All lessons › Lights out for turtles › Lesson 3
Australian primary science · Year 5 · Lesson 3 of 3
Design a turtle-safe light
Inquiry question: Can we shield a light so it lights a path but can’t be seen from a turtle’s eye level?
Check practical materials
Fair testing
What students learn
Because light travels in straight lines, an opaque shield can stop light reaching places we don’t want lit while still lighting the ground below. We can design, test and improve a shield by observing where the light goes.
Success criteria
- I can pose a question and predict which shield will work best.
- I can test each design the same way and measure the lit patch.
- I can explain my results using the idea that light travels in straight lines.
Preparation and materials
Before this lesson: Students know light travels in straight lines and that shielded, downward lights help hatchlings (lessons 1 and 2).
- Phone torch, or any small torch (a few phones or torches shared between pairs is fine) — 4–13
- Paper or thin card for tubes and hoods — 26 sheets
- Paper or plastic cups (opaque) — 13
- Aluminium foil — 1 roll
- Sticky tape — 13 short lengths or shared rolls
- Rulers or a tape measure — 13
- Orange or red cellophane (optional, if the school has some) — A few pieces
Teacher setup
- Choose the darkest room available; cover windows with paper or blinds if possible.
- Mark a “path” on the floor with tape or chalk, and a “turtle eye” spot 2 metres away at floor level.
- Test one phone torch yourself first so you know how dark the room gets.
- Print one investigation record per pair.
Safety and adaptations
- Never shine a torch into anyone’s eyes.
- Keep walkways clear before dimming the lights; walk, don’t run, in the dark.
- If using a phone, the teacher holds or supervises it; phone torches can get warm.
Review your school policies and curriculum requirements before teaching.
How to investigate
The lesson sequence should leave pupils with evidence to interpret, not only an activity to finish.
- Pairs write a question and a prediction: which shield will hide the bulb from the turtle spot but still light the path?
- Make three designs: a short paper tube, a long paper tube, and a cup or foil hood. (Bare torch = no shield.)
- Keep it fair: same torch, same height (50 cm), pointing straight down, same turtle spot 2 m away.
- For each design, one partner looks from the turtle spot at floor level: can you see the bulb? The other measures the width of the lit patch on the floor.
- Improve your best design once and test it again. Optional: tape on orange cellophane and compare the colour of the light.
Teacher modelling prompt
Hold the bare torch about 50 cm above the floor, pointing down. Think aloud: “From the turtle spot, at floor level, I can see the bulb shining sideways. Now I slide a paper tube over it. If light travels in straight lines, the tube should block the line from the bulb to the turtle’s eye.” Have a student check from the turtle spot, then measure the lit patch.
Record and explain evidence
Recording question: Can we shield a light so it lights a path but can’t be seen from a turtle’s eye level?
| Design | Prediction | Bulb seen from turtle spot? (yes or no) | Width of lit patch on floor (cm) | Still lights the path? (yes or no) |
|---|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
Which claim fits our observations of the path?
Check understanding
What should pupils know? How does a shield stop a turtle from seeing a light?
Explain with evidence: The bare torch lit a patch 120 cm wide; the long tube lit a patch 40 cm wide. Explain why.
Apply the idea: Draw and label a turtle-safe light for the café path. Stretch (older students): what is one variable you did not control in our test, and how would you control it next time?
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.