Reflection and Refraction of Waves

This lesson covers the reflection and refraction of waves — two key behaviours that all waves exhibit — as required by AQA GCSE Combined Science Trilogy (8464), Physics Paper 2, section 6.1. You need to understand what happens when waves meet a boundary and be able to draw accurate ray diagrams.

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Reflection

Reflection occurs when a wave bounces off a boundary (a surface) and changes direction.

The Law of Reflection

$\text{angle of incidence} = \text{angle of reflection}$angle of incidence=angle of reflection

$\theta_i = \theta_r$θi​=θr​

graph TD
    N["Normal (perpendicular to surface)"]
    I["Incident ray"] -->|"θi"| P["Point of incidence on surface"]
    P -->|"θr"| R["Reflected ray"]

    style N fill:#7f8c8d,color:#fff
    style I fill:#2980b9,color:#fff
    style P fill:#2c3e50,color:#fff
    style R fill:#e74c3c,color:#fff

Key Definitions

• Normal — an imaginary line drawn at right angles (90°) to the surface at the point where the ray hits.
• Angle of incidence (θi) — the angle between the incident ray and the normal.
• Angle of reflection (θr) — the angle between the reflected ray and the normal.