Science · Year 2 · Light and Shadows · Term 4

Blocking Light to Make Shadows

Students will explore how opaque objects block light to create shadows.

• ACARA Content Descriptions
• AC9S2U03

About This Topic

Blocking light with opaque objects creates shadows, central to the Year 2 light and shadows unit. Students discover that light travels in straight lines from sources like torches or the sun. An opaque object stops these rays, forming a dark patch, or shadow, on a surface behind it. They compare shadows from spheres, blocks, and cutouts, seeing how object shape defines shadow outline. Key investigations include predicting and observing how shadows grow larger and sharper when objects move closer to the light source.

This content meets AC9S2U03 by building skills in fair testing, observation, and causal explanation. It connects physical properties of materials to everyday experiences, such as tree shadows at recess or headlamp beams at night. Early grasp of light rays supports future topics in waves and energy transfer.

Active learning suits this topic perfectly. Simple setups with torches, objects, and screens allow instant prediction and testing. Students manipulate variables like distance and shape, observe results firsthand, and discuss in pairs. This approach makes invisible light paths visible, corrects errors through evidence, and sparks curiosity about the world.

Key Questions

1. Explain what causes a shadow to form.
2. Compare the shadows created by different shaped objects.
3. Predict how moving an object closer to a light source affects its shadow.

Learning Objectives

• Explain how opaque objects prevent light from passing through, thereby creating a shadow.
• Compare the shapes of shadows cast by objects with different geometric forms.
• Predict how the size of a shadow changes when the object casting it moves closer to or further from a light source.
• Identify the light source, the opaque object, and the shadow in a given scenario.

Before You Start

Properties of Light

Why: Students need a basic understanding that light travels and can be blocked to comprehend shadow formation.

Basic Shapes

Why: Comparing shadow shapes requires students to recognize and name common geometric forms.

Key Vocabulary

Opaque	An object that does not allow light to pass through it. Opaque objects block light, which causes shadows to form.
Shadow	A dark area formed when an opaque object blocks light. The shadow's shape is usually similar to the shape of the object blocking the light.
Light Source	Something that produces light, such as the sun or a lamp. Light travels in straight lines from the light source.
Transparent	An object that allows light to pass through it completely. Transparent objects do not cast distinct shadows.
Translucent	An object that allows some light to pass through but scatters it. Translucent objects cast fuzzy or indistinct shadows.

Watch Out for These Misconceptions

Common Misconception

Shadows stay the same size as the object.

What to Teach Instead

Shadow size depends on object distance from the light; closer means larger due to spreading rays. Pairs testing distances with rulers see measurements grow, building evidence against fixed ideas. Group charts reveal patterns clearly.

Common Misconception

All objects block light equally.

What to Teach Instead

Opaque objects block fully, translucent partly, transparent not at all. Hands-on tests with plastics and fabrics show shadow strength varies. Peer comparisons during rotations correct overgeneralizations through shared evidence.

Common Misconception

Shadows form because light bends around objects.

What to Teach Instead

Light travels straight, blocked by objects to cast shadows. Torch experiments with straight edges prove no bending. Student predictions followed by observations replace curve ideas with ray models via discussion.

Active Learning Ideas

Torch Distance Challenge: Shadow Sizes

Pairs set up a torch, object, and screen in a dark space. Place the object at three distances from the torch, predict shadow size each time, then measure with rulers. Record results in a class chart and explain patterns.

35 min·Pairs

Shape Shadow Match-Up: Object Gallery

Small groups project shadows of various objects like balls, sticks, and leaves onto paper using torches. Mix projections on a wall, then match each shadow to its object. Note how edges transfer from object to shadow.

40 min·Small Groups

Outdoor Stick Shadows: Time Tracking

Whole class places identical sticks in sunny spots and marks shadow tips with chalk every 15 minutes. Measure lengths, sketch changes, and predict next positions. Compare morning and afternoon data.

45 min·Whole Class

Puppet Shadow Play: Prediction Game

Individuals craft simple puppets from card, then pairs use torches to test shadow predictions by changing distance or angle. Perform short shows, noting size shifts. Share best observations.

30 min·Pairs

Real-World Connections

• Stage lighting designers use spotlights and opaque props to create specific shadow effects for theatrical performances, influencing the mood and storytelling.
• Architects and urban planners consider how buildings and trees cast shadows on public spaces, impacting sunlight availability for parks and pedestrian areas throughout the day.
• Photographers use light sources and objects to control shadows, shaping the appearance of their subjects and creating artistic compositions.

Assessment Ideas

Quick Check

Provide students with a flashlight, various opaque objects (e.g., a block, a toy animal, a cutout shape), and a blank wall or screen. Ask them to hold up an object between the flashlight and the wall and observe the shadow. Then, ask: 'What happens to the shadow when you move the object closer to the light? What happens when you move it further away?'

Discussion Prompt

Show students a picture of a sundial. Ask: 'How does a sundial work? What is blocking the light to make the shadow move? What do you think would happen to the shadow if the sun suddenly disappeared?'

Exit Ticket

Give each student a piece of paper. Ask them to draw a simple picture showing a light source, an opaque object, and the shadow it creates. Have them label each part. Then, ask them to write one sentence explaining why the shadow is there.

Frequently Asked Questions

What causes shadows in Australian Curriculum Year 2 science?

Shadows form when opaque objects block straight-traveling light rays from sources like the sun or torches, creating dark areas on surfaces. Students explain this through AC9S2U03 by observing torch setups and comparing everyday examples. Key is recognizing light stops at the object, not passing through.

How does moving an object affect shadow size?

Closer to the light source, shadows enlarge and sharpen as rays diverge more before hitting the screen. Farther away, they shrink and blur. Year 2 activities with rulers quantify this, helping students predict and graph changes reliably.

Why do different shapes make different shadows?

Shadow outlines match the object's silhouette because light rays trace straight paths around edges. Balls yield round shadows, sticks linear ones. Matching games with cutouts reinforce how shape transfers directly, building shape recognition skills.

How does active learning help Year 2 students understand shadows?

Active setups like torch stations let students predict, test distances, and measure shadows immediately, turning theory into evidence. Pair discussions correct errors on the spot, while outdoor tracking connects sun shadows to concepts. This hands-on cycle boosts retention, confidence, and explanation skills over passive lessons.