Reflection Angle Evidence

Overview

In this third lesson of Light: Paths, Bends and Bounces, students explain evidence from Lessons 1–2 using precise scientific language. They model reflection with mirrors, torches and ray diagrams, then conduct a fair test to investigate whether the angle of incidence equals the angle of reflection.

Learning intentions

Students will:

• explain that light travels from a source in straight rays and can reflect from a surface
• identify and use the terms incident ray, reflected ray, normal, angle of incidence and angle of reflection
• plan and conduct a fair test by changing one variable and controlling others
• measure, record and compare angles, using evidence to explain a pattern

Success criteria

• I can draw or build a ray diagram with arrows showing the direction of light.
• I can correctly measure and classify angles using a protractor.
• I can describe reflection using the words incident ray, reflected ray and normal.
• I can compare my results with my prediction and use evidence to support a conclusion.

Curriculum links

• Science: sources of light, straight-line travel, shadows, reflection and refraction.
• Science inquiry: posing investigable questions, making predictions and conducting repeatable fair tests.
• Science representation and analysis: organising data in tables, identifying patterns and drawing reasoned conclusions.
• Mathematics: measuring and classifying angles, using degrees and interpreting measurement data.

Lesson structure (60 minutes)

1. 0–10 min · Revisit and model. Open with the introduction and vocabulary slides and display the question, “Which angle are we measuring?” Revisit station observations from Lessons 1–2: a torch is a source, light travels in a straight path, and a shadow forms when light is blocked. Demonstrate a torch, mirror and screen, keeping the beam directed below eye level. Draw the normal at 90° to the mirror and model arrows from source to mirror and mirror to screen. Students identify the source, incident ray, reflected ray and normal, then predict what will happen when the incoming angle changes.

2. 10–17 min · Clarify the evidence. Use the reflection explanation and worked ray diagram to show that the angle of incidence is measured between the incident ray and the normal, not the mirror surface. Explain that the angle of reflection is measured between the reflected ray and the normal. Students practise locating both angles on a projected diagram and classify examples as acute, right or obtuse.

3. 17–24 min · Plan a fair test. Display the investigation question and method steps: “How does changing the angle of incidence affect the angle of reflection?” In teams of four, students assign roles: equipment manager, torch operator, measurer and recorder. Together they identify the changed variable (angle of incidence), measured variable (angle of reflection) and controlled variables (same mirror, torch, surface, distance and measuring method). Students make a prediction and agree on at least three test angles. Briefly discuss risks: never shine torches into eyes, keep mirrors stable and walk carefully around equipment.

4. 24–43 min · Conduct and record. Distribute the reflection investigation worksheet and the Results Table Builder Cards to teams. Students use the cards to check that their table includes angle of incidence, angle of reflection, units and repeated trials where possible. They create a tabletop ray model using a mirror, torch and wool or string, or use projected light if available. For each chosen angle, they mark the incident and reflected paths, measure both angles from the normal with a protractor and record results in a table. The teacher circulates, checking that protractors are centred on the vertex and that students measure from the correct ray.

5. 43–50 min · Compare findings. Ask teams to compare their measured pairs and look for a relationship. Students add arrows and labels to a ray diagram on the worksheet, then discuss: “What relationship do the two angles show?” Teams compare one result with another team’s method and data, identifying possible error such as a thick ray, a moving mirror, an off-centre protractor or inaccurate torch positioning.

6. 50–60 min · Gallery walk and CER. Open the gallery-walk prompts and conclusion slide. Teams display their ray model, diagram and table. During a brief gallery walk, students leave one verbal or written observation about another team’s evidence. Individually, students complete a short claim-evidence-reasoning response: claim whether the two angles were equal or close; evidence from at least two measured results; reasoning explaining that reflection changes the path of light while following a consistent relationship. Invite two students to share, then collect worksheets.

Resources

• the Light: Paths, Bends and Bounces teaching deck
• the reflection investigation worksheet
• the Results Table Builder Cards
• Small mirrors, one per team
• Torches or a projected light source
• Wool, string, masking tape and white paper
• Protractors, rulers and pencils
• Safety glasses if available

Assessment

• Observe whether students identify the normal and measure both angles from the normal, not the mirror surface.
• Check the fair-test plan, measured-data table, labelled ray model and correct use of vocabulary.
• Use the written or oral CER response to assess whether students select data as evidence and explain the observed relationship.

Differentiation

• Support learners with pre-drawn axes and normals, colour-coded incident and reflected rays, large protractors, a worked example and physical demonstrations of angles. Provide sentence starters: “My claim is…”, “My evidence is…” and “This supports my claim because…”.
• Provide symbol-supported vocabulary, uncluttered diagrams, enlarged worksheet text, audio instructions or a short recorded explanation. Allow oral rehearsal, collaborative recording, drawing instead of extended writing and speech-to-text.
• Pair students strategically and provide clearly assigned roles. Recheck understanding individually before students begin measuring.
• Extension students test whether the pattern holds with a different mirror or another smooth surface, repeat trials and evaluate which measurement errors most affected their conclusion.