1. Waves Intro
Chapter 25

2. Vocabulary Wave Medium Pulse
Vibratory disturbance that propagates (moves) through a medium
Medium
Material through which a wave propagates
Pulse
Single disturbance

3. Waves
Waves transfer energy from one place to another, not mass

4. Wave Types Two main types Transverse Longitudinal
Motion of the disturbance is perpendicular to the direction of the wave propagation
Longitudinal
Motion of the disturbance is parallel to the direction of the wave propagation

5. Transverse Waves
Motion of the disturbance is perpendicular to the direction of the wave propagation
Example: Light
TRANSVERSE WAVES

6. Longitudinal Waves
Motion of the disturbance is parallel to the direction of the wave propagation
Example: Sound
LONGITUDINAL WAVES

7. Surface Waves Combination of transverse and longitudinal waves
Example: Water

8. Water Waves (surface)

9. Wave Characteristics Amplitude, A (m) Wavelength, λ (m) Period, T (s)
Displacement away from equilibrium point
Wavelength, λ (m)
Length of 1 wave cycle
Period, T (s)
Amount of time for 1 wave cycle

10. Wave Characteristics (cont)
Crest
λ (m) A
T (s)
Trough

11. Wave Characteristics (cont)
Frequency, f (Hz or s-1)
Number of cycles per second
Inverse of period
Speed, v (m/s)
How fast wave is traveling
Related to frequency (period) and wavelength

12. Equations f = frequency (Hz) T = period (s) v = speed (m/s)
λ = wavelength (m)

13. Light Light is also called electromagnetic radiation
Light is a combination of fluctuating electric fields and magnetic fields that are perpendicular to each other

14. Electromagnetic Spectrum

15. Electromagnetic Spectrum
R Radiowave
M Microwave
I Infrared
V Visible
U Ultraviolet
X X-Rays
G Gamma
C Cosmic
Wavelength
Decreases
Frequency
Increases
Energy
Increases

16. Light (cont) Transverse Wave Travels through vacuum
Color is based on frequency
Green Light = 5.6 x 1014 Hz
Speed of light in a vacuum (air also)
c = 3 x 108 m/s

17. Sound Longitudinal Wave Needs a material (medium) to move
Pitch is based on frequency
Concert A = 440 Hz
Speed of Sound in air is dependent on Temp
v = 331 m/s at STP

18. Wave Speed Waves must follow the kinematic equation
The speed of waves depends upon the material that the wave travels through

19. Wave Speed Sound can not travel in a vacuum, light can
Light travels fastest in a vacuum, slower in all other materials
Sound travels faster in more dense materials

20. Phase Difference
Two points are considered “in phase” when they are at the same point in a wave cycle
The amount of “in or out of phase” is measured in degrees

21. Phase Difference Examples
What point is in phase with A?
B and D are how far out of phase?
Name two other points in phase with each other.

22. Wave Motion
Waves propagate in all directions without barriers

23. Wave Fronts
Line that represents waves that are all in phase, usually crests

24. Principle of Superposition
When two waves meet, they combine together briefly, then go their separate ways
Crest + crest = bigger amplitude
Trough + trough = bigger amplitude
Crest + trough = lower amplitude

25. Interference Constructive Interference Destructive Interference
When 2 waves interfere with resultant wave having larger amplitude
Destructive Interference
When 2 waves interfere with resultant wave having smaller amplitude

26. Simulation Examples

27. Interference Example Two point sources (green dots)
What do the red dots represent?
What do the blue dots represent?

28. Sound Beats Interference produced when two sounds interact
Frequency of beats is equal to difference of frequencies of two sounds
Concept used to tune pianos
Demo

29. Doppler Effect
Change in frequency due to moving wave source or observer
Example

30. Doppler Effect
When distance between source and observer is decreasing, frequency increases
Blue Shift
When distance between source and observer is increasing, frequency decreases
Red Shift

31. Sonic Boom
When moving object exceed the speed of sound, air builds up into a shock wave

32. Sonic Boom

33. Standing Waves
Occurs when two waves traveling in opposite directions in the same medium, with the same amplitude and same frequency
Resultant wave appears to be standing still
Demo

34. Nodes and Antinodes Nodes Antinodes
Points of maximum destructive interference
Antinodes
Points of maximum constructive interference

35. Nodes and Antinodes

36. Nodes and Antinodes

37. Video
YouTube Video
How does this work?

38. Resonance Natural Frequency Resonance
Particular frequency that every elastic body will vibrate at if disturbed
Resonance
Vibration of a body at its natural frequency because of the action of a vibrating source of the same frequency

39. Real Life
Microwaves produce waves that have the same frequency as the vibrational frequency of water molecules
UV rays have the same frequency as certain chemicals in human skin, causing sun burns
Google – Tacoma Narrows Bridge

41. Sound
Chapter 26

42. Vocabulary Wave Medium Pulse
Vibratory disturbance that propagates (moves) through a medium
Medium
Material through which a wave propagates
Pulse
Single disturbance

43. Waves Waves transfer energy from one place to another, not mass
Sound must have a medium to travel through
Sound can not travel in a vacuum
No Sound is space

44. Longitudinal Waves
Motion of the disturbance is parallel to the direction of the wave propagation
Example: Sound
LONGITUDINAL WAVES

45. Longitudinal Waves Compression – area of compacting molecules
Rarefaction – area of low pressure between compressions
LONGITUDINAL WAVES

46. Wave Characteristics Amplitude, A (m) Wavelength, λ (m) Period, T (s)
Displacement away from equilibrium point
Wavelength, λ (m)
Length of 1 wave cycle
Period, T (s)
Amount of time for 1 wave cycle

47. Wave Characteristics (cont)
Crest
λ (m) A
T (s)
Trough

48. Wave Characteristics (cont)
Frequency, f (Hz or s-1)
Number of cycles per second
Inverse of period
Pitch is based on frequency
Concert A = 440 Hz
Human Hearing ranges from 20-20,000 Hz

49. Equations f = frequency (Hz) T = period (s) v = speed (m/s)
λ = wavelength (m)

50. Speed of Sound
The speed of sound depends upon the material that it travels through
Sound travels faster in more dense materials
Speed of Sound in air is dependent on Temp
v = m/s at STP

51. Echo Reflection of sound bouncing off an object
Radar and Sonar use this concept
Remember: time to hear echo is for double distance (there and back again)

52. Doppler Effect
Apparent change in frequency due to moving wave source or observer
When distance between source and observer is decreasing, frequency increases
Blue Shift
When distance between source and observer is increasing, frequency decreases
Red Shift
Example

53. Interference
When two waves meet, they combine together briefly, then go their separate ways
Constructive Interference
When 2 waves interfere with resultant wave having larger amplitude
Destructive Interference
When 2 waves interfere with resultant wave having smaller amplitude

54. Sound Beats Interference produced when two sounds interact
Frequency of beats is equal to difference of frequencies of two sounds
Concept used to tune pianos
Demo

55. Standing Waves
Occurs when two waves traveling in opposite directions in the same medium, with the same amplitude and same frequency
Nodes
Points of maximum destructive interference
Antinodes
Points of maximum constructive interference

56. Nodes and Antinodes

57. Nodes and Antinodes

58. Resonance Natural Frequency Resonance
Particular frequency that every elastic body will vibrate at if disturbed
Resonance
Vibration of a body at its natural frequency because of the action of a vibrating source of the same frequency

59. Harmonics Fundamental Frequency(1st Harmonic)
Lowest frequency possible
2nd Harmonic
2x frequency of 1st Harmonic (Octave higher)

60. Closed Pipe Harmonics 1st Harmonic L = 1/4 3rd Harmonic L = ¾ 
5th Harmonic L = 1 1/4 
 = 4/5L

61. Open Pipe Harmonics 1st Harmonic L = ½ =2L 2nd Harmonic L = 
3rd Harmonic L = 1 ½ 
=2/3L

63. Light and Color
Chapters 27 & 28

64. Review Wavelength Frequency Period Amplitude Length of one wave cycle
Number of cycles per second
Period
Amount of time for one cycle
Amplitude
Displacement away from equilibrium point

65. Wave Characteristics (cont)
Crest
λ (m) A
T (s)
Trough

66. Equations f = frequency (Hz) T = period (s) v = speed (m/s)
λ = wavelength (m)

67. Transverse Waves
Motion of the disturbance is perpendicular to the direction of the wave propagation
Example: Light
TRANSVERSE WAVES

68. Light Light is also called electromagnetic radiation
Light is a combination of fluctuating electric fields and magnetic fields that are perpendicular to each other

69. Light (cont) Transverse Wave Travels through vacuum
Color is based on frequency
Green Light = 5.6 x 1014 Hz
Speed of light in a vacuum (air also)
c = 3 x 108 m/s

70. Light How long does the light from the sun take to each Earth? 500s
~8min

71. Electromagnetic Spectrum

72. Electromagnetic Spectrum
R Radiowave
M Microwave
I Infrared
V Visible
U Ultraviolet
X X-Rays
G Gamma
C Cosmic
Wavelength
Decreases
Frequency
Increases
Energy
Increases

73. Light
Light Year
Distance light travels in one year
9.46x1015m

74. Color Color of light is based on frequency Color Addition (Light)
All colors added together produces white light
Color Subtraction (Art)
All colors “added” together produce black

75. Primary Colors Red, Green, Blue Red + Blue =Magenta
Red + Green = Yellow
Blue + Green = Cyan
Secondary Colors

76. Complementary Colors Two Colors that when added together produce white
Blue + Yellow
Green + Magenta
Red + Cyan

77. Polarization
Process by which non-polarized light is transformed into polarized light
Doesn’t work for sound
Polarized Light has the wave vibrations occurring in a single plane

78. Polarization
Non-polarized light has wave vibrations in all directions

80. Reflection
Chapter 29

81. Reflection
When a wave encounters a new medium or barrier some of the wave is bounced back (reflected), and some is transmitted (refracted)
Simulation

82. Law of Reflection Angle of Incidence = Angle of Reflection θi = θr
Always measured from Normal(Perpendicular) θi θr

83. Types of Reflection Regular Reflection Diffuse Reflection
Reflection of light from a smooth surface
Diffuse Reflection
Reflection of light from a rough surface

84. Image Types Real – Light rays actually travel to that location
Virtual – Light appears to be at that location
Upright – image is right side up compared to object
Inverted – image is upside down as compared to object

85. Plane (flat) Mirror Mirror The light we see appears to originate
from the other side of the mirror

86. Curved Mirrors Concave Mirrors Convex Mirrors
Can produce real or virtual images
Rear View Mirrors on Cars
Convex Mirrors
Always produce virtual images
Image is always smaller

87. Curved Mirrors Portion of a circle
Center of Curvature (C) is located at the center of the Circle
Focal Length (focal point) (f) is located halfway between the center of curvature and the mirror along the optical axis C f

88. Concave Mirrors Drawing Ray Diagrams
Any ray entering through the center of curvature will, after interaction with the optical device (mirror), leave (or appear to leave) through the center of curvature C f

89. Concave Mirrors Drawing Ray Diagrams
Any ray entering parallel to the optical axis will, after interaction with the optical device (mirror), leave (or appear to leave) through the focal point C f

90. Concave Mirrors Drawing Ray Diagrams
Any ray entering through the focal point will, after interaction with the optical device (mirror), leave (or appear to leave) parallel to the optical axis C f

91. Concave Mirrors C f

92. Convex Mirrors
Same Rays as concave C f

93. Mirror Simulation
Simulation

94. Mirrors Object distance, do Image distance, di
Where the object is located
Image distance, di
Where the image is located
Negative distance is located “inside” mirror, opposite side

95. Mirrors
Object size, So
Image size, Si
Negative means inverted

96. Mirror Equations
M = Magnification

97. Review Law of Reflection Angle of Incidence = Angle of Reflection
θi = θr

98. Distance Positive distance is in front of mirror
Object distance, do=o
Where the object is located, distance from mirror
Image distance, di=i
Where the image is located, distance from mirror
Positive distance is in front of mirror
Negative distance is located “inside” mirror, opposite side, behind mirror

99. Size Object size, So Image size, Si Magnification, M
Is image bigger or smaller
Negative means inverted

100. Images All real images Virtual Images have a (+)di Have a (–)di
Inverted, (-)M
Virtual Images
Have a (–)di
Upright, (+)M

101. Principle Rays for Curved Mirrors
In parallel, out through focal point (f)
In through Focal point (f), out parallel
In through Center of Curvature (C), out through Center of Curvature (C)
Incident at center of mirror, reflected at same angle out from center of mirror

103. Refraction
Chapters 29

104. Question Imagine running down the road
how fast are you going?
Imagine running in thick mud Thicker Material
How fast are you going? Speed decreases
How long is your stride? Wavelength decreases

105. Refraction
Changing of speed when wave enters new material (frequency remains constant)
Speed decreases in more dense material
Wavelength decreases
Speed increases in less dense material
Wavelength increases

106. Refraction Example
Freqair=Freqwater because the color remains the same
Since the wavelength changes, the velocity must change proportionately
Air
Water

107. Index of Refraction (n)
Measure of the optical density of a material
Table in the Reference Tables

108. Refraction When a wave enters a new medium, it changes speed.
When a wave enters a new medium, it changes direction

109. Refraction

110. Refraction
Simulation

111. Snell’s Law
n1 sin θ1 = n2 sin θ2
Air
Water θi θr

112. Snell’s Law
When a wave enters a more dense material, the wave will bend TOWARDS the normal
When a wave enters a less dense material, the wave will bend AWAY from the normal

113. Example n1 sin θ1 = n2 sin θ2 θr= 58.7° Air Water n = 1.00 n = 1.33
40°

114. Dispersion Spreading of light into its color components
Index of refraction is based on frequency of light
Index varies for different frequencies

115. Dispersion

116. Dispersion

117. Rainbows

118. Example θi= 47° θr= 76.6° θi= 48° θr= 81.3°
Air
Water
n = 1.00
n = 1.33
θi= 47° θr= 76.6°
θi= 48° θr= 81.3°
θi= 49° θr= ? Is there a problem?
θr=?

119. Critical Angle, θc
At a certain incident angle the refracted ray will be at 90°.
Total Internal Reflection
At angles greater than the Critical Angle, the ray is reflected back into the material. θi
Air
Water
n = 1.00
n = 1.33 θr

120. Critical Angle n1 sin θC = n2 sin θ2 sin θ2 = 1 n1 sin θC = n2

121. Total Internal Reflection
For angles larger than the critical angle, all of the light is reflected inward
Fiber Optic Cable

123. Lenses
Chapter 30

124. Vocabulary Object distance, o Image distance, i
Distance object is from optical device
Image distance, i
Distance image is from optical device

125. Vocabulary
Object size, So
Size of object
Image size, Si
Size of image

126. Vocabulary
Real Image
Image formed by actual intersection of light rays
Image can be projected on a screen

127. Vocabulary Virtual Image (imaginary)
Light rays do not travel to that location, only appear to travel there
Image can NOT be projected on screen

128. Lenses Equation

129. Lenses Converging Lenses Diverging Lenses Biconvex f=(+) Biconcave

130. Converging Lens Rays
Ray that is initially parallel to central axis will refract through far focal point
Ray that is initially through near focal point will refract parallel to central axis
Ray that passes through center of lens pass without refraction

131. Converging Lens

132. Converging Lens Example
f = 10 cm
i= ?
o = 20 cm
i= 20 cm
M = 1

133. Diverging Lens Rays
Ray that is initially parallel will refract as if coming from near focal point
Ray that is initially through far focal point will refract as if coming from parallel
Ray that passes through center will continue on

134. Diverging Lens

135. Diverging Lens Example
o = 25 cm
f = -10 cm
i = ?
i = cm
M = 0.3

136. Example
Applet

137. How the Eye works Light enters the eye through the cornea
Outer layer covering the eye (n=1.38)
Travels through the aqueous humor
fluid between cornea and lens
Travels through the pupil
Empty black space created by the Iris (colored part)

138. How the Eye works Refracted through the lens
Travels through vitreous humor
Fluid inside of the eye
Image is on the retina
Back of eye with light receptors
Optic nerve transmits information to Occipital lobe of the brain where the image is interpreted

139. How the Eye works

140. Eye problems Nearsightedness (Myopia) Farsightedness (Hyperopia)
Image is focused in front of the retina
Farsightedness (Hyperopia)
Image is focused behind the retina
Astigmatism
Irregular curvature of lens or cornea

141. Lenses in Combination
Image from the first lens becomes the object for the second lens
Microscope
Telescope
Galilean (refracting)
Keplerian (refracting)
Newtonian (reflecting)

142. Lenses in Combination

143. Lenses in Combination do1 = 25 cm f2 = 8 cm di2 = 12 cm f1 = 10 cm

144. Aberrations Distortions in an image
Combining lenses can minimize the aberrations

145. Aberrations Spherical Aberrations
Results when light passes through the edges of a lens (mirrors also)

146. Aberrations Chromatic Aberrations
Different speeds of light for different colors

148. Diffraction
Chapters 31

149. Wave Motion
Waves propagate in all directions without barriers

150. Wave Fronts
Line that represents waves that are all in phase, usually crests

151. Huygens Principle
Every point on a propagating wave front serves as a source of a spherical secondary wavelet
The corresponding spherical wavelets produce further wave fronts
Basis for Diffraction, Reflection, Refraction

152. Huygens Principle

153. Huygens Principle

154. Huygens Principle First proposed explanation that light is a wave
Newton later proposed that light is a particle

155. Diffraction
Bending of waves around an obstacle or the edges of an opening
Example:
You can often hear people in the hallway without seeing them
Shadows

156. Sound Diffraction

157. Diffraction

158. Diffraction

159. Diffraction
Causes interference patterns a certain distance away from the source
Bright and dark spots for light
Loud and dead spots for sound
Amount of diffraction is a measure of distance between consecutive bright spots

160. Young’s Double Slit Experiment
Proof that light acts like a wave
Light shining through 2 slit opening
Bright and dark lines on screen

161. Diffraction Equation x = amount of diffraction λ = wavelength
L = distance from opening to screen
d = distance between slits
d<<L

163. Examples
Applet
Laser Pointer

164. Path Difference

165. Path Difference
For Maximum Constructive Interference the path difference is nλ
For Maximum Destructive Interference, the path difference is (n +1/2)λ