All lessons › Light and shadows › Lesson 2
Australian primary science · Year 5 · Lesson 2 of 3
Light in straight lines
Inquiry question: Can light go around corners?
Check practical materials
Testing an idea
What students learn
Light travels in straight lines. That is why it can’t go around opaque objects and why shadows form. Materials can be transparent, translucent or opaque.
Success criteria
- I can make a prediction with a reason.
- I can use the card test as evidence that light travels in straight lines.
- I can sort materials as transparent, translucent or opaque using evidence.
Preparation and materials
Before this lesson: Students know opaque objects make shadows (lesson 1).
- Small LED torch (cheap ones from a discount shop are fine) — 13
- Cardboard rectangles about 10 × 15 cm, cut from cereal boxes — 39 (3 per pair)
- Hole punch or sharp pencil (teacher use) — 1
- Plasticine or Blu Tack to stand the cards up (or fold a tab at the bottom) — 13 small lumps
- String or wool, about 60 cm — 13 pieces
- Test materials: baking paper, cling wrap, aluminium foil, tissue paper, cardboard, a clear plastic cup — 13 sets
- White paper as a screen — 13 sheets
- Bendy drinking straws (extension) — 13
Teacher setup
- Stack three cards and punch one hole through all of them together, about 5 cm from the bottom, so the holes line up.
- Cut the test materials into pieces about the size of a hand.
- Darken the room a little (blinds down) so torch spots are easy to see.
Safety and adaptations
- Never shine a torch into anyone’s eyes, including your own. Point beams at the cards, the table or the paper screen.
- Do not look straight into the torch, even through the holes: look at the spot on the paper instead.
- Use torches only; no laser pointers.
- Keep cling wrap away from faces.
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.
- Part A: stand the three cards in a line and check the holes with tight string.
- Predict, then shine the torch through the holes onto the paper. Look for the spot.
- Move the middle card 1 cm sideways. Predict, test and record.
- Part B: predict whether each material lets light through. Hold it between the torch and the paper.
- Record what you see and sort each material as transparent, translucent or opaque.
Teacher modelling prompt
Model the card test: “I stand the three cards in a row with the holes lined up. I check with the string: if the string goes through all three holes and is pulled tight, the holes are in a straight line. I shine the torch through the first hole and look for a spot on the paper, not into the torch.” Then predict aloud what will happen if one card moves 1 cm.
Record and explain evidence
Recording question: Can light go around corners, and which materials let it through?
| What we tested | Prediction | What we saw on the paper | What this tells us about light |
|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
What could we do to test whose idea is right?
Check understanding
What should pupils know? How does the three-card test show that light travels in straight lines?
Explain with evidence: Why does baking paper make a pale shadow but cardboard makes a dark one?
Apply the idea: Which material would you choose for a bathroom window that lets light in but stops people seeing in? Why?
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.