1. Light, Reflection, and Color

2. What is Light? How do we see?

3. What is Light? Light as a Wave

4. What is Light? Light as a Particle

5. Light – Wave or Particle? Evidence for Light as a Wave Interference Light can produce interference patterns (a wave property). Light behaves like a transverse wave when it is diffracted (a wave property). Evidence for Light as a Particle The Photoelectric Effect Blue light produces electricity, but no amount of red light can. If light were waves, then a whole lot of red light should produce electricity. Light intensity (brightness) is best explained by light as a particle. So, what is light? Einstein’s Conclusion: Light is both a Wave and a Particle

6. What is Light? Electromagnetic Waves c = constant speed of light

7. The Speed of Light – Galileo

8. The Speed of Light – Olaus Römer

9. The Speed of Light – Fizeau

10. The Speed of Light – Michelson

11. The Speed of Light – Modern Methods

12. The Speed of Light To accurately and precisely measure the speed of light, you must be able to do one of two things: Measure light traveling vast distances Measure very short periods of time The current accepted value for the speed of light in a vacuum is: 299,792,458 m/s ~3.00 x 10 8 m/s ~186,000 miles/sec ~671 x 10 8 miles/hr

13. How Fast is the Speed of Light? Light is fast, but it is not infinitely fast. Light travels at a constant, finite speed of 186,000 mi/sec. A traveler, moving at the speed of light, would circumnavigate the equator approximately 7.5 times in one second. By comparison, a traveler in a jet aircraft, moving at a ground speed of 500 mph, would cross the continental U.S. once in 4 hours.

14. How Long is a Light-Year? The light-year is a measure of distance, not time. It is the total distance that a beam of light, moving in a straight line, travels in one year. To obtain an idea of the size of a light-year, take the circumference of the earth (24,900 miles), lay it out in a straight line, multiply the length of the line by 7.5 (the corresponding distance is one light- second), then place 31.6 million similar lines end to end. The resulting distance is almost 6 trillion (6,000,000,000,000) miles!

15. Light Year

16. The Electromagnetic Spectrum ↑F ↓ ↑E

17. Electromagnetic Spectrum

18. Radio Waves

19. Electromagnetic Spectrum NASA/Goddard Space Flight Center Scientific Visualization Studio Kashima Space Center, JapanJapan Dave Thompson (NASA/GSFC)GSFC National Oceanic and Atmospheric Administration (NOAA)

20. DiaFAST

21. Electromagnetic Spectrum

22. Sample Problem

23. Reflection of Light Reflection is the change in direction of an electromagnetic wave at a surface that causes it to move away from the surface.

31. Reflection of Light

32. Image Formation by a Flat Mirror

33. p = object distanceq = image distance h = object heighth' = image height

34. 50° 60° Ray Diagrams for Flat Mirrors 50° 60°

35. F Ray Diagrams – Curved Mirrors C object image Ray #1 Ray #2 RayLine drawn from object to mirrorLine drawn upon reflection 1Parallel to principal axisThrough the focal point, F 2 Parallel to principal axis 3Through the center of curvatureBack along itself through C Ray #3 p. 459

36. Ray Diagrams – Curved Mirrors Real, Inverted, │M│ < 1 Real, Inverted, │M│ = 1 CF CF 1. 2.

37. Ray Diagrams – Curved Mirrors Reflected rays are parallel. Image is Real, Inverted, and at ∞ (M is ∞). Real, Inverted, │M│ > 1 CF CF 3. 4. Ray #3

38. Ray Diagrams – Curved Mirrors Virtual, Upright, │M│ > 1 CF CF Virtual, Upright, │M│ < 1 5. 6. Ray #1 Ray #2 Ray #3 Ray #1 Ray #2 Ray #3

39. Mirror Equations See p. 464 for all sign conventions. p = object distanceq = image distance h = object heighth' = image height f = focal length

40. Sample A concave spherical mirror has a focal length of 10.0 cm. Locate the image of a pencil that is placed upright 30.0 cm from the mirror. Find the magnification of the image. Draw a ray diagram to confirm your answer.

41. Sample, cont. Draw a ray diagram using the rules for drawing reference rays (Use Diagram #2 on p. 460 as reference).

42. Sample An upright pencil is placed in front of a convex spherical mirror with a focal length of 8.00 cm. An upright image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.

43. Image Formation by a Convex Spherical Mirror

44. Spherical Aberration and Parabolic Mirrors

45. Color Vision

46. Test for Color Blindness

47. White

48. Red

49. Green

50. Blue

51. Yellow = Red + GreenYellow = White - ? Blue

52. Magenta = Red + BlueMagenta = White - ? Green

53. Cyan = Green + BlueCyan = White - ? Red

54. White = Red + Blue + Green

56. Color by Addition – Adding Light

57. Red Green Blue Yellow Cyan Magenta White

58. Color by Subtraction – Mixing Pigments W – R = CW – B = YW – G = M What happens when we mix pigments? Think about what is being subtracted from White light.

59. Color by Subtraction – Mixing Pigments

60. Red GreenBlue Yellow Cyan Magenta Black

61. Color

62. Retinal Fatigue

64. Linearly Polarized Light

65. Aligned and Crossed Polarizing Filters Crossed FiltersAligned Filters

66. Polarized Sky Light