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

Light and Colour

Students will explore how white light is made up of different colours and how objects appear to be different colours.

• National Curriculum Attainment Targets
• KS2: Science - Light

About This Topic

The light and colour topic shows that white light splits into a spectrum of colours. Year 3 students use prisms to separate sunlight or torchlight into red, orange, yellow, green, blue, indigo, and violet, much like rainbows form from refraction and reflection in raindrops. They test how objects appear under coloured filters, learning that objects reflect certain wavelengths while absorbing others, so a green leaf looks black under red light.

This topic anchors the Light and Shadows unit by building on light's straight-line travel and shadow formation. It aligns with KS2 standards on light properties and prepares students for optics in later years. Key skills include observing patterns, predicting results from fair tests, and explaining phenomena like rainbows using simple models.

Hands-on methods suit this topic perfectly since light effects are immediate and visual. When students shine torches through filters onto objects or create rainbows on walls, they gain concrete evidence that challenges prior ideas and sparks curiosity about everyday sights like traffic lights or sunsets.

Key Questions

1. Explain why a rainbow appears after rain.
2. Differentiate between primary and secondary colours of light.
3. Predict what colour an object would appear under different coloured lights.

Learning Objectives

• Demonstrate how white light can be separated into a spectrum of colours using a prism.
• Explain that objects appear a certain colour because they reflect specific wavelengths of light and absorb others.
• Predict the apparent colour of an object when viewed under different coloured lights.
• Classify colours as primary or secondary based on how they combine.

Before You Start

Properties of Light

Why: Students need to know that light travels in straight lines and can be blocked to form shadows before exploring how light interacts with objects and prisms.

Materials and their Properties

Why: Understanding that different materials interact with light differently, such as transparent, translucent, and opaque, provides a foundation for exploring reflection and absorption.

Key Vocabulary

spectrum	The range of colours that make up white light, visible when light is split, like in a rainbow.
refraction	The bending of light as it passes from one substance to another, such as from air into a prism or raindrop.
reflection	The bouncing of light off a surface. The colour we see is the light that is reflected.
absorption	The process where light energy is taken in by an object, rather than being reflected or transmitted.
primary colours of light	The basic colours of light (red, green, and blue) that can be mixed together to create other colours.
secondary colours of light	Colours made by mixing two primary colours of light, such as cyan (blue + green), magenta (blue + red), and yellow (red + green).

Watch Out for These Misconceptions

Common Misconception

Objects contain their colour inside.

What to Teach Instead

Objects reflect specific light colours and absorb others. Hands-on filter tests let students see a red sock vanish under green light, building evidence-based understanding through repeated trials and peer explanations.

Common Misconception

Rainbows form from sunlight mixing colours.

What to Teach Instead

Rainbows result from white light dispersing in water droplets. Prism activities mimic this process, allowing students to replicate and sequence refraction steps collaboratively.

Common Misconception

All coloured lights mix like paints.

What to Teach Instead

Light colours add, unlike subtractive paint mixing. Filter overlaps in group experiments show white from red and green, helping students distinguish light from pigment models.

Active Learning Ideas

Stations Rotation: Prism Rainbows

Prepare stations with prisms, torches, and white paper. Students shine light through prisms to project spectra, measure band widths, and note colour order. Rotate groups every 10 minutes, then discuss patterns as a class.

45 min·Small Groups

Pairs Investigation: Coloured Shadows

Provide torches, cellophane filters in red, blue, green, and white objects like toys. Pairs predict and test shadow colours on walls, record results in tables. Share findings to identify rules.

30 min·Pairs

Whole Class: Filter Prediction Challenge

Display objects under a projector with coloured filters. Class predicts appearances before revealing, votes on answers, then tests with handheld torches. Chart predictions versus observations.

25 min·Whole Class

Individual: Rainbow Journal

Students draw observed rainbows from prisms, label colours, and write explanations of raindrop roles. Include photos or sketches from outdoor hunts after rain.

20 min·Individual

Real-World Connections

• Lighting designers for theatres and concerts use primary and secondary colours of light to create specific moods and visual effects on stage.
• Traffic light systems rely on the principles of colour and light, using specific colours like red, amber, and green to convey important safety information.
• Artists and designers use colour theory, understanding how pigments absorb and reflect light, to choose colours for paintings, clothing, and product design.

Assessment Ideas

Exit Ticket

Provide students with a small prism and a torch. Ask them to draw what they observe when shining the light through the prism onto a white surface and label at least three colours they see in the spectrum.

Quick Check

Show students a red object and ask: 'If I shine a blue light on this red object, what colour will it appear? Explain your answer.' Listen for explanations involving reflection and absorption of light wavelengths.

Discussion Prompt

Pose the question: 'Why do we see a green leaf as green, but it looks black under a red light?' Facilitate a class discussion where students use terms like reflection and absorption to explain their reasoning.

Frequently Asked Questions

How do I explain rainbows to Year 3 students?

Use prisms to show white light splitting into colours, then model raindrops with glass beads or water sprays under torches. Explain refraction bends light, separates colours, and reflection sends it back. Simple diagrams and videos reinforce this during plenary discussions.

What activities work best for light and colour in Year 3?

Prism stations, coloured filter shadows, and prediction challenges engage students fully. These build observation skills and link theory to practice. Rotate setups to keep energy high and accommodate different needs.

How can active learning help students grasp light and colour?

Active approaches like manipulating torches and filters provide instant feedback, making abstract dispersion and reflection visible. Students predict, test, and revise ideas in pairs or groups, deepening retention over passive lectures. Collaborative data sharing reveals patterns, such as filter rules, fostering scientific discourse.

How to address why objects change colour under lights?

Demonstrate with torches and cellophane: shine red light on blue paper, it appears black as blue wavelengths are absent. Students test multiple combinations, tabulate results, and generalise that we see reflected light only. This predicts real-world examples like stage lighting.