1. Chapter 5 Let Us Entertain You. Sound and Light

2. How do stringed instruments make notes?

3. Guitar Ukelele

4. Koto Violin How do stringed instruments make notes?

5. Piano Harp How do stringed instruments make notes?

6. A word about pitch: High note = High pitch = High frequency Low note = Low pitch = Low frequency

7. A vibrating string: What affects the frequency of vibration?

8. Frequency is…… ______________related to the ___________ of the tension on the string ______________related to the ___________ of the length of the string ______________related to the ___________ of the mass of the string

9. Frequency is…… ____Directly___ related to the _square root_ of the tension on the string ___Inversely___ related to the _square root_ of the length of the string ___Inversely___ related to the _square root_ of the mass of the string

10. Frequency is…. f= T 4mL

11. Waves: Carry energy (Greater amplitude  more energy) Have a velocity, wavelength, frequency and amplitude (Frequency and wavelength are inversely related) Velocity depends on the medium Interfere (add up) Can be transverse (↕) or longitudinal (↔)

12. The wave equation: Velocity = frequency x wavelength v = f (m/s) = (/s) x (m) (frequency and wavelength are inversely related)

13. Calculate: 1)Waves on water have a wavelength of 2.0 m, and a frequency of 3 Hz (3 waves / second). What is their speed? 2) A vibrating guitar string has a frequency of 512 Hz, carrying a wave that moves at 320 m/s. What is its wavelength? 3)What is the frequency of a radio wave that travels at 3.00 x 10 8 m/s and has a wavelength of 3.134 m?

15. Wave motion 

16. Motion of medium

17. What is the wavelength in each case

18. Woodwinds. The resonance of sound in an open tube: Please notice the antinodes at the open ends.

19. Woodwinds. What is the length of the entire wave?

20. Woodwinds. What is the length of the entire wave? The tube holds half a wave, so =2L

21. Other resonance modes: What is the wavelength in each case?

22. In a tube of air, the length of the tube is…

23. If one end is closed: There is a node at the closed end, and an antinode at the open end.

24. If one end is closed: There is a node at the closed end, and an antinode at the open end. What is the length of the wave?

25. If one end is closed: There is a node at the closed end, and an antinode at the open end. One-fourth of the wave fits into the tube, so =4L.

26. Other resonance modes: What is the wavelength in each case?

28. HW p 526 1) (Pretty good) Similar: vibrations make sound, frequency and wavelengths Different: String vibrating makes air vibrate vs air itself vibrates

29. HW p 526 2) a. Did you draw them (3 or 4) full-sized? b.

30. HW p 526 2) b. (cont’d) c) longest wavelenths=lowest frequencies

31. HW p 526 3)answers vary (2.4 m normally—19.5 m record) b. c. L of pipe= ¼ wavelength (wavelength=4 x L of pipe) d freq and wavelength are inversely related.

32. HW p 526 4) L of pipe= ¼ wavelength (wavelength=4 x L of pipe) f=v/ 5)Which is higher? How much higher freq.? f=v/  freq and wavelength are inversely related. 6) t=d/v

33. Apply the wave equation: 1.A wave has a frequency of 58 Hz and a speed of 31 m/s. What is the wavelength of this wave? 2.A periodic transverse wave is established on a string such that there are exactly two cycles on a 3.0-m section of the string. The crests move at 20 m/s. What is the frequency of the wave? 3.A 4-m long string, clamped at both ends, vibrates at 200 Hz. If the string resonates in six segments, what is the speed of transverse waves on the string? 4.Four standing wave segments, or loops, are observed on a string fixed at both ends as it vibrates at a frequency of 140 Hz. What is the fundamental frequency of the string? 5.Vibrations with frequency 600 Hz are established on a 1.33-m length of string that is clamped at both ends. The speed of waves on the string is 400 m/s. How many waves are on the string?

34. Light Light is a transverse wave (an electromagnetic wave) Light travels in a straight line

35. Light A shadow falls where light is blocked Shadow No shadow

36. Light A shadow falls where light is blocked…BUT! Shadow No shadow

37. Light A shadow falls where light is blocked…BUT…a real light source is not a single point.

38. Light A shadow falls where light is blocked…BUT…a real light source is not a single point. Shadow from the right side of the bulb

39. Light A shadow falls where light is blocked…BUT…a real light source is not a single point. Shadow from the left side of the bulb

40. Light A shadow falls where light is blocked…BUT…a real light source is not a single point. Overlapping shadows (umbra)

41. Light A shadow falls where light is blocked…BUT…a real light source is not a single point. Non-overlapping shadow (penumbra)

42. Light A shadow falls where light is blocked…BUT…a real light source is not a single point. Light from both sides (no shadow)

43. Umbra and Penumbra

45. Tracing Rays.

48. didi dodo

49. didi dodo

50. d i =d o The image is directly behind the mirror at the same distance the object is in front of the mirror didi dodo

51. Tracing Rays II

54. Measure angle of incidence Measure angle of reflection

55. Angle of incidence=angle of reflection

56. Curved mirrors A convex mirror takes light rays parallel to the axis and makes reflected rays that diverge

57. Curved mirrors The reflected light seems to come from a single point behind the mirror, the focus focus

58. Curved mirrors A concave mirror takes light rays parallel to the axis and makes reflected rays that converge

59. Curved mirrors The reflected light goes through a single point in front of the mirror, the focus focus

60. So, where’s the image?

61. It depends.

62. Curved mirrors In a convex mirror, an image is formed where the rays seem to come from.

63. Curved mirrors The image is upright, smaller, and can be seen in the mirror.

64. Curved mirrors In a concave mirror, the image is inverted (upside down) and can be projected onto a screen

65. Curved mirrors Here, the image is smaller than the object.

66. Curved mirrors …but you can make a real image just as large…

67. Curved mirrors …or even larger than the object.

68. Did you notice? As d o gets smaller, d i gets larger!

69. Did you also notice? As d o gets smaller, d i gets larger! As d i gets larger, h i gets larger!

70. A concave mirror can also make a virtual image.

71. Draw three rays. 1) Parallel to the axis—reflects through the focus

72. Draw three rays. 1) Parallel to the axis—reflects through the focus

73. Draw three rays. 2) To the center—reflects like a flat mirror

74. Draw three rays. 2) To the center—reflects like a flat mirror

75. Draw three rays. 3) To the focus—reflects parallel to the axis

76. Draw three rays. 3) To the focus—reflects parallel to the axis

77. Draw three rays. All together:

78. Draw three rays. All together

79. Rules, rules, rules. 1)A real image has a positive d i and h i. It is inverted (upside down = positive height!) 2)A virtual image has a negative d i and h i. It is upright (right side up = negative height!) 3)A real image has a real location—put a screen there. A virtual image has a virtual location, it looks like it is there in the mirror.

80. Rules, rules, rules. 4) A virtual image can be larger, the same size or smaller than the object larger—in a concave mirror the same size—in a flat mirror smaller—in a convex mirror 5) A real image can be larger, the same size or smaller than the object larger—if d i is larger than d o the same size—if d i is equal to d o smaller—if d i is smaller than d o

81. The lens equation. (I know, we’re using mirrors, it’s the same equation) 1=1+1 fd o d i

82. The lens equation. (I know, we’re using mirrors, it’s the same equation) 1=1+1 fd o d i andd i =h i d o h o

83. What do you notice?

84. If you pull the object in (decreasing d o ), the image moves away from the focus (increasing d i ) As the image moves away from the focus, it gets larger.

85. Describe the image formed: 1. A 12.0 cm object is placed 24.0 cm. from a concave mirror with a focal length of 18.0 cm. d o =24.0cm d i = f=18.0 cm h o =12.0 cm h i =

86. Describe the image formed: 1. A 12.0 cm object is placed 24.0 cm. from a concave mirror with a focal length of 18.0 cm. d o =24.0cm d i =72.0 cm  Real image! f=18.0 cm h o =12.0 cm h i =36.0 cm  Inverted and larger!

87. Describe the image formed: 2. A 8.0 cm object is placed 15.0 cm. from a concave mirror with a focal length of 6.0 cm. d o =15.0 cm d i = f=6.0 cm h o =8.0 cm h i =

88. Describe the image formed: 2. A 8.0 cm object is placed 15.0 cm. from a concave mirror with a focal length of 6.0 cm. d o =15.0 cm d i =10.0 cm  Real image! f=6.0 cm h o =8.0 cm h i =5.33 cm  Inverted and smaller!

89. Describe the image formed: 3. A 6.0 cm object is placed 4.0 cm. from a concave mirror with a focal length of 6.0 cm. d o =4.0 cm d i = f=6.0 cm h o =6.0 cm h i =

90. Describe the image formed: 3. A 6.0 cm object is placed 4.0 cm. from a concave mirror with a focal length of 6.0 cm. d o =4.0 cm d i = -12.0 cm  Virtual image! f=6.0 cm h o =6.0 cm h i =-18.0 cm  Upright and larger!

91. Describe the image formed: 4. A 12.0 cm object is placed 12.0 cm. from a convex mirror with a focal length of -18.0 cm. d o =12.0 cm d i = f=-18.0 cm h o =12.0 cm h i =

92. Describe the image formed: 4. A 12.0 cm object is placed 12.0 cm. from a convex mirror with a focal length of -18.0 cm. d o =12.0 cm d i =-7.20 cm  Virtual image! f=-18.0 cm h o =12.0 cm h i =-7.20 cm  Upright and smaller!

93. Refraction of light. Light bends when it enters or leaves a transparent object.

94. Refraction of light. Light bends when it enters or leaves a transparent object…because light travels more slowly in the substance. Light slows down Light speeds up

95. Which way does it bend? How far?

96. Measure from the normal line Angle of incidence Angle of refraction

97. Snell’s Law The index of refraction for a substance, n, is defined: n=sin i sin r Angle of incidence Angle of refraction

98. Snell’s Law Light bends towards the normal as it enters a substance from air. Angle of incidence Angle of refraction

99. Snell’s Law Light bends away from the normal as it leaves a substance to air. Angle of incidence Angle of refraction

100. Snell’s Law The index of refraction relates the sines of the angles. Angle of incidence Angle of refraction

101. Pop quiz: For what angle, , is Sin  >1 ?

102. Pop quiz: For what angle, , is Sin  >1 ? None!

103. Snell’s Law Light leaves the substance when it can… Angle of incidence Angle of refraction

104. Snell’s Law Light leaves the substance when it can…but how far away from the normal can it bend? Angle of incidence Angle of refraction

105. Snell’s Law ?

106. Total internal reflection!

107. Snell’s Law Total internal reflection! Critical angle! When angle of refraction= 90 o

108. Try this one:

113. Or:

116. A diamond has a large index of refraction (=small critical angle)

117. Or: It is cut so that all light reflects off the bottom, escapes out of the top