This definitions covers Key Definitions within Reflection & Refraction for GCSE Physics. Revise Reflection & Refraction in Waves for GCSE Physics with 15 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 7 of 13 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 7 of 13
Practice
15 questions
Recall
15 flashcards
📖 Key Definitions
Normal: An imaginary line drawn perpendicular (at 90°) to a surface at the point where a ray meets it. All angles in optics are measured from the normal.
Angle of incidence: The angle between the incident (incoming) ray and the normal at the point of incidence.
Angle of reflection: The angle between the reflected ray and the normal. Always equals the angle of incidence.
Refraction: The change in direction of a wave as it passes from one medium to another, caused by a change in wave speed.
Critical angle: The angle of incidence (in the denser medium) at which the refracted ray travels along the boundary (angle of refraction = 90°). Beyond this, total internal reflection occurs.
Total internal reflection (TIR): Complete reflection of a wave at a boundary when the angle of incidence exceeds the critical angle, with no refraction into the less dense medium.