{ Refraction The bending or change in direction of light when it travels from one medium into another. Index of Refraction Mediumn Vacuum/space and Air1.00 Ice1.31 Water (pure)1.33 Ethyl alcohol1.36 Quartz1.46 Vegetable oil1.47 Olive oil1.48 Acrylic1.49 Glass1.52 Diamond2.42 Index of Refraction RR ii water vacuum Speed of light (m/s) n x x 10 8 When light moves from a faster medium to a slower medium, it bends .. RR ii water air n 1 = 1.33 n 2 = 1.00 when n 2 is less than n 1 i is less than R When light moves from a slower medium to a faster medium, it bends .. What happens when you keep increasing the angle of incidence? water air i can be any angle What happens when you keep increasing the angle of incidence? water air i can be any angle Critical angle water air If R becomes 90 i must be less than 90 RR ii { Critical Angle the angle of incidence that produces a refracted angle of 90. Only occurs when n 1 is greater than n 2 A physical property of the medium. Total Internal Reflection water air RR ii What happens when an incident angle is greater than the critical angle? critical angle Reflection occurs on the surface. Critical angle for water: 48.8 { Total Internal Reflection When the angle of incidence is greater than the critical angle, light is reflected at the surface of the medium. Note: only occurs when n 1 is greater than n 2 Refraction in a diamond critical angle for diamond: 24.4 Refraction in a diamond Fibre Optics Fibre Optic Cables The speed of communications Fibre Optics endoscope Triangular Prism 45 Triangular Prism 45 Triangular Prism Plane Mirrors vs. Triangular Prisms: In triangular prisms almost 100% of light is reflected. Mirrors absorb some light, reducing quality. More durable. Opaque surfaces in mirrors often deteriorate over time. Triangular Prism Retro-reflectors and Prisms { An optical device in which the emergent ray is parallel to the incident ray Retro-reflectors and Prisms Diagram of a Retro-reflector Retro-reflectors and Prisms Retro-reflectors examples