1. If you can’t see him, he can’t see you! Warm up #1 Write the knowns and solve: The wavelength of an electromagnetic wave measures 3.63 x 10 -10 m. What is the frequency of this wave? 4/16 Pick up Light Notes II

2. Warm Up #1:The wavelength of an electromagnetic wave measures 3.63 x 10 -10 m. What is the frequency of this waveform? Is it an infrared wave? Explain. f = (3.00 x 10 8 m/s) / (3.63 x 10 -10 m) f = 8.26 x 10 17 Hz

3. TODAY IS LAST DAY FOR MAKEUPS Warm up #2 True or False? Gamma rays have the highest energy in the EM spectrum because they travel the fastest. 4/17 Yesterday we started Light Notes II. Get them out now. No calculators today ↑ What kind of image?

4. Polarized Sunglasses- How do they work? light waves vibrate in more than one plane light waves can be made to vibrate in a single plane by use of polarizing filters. 4

5. polarizing magic 5

6. What are the primary colors of light? How do you see color 6

7. Click on this hyperlinked address to access a terrific interactive website doing the above or use a set of flashlights. http://micro.magnet.fsu.edu/primer/java/primarycolors/addit iveprimaries/index.html

8. Eye anatomy Biologix: The eye Vision and Perception Eye anatomy Biologix: The eye Vision and Perception (29min)

9. What we see: In visible spectrum 400-700nm If you see red, object absorbs all frequencies of visible light but red, ie object reflects red White: combination of all visible light frequencies, all frequencies reflected Black: combination of all visible light frequencies absorbed, no frequencies reflected

10. Speed of Light The speed of all EM Waves (light) or “c” is 3 x 10 8 m/s. What is a light year? The distance light travels in one year Does light ever go slower? Yes, 3 x 10 8 m/s is the maximum and occurs in an vacuum. Light slows as it enters more dense medium. When it changes medium, it bends. What is this called? REFRACTION

11. Reflection and Refraction at an Interface Why does the light bend?

12. FYI: The speed of light c in a material is generally less than the free-space velocity c of 3 x10 8 m/s. In water light travels about three-fourths of its velocity in air. Light travels about two-thirds as fast in glass. index of refraction, n The ratio of the velocity c of light in a vacuum to the velocity v of light in a particular medium is called the index of refraction, n for that material.

13. Mirages 13

14. Rainbows Interesting tidbit: Sun is behind you for you to see a rainbow 14

15. Rainbows are due to refraction and reflection in water droplets 15

16. Key Terms 1.Object 2.Image 3.Real 4.Virtual 5.Plane 6.Convex 7.Concave 8.Converge 9.Diverge 10.Center of Curvature 11.Focal Length/Focal Point 16

17. 17 Reflection and Mirrors

18. REFLECTION OF LIGHT Light obeys the law of refection that states that: "The angle of incidence is equal to the angle of reflection."

19. Angle of Reflection = Angle of Incidence Angles are measured with respect to the normal line

20. If all surfaces reflect, why can’t I see my image?

21. Light reflection from a smooth surface is called regular or specular reflection. Light reflection from a rough or irregular surface is called diffuse reflection.

22. What type of reflection?

24. Fiber Optics is also an example of reflection TOTAL INTERNAL REFLECTION

26. Total Internal Reflection!!!

31. Embedded in counters and other surfaces

33. F. O. Glove: Replace your flashlight!

34. Wallpaper

35. Mirrors

36. When we look at something in the mirror, the light wave we see is the reflected ray:

37. 37 Object: source of rays Image: reproduction of object

38. 38 Describing Images Size –Same –Reduced –Enlarged Orientation –Upright or inverted, Reversed Virtual or Real

39. 39 Virtual reflected rays do not actually converge to form image. Cannot be projected. images form where light rays appear to have crossed. In mirrors, they form behind the mirror. are always upright.

40. 40 Real images form where light rays actually cross. Can be projected. In mirrors, they form on the same side of the mirror as the object since light can not pass through a mirror. are always inverted (flipped upside down).

41. Mirages 41

42. Rainbows Interesting tidbit: Sun is behind you for you to see a rainbow 42

43. Rainbows are due to refraction and reflection in water droplets 43

44. 44 Types of Mirrors Flat or Plane Convex Concave

45. FLAT MIRRORS A flat mirror reflects light rays in the same order as they approach it. Flat mirrors are made from pieces of plate glass that have been coated on the back with a reflecting material like silver or aluminum. The image is the same size as the object and the same distance behind the mirror as the object is in front of the mirror.

46. These images which appear to the eye to be formed by rays of light but which in truth do not exist are called virtual images. On the other hand real images are formed when rays of light actually intersect at a single point. Notice that the images formed by a flat mirror are, in truth, reflections of real objects. The images themselves are not real because no light passes through them.

47. Left-Right Reversal Why? Mirrors actually reverse you front to back, it is like turning a glove inside out

48. 48 Plane Mirrors: flat surface. ex. mirror hanging on the wall in your bathroom

49. Plane mirror ray diagram

50. 50 Plane Mirror In a plane mirror the object is the same size, upright, and the same distance behind the mirror as the object is in front of the mirror. Your mind extends the reflected ray beyond the mirror to form image.

51. 51 Think about your image in a plane mirror? What is the same? What is different?

52. 52 Images in a plane mirror are also reversed left to right.

53. 53 What type of image is shown above? –A. Real –B. Virtual Original image

54. 54 Concave mirrors: sphere whose inner surface was reflective Concave mirrors: aka converging mirrors since they bring light rays to a focus. ex. magnifying mirrors Convex mirrors: sphere whose outer surface was reflective. Convex mirrors: aka diverging mirrors since spread out light rays. ex store security mirrors Types of Mirrors Convex Concave

57. Convex Mirrors

58. 58 What type of mirror created this image? A.Plane B.Convex C.Concave OriginalImage

59. 59 What kind of mirror would be used to focus a beam of light? Concave

60. 60 Drawing Diagrams F: Focal Point, point where parallel light rays converge or appear to diverge. The focal point (F) is located halfway between the mirror’s surface and the center of curvature. f: focal length, distance between F and mirror/lens C: Center of curvature, geometric center of sphere of radius. C = 2f =radius Principle axis: line that passes through both the center of curvature (C) and the focal point (F) and intersects the mirror at a right angle.

61. 61 FC Principle Axis Concave Mirrors Light source Convex Mirrors FC Principle Axis Light source

62. 62 C=2f f = ? C/2

63. 63 A concave mirror has a radius of curvature of 15 cm. What is the focal length of this mirror? A. 15 cm B. 30 cm C. 7.5 cm

64. 64

65. 65 1. Start at top of object. Light ray 1 travels parallel to the principle axis, strikes the mirror, and is reflected back through the focal point (F). 2. Light ray 2 travels from top of object and strikes the mirror, is in line with the focal point. It is reflected back parallel to the principle axis. 3. Where these 2 reflected light rays intersect is the location of the image. Sometimes it is necessary to extend reflected rays beyond mirror. If above axis, erect; if below, inverted. Ray Diagram Rules

66. 66 Hints Images in front of mirror are always real Real Images are always inverted Inverted images are always below the principle axis If reflected rays do not cross, extend them behind mirror Images behind mirror are always virtual Virtual Images are always erect Erect images are always above the principle axis

67. 67 Object Location Real or Virtual Erect or Inverted Size Plane Mirror Concave Mirror Convex Mirror

68. 68 Locating images in concave mirrors Fill in hypertextbook.com

69. 69 Describe image when Object located beyond C Real or Virtual? Real Erect or Inverted? Inverted Same size, Enlarged or Reduced? Reduced Location? Between f and C Concave Mirror

70. 70 Concave Mirror with the Object located beyond C

71. 71 Light rays that travel parallel to the principle axis, strike the mirror, and are reflected back through the focal point (f). Concave Mirror Object beyond C

72. 72 Light rays that travel through the focal point (f), strike the mirror, and are reflected back parallel to the principle axis. Concave Mirror Object beyond C

73. 73 Concave Mirror Object beyond C Image: Real Inverted Smaller Between f and C The image is located where the reflected light rays intersect

74. 74 Concave Mirror with the Object located at C

75. 75 Concave Mirror Object at C Light rays that travel parallel to the principle axis, strike the mirror, and are reflected back through the focal point (f).

76. 76 Concave Mirror Object at C Light rays that travel through the focal point (f), strike the mirror, and are reflected back parallel to the principle axis.

77. 77 Concave Mirror Object at C Image: Real Inverted Same Size At C The image is located where the reflected light rays intersect

78. 78 Concave Mirror with the Object located between f and C

79. 79 Describe image when Object located between f and C Real or Virtual? Real Erect or Inverted? Inverted Same size, Enlarged or Reduced? Larger Location? Beyond C Concave Mirror

80. 80 Concave Mirror Object between f and C Light rays that travel parallel to the principle axis, strike the mirror, and are reflected back through the focal point (f). fC

81. 81 Concave Mirror Object between f and C Light rays that travel through the focal point (f), strike the mirror, and are reflected back parallel to the principle axis. fC

82. 82 Concave Mirror Object between f and C Image: Real Inverted Larger Beyond C The image is located where the reflected light rays intersect fC

83. 83 Concave Mirror with the Object located at f

84. 84 Concave Mirror Object at f Light rays that pass through the center of curvature hit the mirror and are reflected back along the same path.

85. 85 Concave Mirror Object at f Light rays that travel parallel to the principle axis, strike the mirror, and are reflected back through the focal point (f).

86. 86 Concave Mirror Object at f No image is formed. All reflected light rays are parallel and do not cross

87. 87 Concave Mirror with the Object located between f and the mirror

88. 88 Describe image when Object located between f and mirror Real or Virtual? Virtual Erect or Inverted? Erect Same size, Enlarged or Reduced? Larger Location? Further away, behind mirror Concave Mirror

89. 89 Concave Mirror Object between f and the mirror Light rays that travel through the focal point (f), strike the mirror, and are reflected back parallel to the principle axis.

90. 90 Light rays that travel parallel to the principle axis, strike the mirror, and are reflected back through the focal point (f). Concave Mirror Object between f and the mirror

91. 91 Concave Mirror Object between f and the mirror Image: Virtual Upright Larger Further away The image is located where the reflected light rays intersect

92. 92 Locating images in convex mirrors

93. 93 Convex Mirror with the Object located anywhere in front of the mirror

94. 94 Light rays that travel parallel to the principle axis, strike the mirror, and are reflected back through the focal point (f). f is negative. Convex Mirror Object located anywhere fC

95. 95 Light rays that travel through (toward) the focal point (f), strike the mirror, and are reflected back parallel to the principle axis. Convex Mirror Object located anywhere fC

96. 96 Convex Mirror Object located anywhere Image: Virtual Upright Smaller Behind mirror, inside f d i is negative The image is located where the reflected light rays intersect fC

97. THE MIRROR EQUATION The mirror equation can be used to locate the image: The ratio M is called the magnification, h o is the object’s size and h i is the image size. Where d o is the object’s distance, d i is the image distance and f is the focal length.

98. 98 d o = distance between object and mirror/lens d i = distance between image and mirror/lens h o = height of object h i = height of image m = optical enlargement of an object, ratio of size of image to size of object

99. Example Suppose you place a 5.0 cm tall pencil in front of a concave mirror. The mirror has a focal length of 24 cm. The pencil forms an image that appears to be at the same position as the spring, but the image is inverted. a. Where did you place the pencil? h o = 5 cm f = 24 cm d o = d i d o = 2f = 2(24cm) = 48 cm So… 2do2do = 1f1f

100. b. How tall is the pencil’s image? h o = 5 cm h i = -h o = - 5 cm h i h 0 =

101. Example Suppose you are 19 cm in front of the bell of your friend’s trumpet and you see your image at 14 cm. Treating the trumpet’s bell as a concave mirror, what would be its focal length and radius of curvature? d o = 19 cm d i = 14 cm f = 8.06 cm R = 2f = 2(8.06cm) = 16.12 cm 1 19cm = 1f1f 1 14cm +

102. 102 What type of mirror could have created the image shown above? –A. Plane –B. Concave –C. Convex Original Image

103. 103 Where would the object need to be placed to create this image? –A. At C –B. Between f and C –C. Beyond C –D. Between f and the mirror Original image

104. 104 Where would this image form? –A. At C –B. Between f and C –C. Beyond C –D. Between f and the mirror Original image

105. 105 If the focus of a convex mirror is 60 cm from the mirror, what is the radius of curvature? A. 120 cm B. -120 cm C. 30 cm D. -30 cm

106. 106 Convex mirror diagram An object is 5 meters in front of a convex mirror. The object is 1.5 meters tall. The mirror has a radius curvature of 12 meters.

107. 107 A man 2 m tall stands 10 m in front of a convex mirror which has a radius of curvature of 5 m. How tall is the image? A. 0.4 m B. -0.7 m C. 0.7 m D. 2 m Hint: must calculate to d i determine h i

108. 108 A concave mirror of radius 60 cm is placed so that a luminous object is 35 cm in front of the mirror. Where does the image form? A. Beyond C B. Behind mirror C. Between f and C a. 0.0048 cm b. 210 cm c. -0.012 cm d. -84 cm

109. 109 Get graph paper Starboard Documents Templates Linear Paper 207

110. 110 Draw the following ray diagram Ex 1 Concave mirror Center of curvature of mirror 10 cm Object 15 cm from mirror Object height is 2 cm Where is the image and how tall is it? Did the light rays converge at the image? Is it real or virtual?

111. 111 d i ~ 13.7cm in front of mirror h i = 1cm reduced and inverted -1cm Negative indicates inverted Rays converge, inverted real image

112. 112 Draw the following ray diagram Ex 2 Concave mirror Focal length 5cm Object 3 cm from mirror Object height is 2cm Where is the image and how tall is it? Did the light rays converge at the image? Is it real or virtual?

113. 113 d i ~ 4 cm behind mirror -4cm The negative indicates image is behind the mirroe h i = 3.5cm enlarged Rays do not converge, erect virtual image

114. 114 Draw the following ray diagram Convex mirror Center of curvature of mirror -10 cm Object 15 cm from mirror (why is this positive?) Object height is 3 cm Where is the image and how tall is it? Did the light rays converge at the image? Is it real or virtual?

115. 115 d i ~ -3.5cm The negative indicates image is behind the mirror h i = 1 cm reduced Rays do not converge, erect virtual image

116. 116 Where does object have to be to produce a virtual image? Between F and mirror Where does object have to be to produce a real image? Beyond F Were the real image always reduced? No

117. 117 Object Location Real or Virtual Erect or Inverted Size Plane Mirror Concave Mirror Convex Mirror

118. 118 Diagram from mirror lab

119. A curved mirror has a geometric center or vertex A The center of curvature or radius C The focal length f of the mirror is half the radius