Changing Shadows

Active learning helps students grasp abstract light behavior by letting them manipulate light, objects, and surfaces directly. When students change one variable at a time and observe shadows, they build lasting mental models of how light travels in straight lines and forms shadows.

• Year 3
• Science
• 4 activities
• 15 min–50 min

Learning Objectives

1. Design an experiment to investigate how the distance between a light source and an object affects shadow length.
2. Predict the change in shadow position and length throughout a day based on the apparent movement of the sun.
3. Explain how the angle of a light source influences the shape and size of a shadow.
4. Compare shadows cast by different opaque objects of similar size but varying shapes.
5. Identify the relationship between an object's position relative to a light source and the resulting shadow.

Decision Matrix

⏱ 25 min·Pairs

Pairs Experiment: Torch Shadow Sizes

Pairs set up a torch, toy figure, and white screen. Predict and test shadow length by moving torch closer or farther from figure. Measure and record changes in a results table, then swap roles to repeat.

Prepare & details

Predict what causes a shadow to change its size or shape throughout the day.

Facilitation Tip: During Torch Shadow Sizes, remind pairs to keep the toy and screen in the same positions while only changing the torch-to-toy distance.

Setup: Groups at tables with matrix worksheets

Materials: Decision matrix template, Option description cards, Criteria weighting guide, Presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management

Decision Matrix

⏱ 35 min·Small Groups

Small Groups: Angle Shadow Stations

Prepare four stations with torches at different heights and objects like sticks or hands. Groups rotate every 7 minutes, draw shadow shapes, note angle effects, and discuss predictions before rotating.

Prepare & details

Design an experiment to make a shadow longer or shorter.

Facilitation Tip: At Angle Shadow Stations, rotate student groups so each group tests three different torch angles with the same object and surface.

Setup: Groups at tables with matrix worksheets

Materials: Decision matrix template, Option description cards, Criteria weighting guide, Presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management

Decision Matrix

⏱ 50 min·Whole Class

Whole Class: Playground Shadow Tracker

Choose fixed objects like goalposts. Mark shadow tips with chalk at 10-minute intervals over break time. Class gathers to measure lengths, plot on graph paper, and predict afternoon positions.

Prepare & details

Explain how we can predict where a shadow will fall.

Facilitation Tip: During Playground Shadow Tracker, have students mark shadow tips with chalk at hourly intervals to clearly see length changes over time.

Setup: Groups at tables with matrix worksheets

Materials: Decision matrix template, Option description cards, Criteria weighting guide, Presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management

Decision Matrix

⏱ 15 min·Individual

Individual: Prediction Challenge Cards

Give cards with shadow scenarios and prediction spaces. Students test one using mini-torch setup, draw before/after, explain changes. Share one with partner for feedback.

Prepare & details

Predict what causes a shadow to change its size or shape throughout the day.

Setup: Groups at tables with matrix worksheets

Materials: Decision matrix template, Option description cards, Criteria weighting guide, Presentation template

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management

Teaching This Topic

Teachers should start with concrete, hands-on experiences before introducing abstract concepts. Avoid explaining shadow formation before students have observed it themselves. Research shows students learn best when they predict, test, and explain their findings in small cycles rather than receiving lectures upfront.

What to Expect

Students will explain that shadow size and position depend on the light source’s distance and angle to the object. They will use vocabulary like light ray, opaque object, and angle correctly in discussions and diagrams after completing the activities.

Watch Out for These Misconceptions

Common Misconception

During Torch Shadow Sizes, watch for students who assume shadows stay the same size regardless of torch position.

What to Teach Instead

Have students record torch-to-toy and toy-to-screen distances in a simple table, then compare shadow lengths to discover that closer torches make larger shadows.

Common Misconception

During Playground Shadow Tracker, watch for students who think the tree stretches to make longer shadows.

What to Teach Instead

Ask students to trace the tree’s outline alongside its shadow at each time mark to show the tree’s fixed size while the shadow changes.

Common Misconception

During Angle Shadow Stations, watch for students who draw shadows pointing toward the torch instead of away from it.

What to Teach Instead

Have students sketch the torch, object, and shadow on paper, then rotate the torch to different angles and adjust their sketches to correct the shadow direction.

Assessment Ideas

Quick Check

During Torch Shadow Sizes, provide a torch, small toy, and flat surface. Ask students to position the torch to make the toy's shadow as long as possible, then as short as possible. Listen for students to explain that shadow length changes with torch distance and angle.

Exit Ticket

After Angle Shadow Stations, ask students to draw a simple diagram showing a light source, an object, and its shadow. Have them write one sentence explaining how the shadow’s shape and size are determined by the light’s position and angle.

Discussion Prompt

During Playground Shadow Tracker, pose the question: 'If you were outside at noon and then again at 4 PM, how would the shadow of a tree likely change?' Encourage students to use terms like 'light source,' 'position,' and 'angle' in their explanations.

Extensions & Scaffolding

• Challenge students to create shadows that are twice as long as the object by adjusting torch distance and angle.
• For students who struggle, provide a ruler taped to the table and ask them to measure torch-to-screen distance and shadow length to see the relationship.
• Deeper exploration: Introduce flashlights with different beam widths to investigate how light spread affects shadow edges.

Key Vocabulary

opaque	An object that does not allow light to pass through it, causing a shadow to form behind it.
light source	Anything that emits light, such as the sun, a torch, or a lamp.
shadow	A dark area created when an opaque object blocks light from a light source.
light rays	Imaginary straight lines that show the path light travels from a source.