PhET Ray Lab

Overview

Students investigate wave behaviours of light by combining PhET simulations (Bending Light and Wave Interference) with short physical experiments using mirrors and lenses. They test, measure, and justify predictions about refraction (and wave interference where relevant) using ray diagrams and evidence from data.

Learning intentions

• Students will explain how waves of light bend when moving between different media (refraction) using measured angles.
• Students will use ray diagrams to represent reflection and refraction and compare their predictions with results from both virtual and physical setups.
• Students will interpret outcomes from wave interference to link pattern changes to wave behaviour.
• Students will communicate a scientific explanation using appropriate wave/light terminology and evidence.

Success criteria

• I can identify and describe reflection and refraction as wave behaviours of light and state that refraction involves a change in direction.
• I can measure incident and refracted angles (digitally or with a protractor) and record them clearly.
• I can draw ray diagrams (virtual and hand-drawn) that match the observed paths.
• I can write a short, evidence-based explanation of whether my refraction predictions were supported.

Curriculum links

• PY-11-02: Students explain the properties and behaviours of waves, including wave behaviours relevant to light.
• PY-11WS-06: Students use scientific process to solve scientific problems by questioning, predicting, planning/doing measurements, and processing/analysing results.
• PY-11WS-07: Students communicate scientific arguments using evidence, scientific language and terminology for a specific audience.
• (Context connection) This lesson supports the unit focus “Exploring the World of Waves” through light wave behaviours, using simulations and ray models.

Lesson structure (45 minutes)

1. 0–5 min · Hook (prediction challenge). Teacher shows a diagram: a ray passing from air into glass and asks, “What changes—speed, direction, or both? What will happen to the angle as it enters?” Students think-pair-share and write one prediction sentence.

2. 5–12 min · Mini teach (model + measurements). Teacher reviews ray terminology: incident ray, normal, reflected ray, refracted ray; how to define angles using the normal. Students watch teacher demonstrate how to measure angles and label a ray diagram correctly.

3. 12–22 min · Simulation rotation A (Bending Light). Teacher releases students in pairs to PhET “Bending Light”, setting up different materials and recording at least 3 trials per pair. Students measure incident and refracted angles using the simulation’s angle read-outs, then draw a quick ray diagram for each trial.

4. 22–30 min · Physical check (mirror + lens quick stations). Teacher groups pairs at two benches: one with a plane mirror (reflection) and one with a lens/transparent block setup (refraction). Students perform two short trials each: one for reflection (angle of incidence vs angle of reflection) and one for refraction (angle in air vs angle in the material), recording angles in the same format as the simulation table.

5. 30–37 min · Simulation rotation B (Wave Interference pattern). Teacher runs a brief prompt: “Change wavelength or path difference—how does the brightness/darkness pattern respond?” Students use PhET “Wave Interference” for 1–2 adjustments and record one observation that links to wave behaviour (constructive vs destructive outcomes).

6. 37–44 min · Data synthesis + written argument. Teacher provides an “evidence to conclusion” sentence frame on the board: “My prediction was… The evidence shows… This supports/refutes because…” Students choose the best two refraction trials (virtual or physical) and write a 6–8 sentence explanation that includes one labelled ray diagram and a comparison of predicted vs observed results.

7. 44–45 min · Exit ticket. Students submit one of the following: (a) a labelled ray diagram matching the last refraction result, or (b) one claim with one piece of measured evidence supporting it.

Resources

• Laptops/tablets with PhET installed or accessible offline
• “Bending Light” simulation and “Wave Interference” simulation (prepared to start at appropriate difficulty)
• Lab data sheets (incident angle, refracted angle, normal, notes) for each pair
• Plane mirror, protractors, markers/labels (tape), rulers
• Lens or transparent block/rectangular acrylic for refraction station
• Torch or laser pointer (where safe and allowed), plus paper screen or whiteboard surface
• Normal templates or printed angle-measure guides for accurate angle referencing
• Whiteboard/markers and projector for demo
• Timer and station signs

Assessment

• Formative during rotations: teacher checks that students correctly identify the normal and record incident/refraction angles with consistent headings.
• Formative during discussion: teacher listens for accurate use of “incident”, “reflected”, “refracted”, and claims tied to measurements rather than guesswork.
• Summative for the lesson: short scientific explanation (6–8 sentences) and one labelled ray diagram plus an exit ticket claim-evidence link.

Differentiation

• Support: provide a partially completed ray diagram template with the normal already drawn and sentence starters for the written explanation.
• Support: pre-teach how to label angles and ensure students use the same reference line (the normal) across simulation and physical work.
• Extension: ask students to look for systematic differences between virtual and physical results and suggest one factor that could cause error (e.g., measurement uncertainty, alignment, surface quality).
• EAL/SEN: allow diagram-first answers (students can earn marks with accurate labelled ray diagrams) and provide simplified terminology card: incident/reflected/refracted/normal/angle.

Extension (optional)

• Skip.