1. { Refraction The bending or change in direction of light when it travels from one medium into another.

2. 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

3. Index of Refraction

4. ∠R∠R ∠i∠i water vacuum Speed of light (m/s) n 1.33 1.00 3.00 x 10 8 2.26 x 10 8 When light moves from a faster medium to a slower medium, it bends …..

5. ∠R∠R ∠i∠i 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 …..

6. What happens when you keep increasing the angle of incidence? water air ∠ i can be any angle

7. What happens when you keep increasing the angle of incidence? water air ∠ i can be any angle

8. Critical angle water air If ∠ R becomes 90° ∠ i must be less than 90° ∠R∠R ∠i∠i

9. { 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.

10. Total Internal Reflection water air ∠R∠R ∠i∠i 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°

12. { 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

15. Refraction in a diamond critical angle for diamond: 24.4°

16. Refraction in a diamond

17. Fibre Optics

19. Fibre Optic Cables www.youtube.com/watch?v=0MwMkBET_5I

21. The speed of communications

22. Fibre Optics – endoscope

24. Triangular Prism 45°

25. Triangular Prism 45°

26. Triangular Prism

27.  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

28. Retro-reflectors and Prisms

29. { An optical device in which the emergent ray is parallel to the incident ray

30. Retro-reflectors and Prisms

31. Diagram of a Retro-reflector

32. Retro-reflectors and Prisms

33. Retro-reflectors – examples