2.3 Reflection, Refraction and Total Internal Reflection
Ray diagrams, normal lines, reflection law, refraction by speed change, refractive effects, critical angle and total internal reflection.
How to study for CCEA GCSE Physics
Link every equation to a physical model and unit, interpret graphs and evidence, and prepare each prescribed practical from method through evaluation.
Core concepts
Concept 1
Angles of incidence, reflection and refraction are measured from the normal, not from the surface.
Exam cue: Confirm the CCEA unit, tier and whether the task tests a model, calculation, explanation or practical judgement.
Concept 2
Refraction occurs when light changes speed at a boundary and changes direction unless it travels along the normal.
Exam cue: Draw a normal, add directional arrows, measure every angle from it and state both total-internal-reflection conditions.
Concept 3
Total internal reflection requires travel from an optically denser medium and incidence beyond the critical angle.
Exam cue: Show substitutions and units, connect evidence to the physical model and limit the conclusion to the stated conditions.
Risk pitfalls and guardrails
Measuring from the boundary surface or claiming every ray entering glass bends towards the normal regardless of direction.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a causal physical explanation with an equation alone.
Importing an equation sheet, Higher-only boundary or paper convention from an England 9-1 board.
Guardrail: Use the current CCEA formatting to confirm Higher-only content and the correct paper duration; do not infer tier scope from another exam board.
Giving a calculator display or named law without the working, units, causal explanation or evidence the command word requires.
Guardrail: Do not import an England board, Single Award or Double Award structure, and do not replace a causal physical explanation with an equation alone.
Memory anchors
Normal
A line perpendicular to a surface at the point where a ray meets it.
Angle of incidence
Angle between the incident ray and the normal.
Angle of reflection
Angle between the reflected ray and the normal.
Refraction
Change in wave direction caused by a change in speed at a boundary.
Critical angle
Incident angle in the denser medium that produces a refracted ray along the boundary.
Total internal reflection
Complete reflection inside a denser medium beyond the critical angle.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
An incident light ray makes 35° with the normal of a plane mirror. What is the angle of reflection?
A ray makes 20° with a mirror surface. What is its angle of incidence?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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