1. Reflection & Refraction
Chapter 17
Reflection & Refraction

2. When light rays bounce back off of a medium boundary
Reflection
When light rays bounce back off of a medium boundary

3. The bending of light rays when passing from one medium to another
Refraction
The bending of light rays when passing from one medium to another

4. A straight line path representing the direction of a light wave
Ray
A straight line path representing the direction of a light wave

5. Specular Reflection
Reflection off of a smooth surface which results in reflected wave that are parallel

6. Mirrors give regular reflections
Specular Reflection
Produce good images
Mirrors give regular reflections

7. Diffuse Reflection
Reflection off of a rough surface which results in reflected waves that are not parallel

8. Diffuse Reflection
Because light waves are scattered all over the place, no image can be seen

9. The angle of reflection equals the angle of incidence
Law of Reflection
The angle of reflection equals the angle of incidence

10. Law of Reflection
 b =  a a
Normal  b

11. Optical Density
How fast light passes through a substance as compared to the speed of light in a vacuum.

12. Optical Density
As optical density increases, the speed in which light passes decreases

13. Index of Refraction (n)
Ratio of the speed of light in a vacuum to the speed of light in a material

14. Indices of Refraction Vacuum: n = 1.00 Air: n = 1.0003 Water: n = 1.33
Ethanol: n = 1.36

15. Indices of Refraction Crown glass: n = 1.52 Quartz: n = 1.54
Flint glass: n = 1.61
Diamond: n = 2.42

16. Speed of Light in Other Substances
vsub
nsub =

17. Speed of Light in Other Substances
nsub
vsub =

18. Solve for the speed of light in each of the following: water (n = 1
Solve for the speed of light in each of the following: water (n = 1.33) crown glass (n = 1.52) diamond (n = 2.42)

19. Solve for the speed of light in a substance with an optical density of 1.50:

20. Snell’s Law
The ratio of the sine of the angle of incidence over the sine of the angle of refraction is constant for any substance

21. Snell’s Law
sin ai
sin ar
n =

22. Snell’s Law
ni sin ai = nr sin ar

23. Snell’s Law ar ai
n2 = water
n1 = air

24. Draw a model with a light ray passing from one medium to another more optically dense medium. Include reflection & refraction

25. A light ray from air
(nair = 1.00) strikes glass (nglass = 1.52) with an incident angle of 30.0o. Calculate the angle of refraction:

26. A light ray from air
(nair = 1.00) strikes glass (nglass = 1.61) with an incident angle of 36.9o. Calculate the angle of refraction:

27. A light ray from air
(nair = 1.00) & strikes diamond (ndiamd = 2.42) with an incident angle of 45.0o. Calculate the angle of refraction:

28. A light ray incident from air (nair = 1. 00) at 45
A light ray incident from air (nair = 1.00) at 45.0o passes into an unknown substance at 30.0o. Calculate its index of refraction:

29. Total Internal Reflection
When light passes from a more optically dense substance to a less optically dense one, the angle of refraction > the angle of incident

30. b a

31. Total Internal Reflection (TIR)
When the angle of refraction  90o, total internal reflection occurs.

32. Calculate the angles where TIR occurs when light passes from the following to air: water (n = 1.33) crown glass (n = 1.52) diamond (n = 2.42)

33. Applications & Effects
Prisms
Fiber Optics
Mirages
Red Sunsets
Rainbows

34. Prisms
When light pass through a prism the various wavelengths of light are dispersed or separated into a spectrum

35. Prisms

36. Fiber Optics
A light wave can pass through a thin glass thread surrounded by a reflective substance. Even if the glass thread is bent, the wave passes through as it reflects off the sides.

37. Mirages
Light refracted from a far away source looks closer

38. Mirages

39. Sunsets & Rises
Sunlight is refracted as it strikes the atmosphere at great angles bending light towards Earth

40. Sunsets
Because different wavelengths are refracted differently, colors change

41. Sunsets

42. Rainbows
Sunlight is refracted & reflected by rain droplets dispersing the light into a spectrum

43. Rainbows

44. Rainbows
Rainbows fall
from 40 – 42o
from incident

45. Rainbows
Rainbows fall
from 40 – 42o
from incident

46. A light ray from water
(nw = 1.33) & strikes diamond (ndiamd = 2.42) with an incident angle of 53.0o. Calculate the angle of refraction:

47. A light ray from water
(nw = 1.33) & strikes glass (nglass = 1.51) with an incident angle of 53.0o. Calculate the angle of refraction:

48. Calculate the angle of total internal reflection of pukon with n = 3

49. Calculate: refl & refr
An incident ray from air strikes quartz (n = 1.50) at an angle of 30o from normal.
Calculate: refl & refr