Exploring Colour and Light

Overview

This lesson will build on Year 8 students' previous learning about light as a wave and their practical experience with the dispersion of white light through a triangular prism. The focus will be on understanding colour in terms of light wavelengths and how this relates to perception and materials. Students will explore the science behind colour formation, reflection, and absorption, linking theory to real-world materials and technology.

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National Curriculum Links (England, KS3 Science)

• Physics - Light (Programme of Study)
  • Understand that light transfers energy from source to observer
  • Recognise that white light is a mixture of different colours which can be seen by dispersion
  • Explain how different colours correspond to different wavelengths of light
  • Describe how objects appear coloured due to reflection and absorption of particular wavelengths of light

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Learning Objectives

By the end of the 45-minute lesson, students will:

1. Explain how visible colour corresponds to different wavelengths of light (NC Physics 3a, 3c).
2. Describe how objects appear coloured due to selective reflection and absorption of wavelengths (NC Physics 3d).
3. Apply knowledge of light wavelengths to predict the apparent colour of objects under different light conditions.
4. Analyse and interpret observations from a practical activity linking colour perception to wave properties.

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Resources Needed

• White light source (e.g., torch)
• Colour filters (red, blue, green, yellow)
• Various coloured objects/material samples (e.g., red apple, green leaf, white paper, black cloth)
• Worksheets summarising wavelengths of visible light spectrum
• Prism (from previous lesson if available)
• Whiteboard or interactive display
• Stopwatches or timers

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Lesson Structure

1. Starter (5 minutes)

Engage with an enquiry question:

• Ask students: “Why do leaves look green?”
• Encourage quick pair discussion.
• Recap on dispersion of white light and how white light consists of different colours corresponding to wavelengths.

Teacher note: emphasise the concept of visible spectrum – link to previous prism practical.

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2. Introduction and Explanation (10 minutes)

Direct Teaching Points:

• Display the visible spectrum with wavelength ranges in nanometres (approx. 400 nm - violet to 700 nm - red).
• Explain how different colours correspond to different wavelengths of visible light.
• Introduce concept of selective reflection and absorption:
  • Objects appear coloured because they reflect certain wavelengths and absorb others.
  • For example, a green leaf absorbs all except green light which it reflects.
• Use diagrams on the board illustrating light hitting an object and being absorbed or reflected.

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3. Practical Activity (15 minutes)

“Investigating Colour Perception Using Filters and Objects”

• Students work in small groups (4 per group) around stations.
• Each station contains coloured filters, white light source, and a variety of coloured objects.
• Tasks for each group:
  1. Shine white light through different colour filters onto objects.
  2. Observe and record the apparent colour changes.
  3. Use reasoning about which wavelengths are absorbed or reflected by objects to explain the changes.

Expected outcomes:

• Objects appear differently under filters because only specific wavelengths pass through and are reflected.
• Black objects absorb most wavelengths; white objects reflect most wavelengths.

Teacher notes:

• Circulate and prompt groups to link what they see to wavelength theory.
• Use questioning like: “Why does the red apple appear black under the blue filter?”

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4. Discussion and Consolidation (8 minutes)

• Invite groups to share their findings and explanations.
• Guide whole-class discussion to clarify misconceptions.
• Link back to National Curriculum goals:
  • Emphasise how wavelengths relate to energy transfer from light source to observer.
  • Reaffirm the role of absorption and reflection in colour perception.

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5. Plenary – Quick Quiz & Reflection (5 minutes)

• Conduct a quick quiz on key points (e.g., What colour corresponds to around 650 nm wavelength? Why does an object appear red?).
• Ask students to write a short sentence explaining why a black object heats up more in sunlight than a white one.
• Collect responses for assessment.

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Assessment for Learning

• Formative assessment during practical through questioning and observation of group discussions.
• Plenary quiz provides immediate feedback on student understanding.
• Worksheet notes to check for completeness and comprehension.

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Differentiation & Inclusion

• Support worksheets with diagrams and keyword glossaries for learners needing visual aids.
• Challenge higher ability students to consider how lighting conditions (e.g., sunset vs midday) affect colour perception.
• Use group work to support peer learning.
• Make adaptations for students with visual impairments (e.g., using texture or electronic colour simulators if possible).

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Cross-curricular Links

• Art & Design: Understanding colour theory in light and pigment.
• Mathematics: Measuring wavelengths and calculating frequency from wave speed.
• Geography: Effects of light on plant leaves and photosynthesis.

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Extension Ideas (For Homework or Further Lessons)

• Investigate how colour vision varies in animals.
• Explore the use of coloured light in technology (e.g. LED screens, laser pointers).
• Model the dispersion of light using ray tracing software or apps.

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This lesson plan applies the National Curriculum’s focus on light waves, energy transfer, and colour perception for Year 8 students, using engaging practical work and structured opportunities for reflection and assessment. It encourages scientific reasoning grounded in wave theory and links directly to previous lessons and future learning.