MYP Physics · 13 · investigation
Investigate an automatic night-light sensor
Electricity · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- discriminating
- Marks
- 8
- Topics
- 1
- Answer
- Complete
A light-dependent resistor (LDR) will control a night light. A team has an LDR, a multimeter, a lamp with a dimmer, a metre rule, and a phone light-meter app. They want to determine how LDR resistance depends on illuminance.
- a
Formulate Write a focused research question and a testable hypothesis.
2 marks - b
Design Design a method that would produce a useful graph and valid evidence.
4 marks - c
Evaluate Explain why lamp distance alone is not a sufficient measure of the light reaching the LDR.
2 marks
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a
Formulate Write a focused research question and a testable hypothesis.
Turn the task into a measurable method: name the independent, dependent and controlled quantities; describe apparatus and repeats; then explain how the evidence will be processed and how uncertainty or safety will be managed.
- 1
Writes a question linking measured illuminance to LDR resistance with other conditions controlled.
- 2
Predicts that resistance decreases as illuminance increases, with a defensible physical or component-based reason.
b
Design Design a method that would produce a useful graph and valid evidence.
Turn the task into a measurable method: name the independent, dependent and controlled quantities; describe apparatus and repeats; then explain how the evidence will be processed and how uncertainty or safety will be managed.
- 1
Collects paired illuminance and resistance readings across at least five well-spaced light levels.
- 2
Uses repeats and a mean at each light level.
- 3
Controls relevant variables such as sensor angle, lamp spectrum, ambient light, and LDR temperature.
- 4
Plots resistance against illuminance with units and selects scales that reveal the relationship.
c
Evaluate Explain why lamp distance alone is not a sufficient measure of the light reaching the LDR.
Turn the task into a measurable method: name the independent, dependent and controlled quantities; describe apparatus and repeats; then explain how the evidence will be processed and how uncertainty or safety will be managed.
- 1
Explains that reflected light, ambient light, source geometry, and lamp output affect illuminance as well as distance.
- 2
Concludes that illuminance should be measured at the LDR rather than inferred from distance alone.
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