1. The Nature and Propagation of Light
Chapter 33
The Nature and Propagation of Light

2. Reflection and Refraction

3. Reflection

4. Reflection
We will focus on specular reflection

5. The Law of Reflection
All angles are measured with respect to the normal.
normal

6. Multiple reflections

7. The image

8. Where is the image? Trace at least two light rays.
The image is at where the rays meet.
Bring a protractor to class and quizzes and exams.

9. Where is the image? Trace at least two light rays.
The image is at where the rays meet.

10. Finding the image

11. Image with multiple reflections

12. Snell’s Law of Refraction

13. Refractive Index

14. Useful facts

15. Reflection and refraction

16. Be careful with the normal

17. More on refractive index

18. Find the refractive index and the speed of light in the liquid

19. Solution

20. Different colors different speed

21. Dispersion

22. What happened to my ruler?

23. Explanation

24. How to catch a fish

25. How to catch a fish

26. The image

27. How to catch a bug

28. Find θair for the following cases:
θwater
θair
40°
47°
48°
48.75°
50°
nwater = 1.33

29. Solution θwater θair 40° 58.7° 47° 76.6° 48° 81.3° 48.75° 89.4° 50°
[Error]
Total internal reflection

30. Total Internal Reflection

31. A slightly more accurate picture

32. Total internal reflection (TIR)
Total internal reflection occurs when θincident > θc. It is when all the refracted light disappear and all the light got reflected back.

33. The critical angle, θc
θc is the angle of incident θincident when θrefraction = 90o

34. Wrong Answers! Define critical angle:
Critical angle is when TIR happens. (Is what???)
Critical angle is the angle of incidence when TIR happens. (TIR happens for many values of θincidence)
Critical angle is the angle when TIR begins. (Which angle???)
Define TIR:
TIR is when the the angle of incidence = critical angle. (What about θincidence>θc?)
TIR is when the the angle of incidence > critical angle. (Circular logic)

35. Find the critical angle for diamond in air

36. Shiny diamonds and total internal reflection

37. Cubic Zirconium Refractive index: 2.15 to 2.18 (diamond: 2.42)
Hardness: 8.5 to 9 (diamond: 10)
Ingredients: zirconium oxide, magnesium, calcium
(diamond: carbon)

38. Applications of TIR
Fiberoptics

39. Total internal reflection

40. Polarization

41. Polarizing Filters
Electrons on long polymers (long molecules) that moves only in one direction, hence absorbing energy of the E field in that direction, but let the other direction through.

42. Two filters

43. Intensity Rules for Polarizer
Make sure you know whether the light is polarized or unpolarized!

44. Example with two filters

45. Polarization by Reflection
At the Brewster angle (or polarizing angle) θp, the reflected beam becomes polarized.

46. Brewster’s Angle
Complete polarization by reflection occurs when the reflected beam is perpendicular to the refracted beam.

47. Brewster’s Angle
Pictures taken with polarizers at different angles. The picture on the right has the reflected light removed by the polarizer to minimize reflection.

48. Polarization by Scattering

49. Circular and Elliptical Polarization

50. Circular Polarization

51. Wavelength in different medium

52. Huygen’s Principle
Every point of a wave front may be considered the source of secondary wavelets that spread out in all directions with a speed equal to the speed of wave. The final wave is the sum of all these secondary wavelets.

53. Deriving Snell’s Law of Refraction

54. Principle of Least Time
Light always travels between two points in the path that takes the least amount of time.