Dispersion and Colour

National Curriculum Links

Science key stage 2:

• Light: Recognise that light appears to travel in straight lines (NC PoS 6a)
• Working scientifically: Plan and carry out fair tests; make systematic and careful observations (NC PoS Working Scientifically - years 5 & 6)

Specific Learning Objectives:
By the end of the lesson, pupils will:

• Understand that white light is made up of a spectrum of colours (NC PoS: light is made up of colours).
• Be able to explain the concept of dispersion and why light splits into different colours when passing through a prism.
• Describe real-life examples of dispersion, such as rainbows.
• Develop skills in making careful observations and recording results from a simple experiment involving prisms.

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Lesson Details

Year group: 6
Duration: 60 minutes
Class size: 30 students

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Resources Needed

• Triangular glass prisms (one per group of 4-5 pupils)
• White light source (small torch or strong flashlight)
• Large white card or paper (for projecting spectrum)
• Water spray bottle or access to water hose/outside area (for rainbow demonstration)
• Whiteboard and markers
• Colour printed spectrum chart
• Lined notebooks or science journals
• Projector or interactive whiteboard with images/videos of rainbows and prisms
• Worksheet for note-taking and reflection

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Lesson Structure

1. Starter Activity (10 minutes)

Engage curiosity with a question:

• Display an image of a rainbow and ask: "Have you ever wondered how a rainbow is formed? Why do we see so many colours in the sky after rain?"

Discussion:

• Brief whole-class discussion to gather prior knowledge.
• Introduce key vocabulary: dispersion, spectrum, prism, refraction.

Show a short animation or video (1-2 minutes) illustrating how white light splits into colours (without going into complex detail yet).

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2. Explain Concept (15 minutes)

Teacher-led explanation using visual aids:

• Explain that white light is not just one colour but a mix of many colours.
• Demonstrate how light travels in straight lines by shining a torch beam.
• Introduce the prism and explain deflection (refraction) and dispersion: how the prism bends light at different angles depending on the colour's wavelength, causing it to separate.

Interactive questionathon:

• Ask pupils to predict what will happen when the light passes through the prism.

Show a printed or projected spectrum (ROYGBIV colours) and link these to the colours seen when light disperses.

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3. Practical Activity – Dispersion Experiment (20 minutes)

Group Work: (Groups of 4-5)

• Pupils will use a torch, prism, and white card to project the spectrum of dispersed light.
• Encourage pupils to carefully observe and record:
  • What colours appear?
  • Order of colours.
  • How changing angle or distance affects dispersion.

Teacher Guidance:

• Circulate to support safe handling of prisms and torches.
• Ask probing questions: "Why do you think the colours are spreading out like this?"
• Encourage making labelled sketches in science journals.

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4. Real-Life Application and Discussion (10 minutes)

Whole-class share:

• Groups present findings briefly.
• Teacher shows how rain creates natural prisms in the form of water droplets, causing dispersion and rainbows.
• Discuss the role of sunlight and raindrops in forming a rainbow. Use a water spray in sunlight outside if weather permits.

Critical Thinking:

• Ask: "Why don’t we see rainbows all the time?"
• Discuss angle of the sun and observer’s location.

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5. Plenary and Assessment (5 minutes)

Quick Quiz / Exit Ticket:

• Pupils answer these in their notebooks:
  1. What is dispersion?
  2. Name the colours you see when white light splits?
  3. Give an example of dispersion found in nature.
  4. Why does white light split when it passes through a prism?

Teacher Review:

• Collect answers to assess understanding.
• Provide verbal feedback and clarify any misconceptions before ending.

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Extension / Homework Idea

• Create a poster or digital presentation explaining dispersion and rainbows, including labelled diagrams and key facts.

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Differentiation

• Support: Provide labelled diagrams and sentence starters for recording observations.
• Challenge: Pupils can investigate how prisms made of different materials affect dispersion or research the order of colours in a rainbow scientifically.

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Cross-curricular Links

• Art: Exploring colours and light in painting/colour mixing.
• Literacy: Using precise scientific vocabulary in explanations and descriptions.

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Reflections for Teachers

• Observe student engagement during practical tasks to gauge enthusiasm and understanding.
• Adapt questioning for groups struggling with abstract concepts about light and colour.
• Use formative assessment data from plenary to plan any needed follow-up lessons on light and optics.

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This lesson plan confidently grounds your teaching in the National Curriculum's science requirements for Year 6 while offering interactive, memorable experiences thatbring the science of light vividly to life.