Science · Year 3 · Light and Shadows: Chasing the Sun · Summer Term

Changing Shadows

Students will investigate how the size and shape of shadows change depending on the light source and object position.

• National Curriculum Attainment Targets
• KS2: Science - Light
• KS2: Science - Working Scientifically

About This Topic

Shadows form when light from a source travels in straight lines and meets an opaque object that blocks it. In Year 3, students investigate how shadow length, width, and position change with the distance between light source, object, and surface, plus light angle. They predict daily shadow shifts from the sun's path, design experiments to lengthen or shorten shadows, and explain predictions using light ray models.

This topic fits the National Curriculum Light unit and Working Scientifically requirements, including fair testing, observation, and pattern spotting. Students build skills in variables control and data recording, connecting to real-world observations like flagpole shadows or sundials. It fosters prediction confidence and scientific explanations.

Active learning excels for shadows because effects appear instantly with simple tools. When students adjust torches on puppets or track outdoor shadows collaboratively, they see direct links between actions and results, refine predictions through trial, and use precise terms like 'light rays' naturally.

Key Questions

1. Predict what causes a shadow to change its size or shape throughout the day.
2. Design an experiment to make a shadow longer or shorter.
3. Explain how we can predict where a shadow will fall.

Learning Objectives

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

Before You Start

Properties of Light

Why: Students need to know that light travels in straight lines to understand how it can be blocked to form shadows.

Materials and Their Properties

Why: Understanding that some materials are opaque (block light) is fundamental to explaining shadow formation.

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.

Watch Out for These Misconceptions

Common Misconception

Shadows stay the same size as the object.

What to Teach Instead

Shadow size depends on light source distance to object and screen. Pair experiments with rulers show closer torches make larger shadows; students correct via their data tables and group shares.

Common Misconception

Shadows grow because objects stretch.

What to Teach Instead

Changes come from light angle and distance, not object movement. Outdoor tracking reveals fixed object shadows lengthening without stretching; discussions link observations to sun position.

Common Misconception

Shadows point away from the light source.

What to Teach Instead

Shadows fall opposite the light direction. Station rotations with varied torch angles help students map directions visually, adjusting mental models through sketches and peer checks.

Active Learning Ideas

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.

25 min·Pairs

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.

35 min·Small Groups

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.

50 min·Whole Class

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.

15 min·Individual

Real-World Connections

• Architects and urban planners use knowledge of shadow patterns to design buildings and public spaces, ensuring adequate sunlight and avoiding unwanted shade.
• Gardeners observe how the length and direction of shadows change throughout the day and year to determine the best locations for planting different types of vegetables and flowers.
• Historical sundials, like those found at ancient sites such as Stonehenge, demonstrate an early understanding of how the sun's changing position creates predictable shadow movements.

Assessment Ideas

Quick Check

Provide students with a torch, a small toy, and a flat surface. Ask them to position the torch to make the toy's shadow as long as possible, then as short as possible. Observe their actions and ask: 'What did you change to make the shadow longer?'

Exit Ticket

On a slip of paper, ask students to draw a simple diagram showing a light source, an object, and its shadow. Then, ask them to write one sentence explaining why the shadow is the shape and size it is.

Discussion Prompt

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.

Frequently Asked Questions

How do shadows change with light source distance?

Closer light sources to objects create longer, larger shadows on screens, while distant sources make shorter ones matching object size. Year 3 experiments use torches to test this: students predict, measure shadow lengths at 30cm, 60cm, 90cm distances, and graph results. This reveals inverse proportion patterns clearly.

What causes daily shadow changes?

As the sun moves from east to west, shadows shift position, lengthen at midday, and shorten later. Students track playground shadows hourly, noting direction flips. Predictions improve with simple models like stick puppets under lamps simulating sun paths, linking to Earth's rotation.

How can active learning help students understand changing shadows?

Active approaches like torch manipulations and outdoor hunts provide instant feedback on predictions. Students in pairs or groups test variables directly, observe effects, and discuss anomalies, building accurate mental models. Collaborative graphing of class data highlights patterns, while drawing shadows reinforces light ray concepts over passive watching.

How to design a fair test for shadow length?

Control variables: fix object, screen distance, room darkness. Change only light source distance. Year 3 pupils plan steps, predict outcomes, measure thrice per setup, average results. Teacher modeling ensures repeats, building reliable data skills for curriculum standards.