# Refraction

## Refraction

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##### Presentation Transcript

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

2. Index of Refraction

3. Index of Refraction

4. When light moves from a faster medium to a slower medium, it bends ….. Speed of light (m/s) n ∠i 1.00 3.00 x 108 vacuum 1.33 2.26 x 108 water ∠R

5. When light moves from a slower medium to a faster medium, it bends ….. when n2 is less than n1 ∠R n2 = 1.00 air n1 = 1.33 water ∠i ∠i is less than ∠R

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

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

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

9. Critical Angle the angle of incidence that produces a refracted angle of 90°. Only occurs when n1 is greater than n2 A physical property of the medium.

10. What happens when an incident angle is greater than the critical angle? ∠R air water ∠i Reflection occurs on the surface. critical angle Critical angle for water: 48.8° Total Internal Reflection

11. 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 n1 is greater than n2

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

13. Refraction in a diamond

14. Fibre Optics

15. Fibre Optics

17. The speed of communications

18. Fibre Optics – endoscope

19. Fibre Optics – endoscope

20. 45° 45° Triangular Prism

21. 45° 45° 45° 45° Triangular Prism

22. Triangular Prism

23. 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

24. Retro-reflectors and Prisms

25. Retro-reflectors and Prisms An optical device in which the emergent ray is parallel to the incident ray

26. Retro-reflectors and Prisms

27. Diagram of a Retro-reflector

28. Retro-reflectors and Prisms

29. Retro-reflectors – examples

30. Retro-reflectors – examples