded object but can also detect a background spike that is not the object.
Choose a threshold and document one correct detection, one miss and one false alarm across lighting conditions.
Look for an explanation involving measurement, not an object disappearing. Use the background spike to check whether the learner recognises two kinds of error.
Use a large printed signal with a movable string threshold. Students can point instead of reading decimal values.
Compare two sensors with independent background spikes and propose an agreement rule.
A detector setting with three annotated signal tests.
No cameras or microphones are used. Never shine a torch at eyes; the lab is a synthetic demonstration, not a safety detector.
Simulate many independently noisy readings at each illumination level and estimate detection and false-alarm rates with sample counts.
| Criterion | Beginning | Secure | Extending |
|---|---|---|---|
| Fair testing | Moves object and light together | Changes light with object fixed | Records comparable signal values |
| Error explanation | Says the sensor is bad | Connects a miss to the threshold | Explains the miss/false-alarm trade-off |
Australian Curriculum Version 9 · Digital Technologies
References: AC9TDI2K01, AC9TDI2P03. Read the current source (checked 2026-09-07).
Evidence to assess: A detector setting with three annotated signal tests.
Selected aspects only. This activity contributes evidence; it does not cover the full descriptor or achievement standard. A programming descriptor is not claimed for merely moving controls. Moderate the supplied illustrative responses against your school unit and current achievement standard.
These are planning estimates to test with your class. A short session develops one supported claim; it does not compress the whole senior project.
| Stage | 45 minute focus | 60 minute investigation |
|---|---|---|
| Readiness and prediction | 0–5 | 0–5 |
| Trace the supplied example | 5–13 | 5–15 |
| Author and run cases | 13–25 | 15–35 |
| Counterexample and redesign | 25–35 | 35–45 |
| Explain and discuss | 35–42 | 45–55 |
| Export and handover | 42–45 | 55–60 |
For a longer project, use three 50-minute sessions. Session 1 (0–50): readiness, model, hypothesis and initial cases. Export a project and record the next test. Session 2 (50–100): reopen, check settings, author counterexamples and revise the design. Export the changed project and identify unresolved evidence. Session 3 (100–150): independent peer test, final artefact, individual explanation and moderation. If using two 60-minute sessions, stop at minute 60 after saving the first comparison; use 60–120 for redesign, independent test and defence.
Entry check: Explain the difference between an object and a picture of it. Ask the learner to demonstrate it before choosing the level of support.
Preparation: allow about 10 minutes to run the starter, print the cards and check a project can be reopened. This estimate has not yet been measured in a classroom pilot.
For young learners, show one picture or case at a time. Accept pointing, movement, a drawing or adult transcription. Read the question aloud; explain the numeric model privately to the adult. Do not assess keyboard speed or independent reading.
For one device, use a projector: one pair predicts, one operates, and the class records on paper. Swap roles after the first comparison. For individual access, support keyboard controls and a written table equivalent to each visual. Learners may explain orally or with an annotated diagram. Never require personal data, a recorded voice, or a photograph.
Mixed readiness: if the entry check is difficult, use the linked prerequisite and the first two case cards; retain the same central question. If secure, ask the learner to design an unseen test and state which explanation it could disprove.
Multiply each reading by the light fraction and compare with the detector boundary. Count misses and false spots separately.
Starting parameters: Light percent = 100, Detector boundary = 0.5
5 cases calculated from your supplied inputs. Compare the evidence with your prediction.
| reading | signal | present | detected | miss | false spot |
|---|---|---|---|---|---|
| 1 | 0.12 | False | False | False | False |
| 2 | 0.72 | True | True | False | False |
| 3 | 0.68 | True | True | False | False |
| 4 | 0.8 | True | True | False | False |
| 5 | 0.13 | False | False | False | False |
These are authored examples, not work collected from children. Assess reasoning using the lesson rubric, not whether the first prediction was correct.
Beginning: “It worked because the result looks right.” This identifies no exact case, control or measurement. Ask the learner to point to one row and say what happened.
Developing: “In the first case I recorded reading: 1; signal: 0.12; present: False; detected: False; miss: False; false spot: False.” This cites evidence, but does not yet explain how the result follows from the rule. Ask the learner to trace the relevant step.
Secure: “For the first supplied case, reading: 1; signal: 0.12; present: False; detected: False; miss: False; false spot: False. I can trace it using this mechanism: Multiply each reading by the light fraction and compare with the detector boundary. Count misses and false spots separately. My result supports a claim about these supplied cases. It does not establish that the same result holds outside them.” Look for an accurate trace, the actual settings and a bounded claim; accept equivalent oral or visual evidence.
Extending: The learner constructs and reruns a new case, reports whether the first explanation survives, and defends a revised design. Use this concrete challenge: Use a torch and a paper object. Change the light, then explain what changed and what stayed there. Require the original and changed evidence and this boundary: The readings are a teaching model, not a calibrated camera or real sensor.
Moderation: first assess independently against each lesson criterion. Compare the exact trace or artefact that led to your judgement. Resolve differences using evidence, not polished language. Keep each learner's individual explanation even when the artefact was produced in a group.