Year 6 · Science · Physical sciences
Light and shadows
Students investigate how light travels in straight lines from a source, how shadows form, and how light reflects off and passes through different materials.
Awaiting educator review. This material was drafted by our content team with AI assistance and is waiting for review by a qualified educator. Please check it suits your child before using it. Created 10 October 2026.
These lessons were written around Australian Curriculum strands and matched to New Zealand year levels by age (NZ Year 1 is the first year of school). They are not yet mapped to The New Zealand Curriculum, so check them against your own learning programme.
Learning goals
Learners will
- Explain that light travels in straight lines from a light source.
- Explain how shadows form and change size.
- Classify materials as transparent, translucent or opaque.
Success looks like
- I can explain why a shadow forms.
- I can change the size of a shadow by moving an object or a torch.
- I can sort materials by how much light passes through them.
The big idea
Light comes from light sources such as the Sun, a torch or a campfire. The Moon is not a light source: it reflects light from the Sun.
Light travels in straight lines. You can see this when sunlight shines through gaps in clouds or trees in straight beams.
When an opaque object blocks light, it leaves a dark area behind it. This is a shadow. A shadow has the outline shape of the object.
The closer an object is to the light source, the bigger its shadow. Moving the object towards the wall makes the shadow smaller and sharper.
Materials let different amounts of light through. Transparent materials let most light through. Translucent materials let some through. Opaque materials block it.
Smooth, shiny surfaces like mirrors reflect light in a neat way, so we can see images in them. We see most objects because light reflects off them into our eyes.
Outdoors, shadows change during the day. In the middle of the day, when the Sun is high, shadows are short. Early and late in the day, when the Sun is low, shadows are long.
Worked examples
Changing shadow size
How can you make a toy's shadow on the wall bigger?
- Shine the torch at the wall in a dim room.
- Hold the toy between the torch and the wall.
- Move the toy closer to the torch and measure the shadow with a ruler.
- Move it closer to the wall and measure again.
Answer: Move the toy closer to the torch (or the torch closer to the toy) to make the shadow bigger.
Sorting materials
Sort clear plastic wrap, baking paper and cardboard.
- Shine the torch through each onto paper.
- Plastic wrap: bright light, you can see through clearly, so transparent.
- Baking paper: some fuzzy light gets through, so translucent.
- Cardboard: no light gets through, so opaque.
Answer: Plastic wrap is transparent, baking paper is translucent and cardboard is opaque.
Practice check
Have a go, then check your answers. Each answer comes with an explanation.
Answer guide for parents
Which of these is a light source?
A campfire — A campfire makes its own light. The Moon and mirrors only reflect light.
Why do shadows form?
An object blocks light travelling in straight lines — Light travels in straight lines, so an object blocks it and leaves a dark area.
When is your shadow shortest on a sunny day?
Around midday — The Sun is highest around the middle of the day, so shadows are shortest.
Baking paper lets some light through, but you cannot see clearly through it. It is…
Translucent — Letting some light through without a clear view is translucent.
How can you make a shadow on the wall smaller?
Move the object closer to the wall — Moving the object away from the light and closer to the wall makes a smaller shadow.
A material that lets no light through is called o_____.
opaque — Opaque materials block light completely.
Light bounces off a mirror. What is this called?
reflection — Light bouncing off a surface is reflection.
Does light travel in straight lines or curved lines?
straight — Light travels in straight lines, which is why shadows form.
Watch out for
- Many students think the Moon makes its own light. It reflects sunlight.
- Some think a shadow is a reflection or 'belongs' to the object. A shadow is simply an area where light is blocked.
- Some think we see by light leaving our eyes. We see when light enters our eyes.
Tips for parents
- Darken the room as much as possible so shadows are crisp.
- Turn shadow play into a puppet show using cardboard cut-outs of Australian animals.
- Safety: never look directly at the Sun or shine torches or mirrors into anyone's eyes; handle glass jars carefully.
Go further
- Make a shadow clock: stand a stick in the ground and mark the end of its shadow every hour on a sunny day.
- Use two mirrors to send torch light around a corner.
- Design a sun hat using opaque, translucent and transparent materials and explain which works best.