IGCSE›Edexcel IGCSE Physics›Mind mapsReflection & RefractionEdexcel IGCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsReflectionLight is a transverse waveAngle of incidence = angle of reflectionMeasure angles from the normalNormal is at 90° to the surfaceRefractionChange of direction and speed at a boundaryLight is slower in denser mediaEntering denser: bends towards the normalLeaving denser: bends away from the normalRefractive indexn=sinisinrn = \frac{\sin i}{\sin r}n=sinrsiniHigher nnn: bends and slows light more40° in, 25° out gives n≈1.52n \approx \mathbf{1.52}n≈1.52Light bendingreflection, refractionnnniiirrrcccTotal internalDenser to less dense medium onlyAngle of incidence above the critical angleAt ccc the refracted ray runs along the boundarysinc=1n\sin c = \frac{1}{n}sinc=n1TIR usesOptical fibres carry light with little lossPrisms turn light through 90° or 180°Used in periscopes and binocularsExam tipsState angles are from the normalTIR needs both conditionsGlass block: ray emerges parallel to the original