1. Waves— Sound and Light
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2. This lecture will help you understand:
Vibrations and Waves
Wave Motion
Transverse and Longitudinal Waves
The Nature of Sound
Resonance
The Nature of Light
Reflection
Transparent and Opaque Materials
Color
Refraction
Diffraction
Interference
The Doppler Effect
The Wave–Particle Duality
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3. Vibrations and Waves A vibration is a wiggle in time.
A wave is a wiggle in space and time—a disturbance that travels from one place to another transporting energy.
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4. Vibrations and Waves
A vibration is described in terms of frequency—how frequently vibratory motion occurs.
A wave is described in terms of frequency, speed, amplitude, and wavelength.
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5. Vibrations and Waves Frequency:
The number of to-and-fro vibrations in a given time
Unit: 1 vibration per second = 1 Hertz
Period:
The time it takes for a complete vibration
Unit: any unit of time, often the second
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6. Vibrations and Waves Relationship between frequency and period:
Frequency = 1/period
Unit: Hertz (Hz)
Period = 1/frequency
Unit: second (s)
The source of all waves is a vibration.
Higher frequency means increased rate of energy transfer. Pulses occur more frequently and produce waves that are more closely spaced—shorter wavelengths.
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7. Vibrations and Waves CHECK YOUR NEIGHBOR
If the frequency of a particular wave is 20 Hz, its
period is
1/20 second.
20 seconds.
more than 20 seconds.
none of the above
Explain your answer to your neighbor.
A. 1/20 second.
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8. Vibrations and Waves CHECK YOUR ANSWER
If the frequency of a particular wave is 20 Hz, its
period is
1/20 second.
20 seconds.
more than 20 seconds.
none of the above
Explanation:
When f = 20 Hz, T = 1/f = 1/(20 Hz) = 1/20 second.
A. 1/20 second.
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9. Wave Motion
Wave motion is the propagation of a disturbance through a medium.
The medium transporting the wave returns to its initial condition after the disturbance has passed.
Wave motion requires an energy source and a medium (except for light) through which the energy is transferred.
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10. Wave Motion Wave characteristics: Crest—highest point
Trough—lowest point
Wavelength
Amplitude
Frequency
Period
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11. Wave Motion CHECK YOUR NEIGHBOR
The distance between adjacent peaks in the
direction of travel for a transverse wave is its
frequency.
period.
wavelength.
amplitude.
Explain your answer to your neighbor.
C. wavelength.
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12. Wave Motion CHECK YOUR ANSWER
The distance between adjacent peaks in the direction of
travel for a transverse wave is its
frequency.
period.
wavelength.
amplitude.
Explanation:
The wavelength of a transverse wave is also the distance
between adjacent troughs, or between any adjacent
identical parts of the waveform
C. wavelength.
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13. Wave Motion
Wave speed
describes how fast the disturbance moves through the medium.
is related to the frequency and wavelength of the wave.
Equation for wave speed:
Wave speed = frequency  wavelength
v = 
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14. Transverse and Longitudinal Waves
Two different types of waves are classified by the direction in which the medium vibrates compared to the direction of energy travel.
Transverse wave: Vibration is at right angles (sideways) to wave travel.
Longitudinal wave: Vibration is in the direction of travel.
Wave travel consists of compression and rarefaction components.
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15. Transverse and Longitudinal Waves CHECK YOUR NEIGHBOR
The vibrations along a transverse wave move in a
direction
along the wave.
perpendicular to the wave.
both of the above
neither of the above
Explain your answer to your neighbor.
B. perpendicular to the wave.
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16. Transverse and Longitudinal Waves CHECK YOUR ANSWER
The vibrations along a transverse wave move in a direction
along the wave.
perpendicular to the wave.
both of the above
neither of the above
Comment:
The vibrations in a longitudinal wave, in contrast, are along
(or parallel to) the direction of wave travel.
B. perpendicular to the wave.
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17. The Nature of Sound
Sound travels in longitudinal waves consisting of vibrating compressions and rarefactions through the air.
Speed of sound: Sound travels at 340 m/s in air at 20°C.
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18. The Nature of Sound A situation to ponder…
Consider a person attending a concert that is being broadcast over the radio. The person sits about 45 m from the stage and listens to the radio broadcast with a transistor radio over one ear and a nonbroadcast sound signal with the other ear. Further suppose that the radio signal must travel all the way around the world before reaching the ear.
Put the correct answer here including the letter designation.
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19. A situation to ponder… CHECK YOUR NEIGHBOR
Which signal will the person hear first?
Radio signal
Nonbroadcast sound signal
Both at the same time
none of the above
Explain your answer to your neighbor.
C. Both at the same time.
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20. A situation to ponder… CHECK YOUR ANSWER
Which signal will the person hear first?
Radio signal
Nonbroadcast sound signal
Both at the same time
none of the above
Explanation:
A radio signal travels at the speed of light—3  108 m/s.
Time to travel 45 m at 340 m/s ≈ 0.13 s.
Time to travel 4  107 m (Earth’s circumference) at
3  108 m/s ≈ 0.13 s.
So, if you sit farther back at the concert, the radio signal will reach you
first!
C. Both at the same time.
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21. The Nature of Sound
For each increase of 1°C above 0°C, the speed of sound increases by 0.6 m/s.
Order of increasing speeds of sound:
In air (≈ 340 m/s)
In warm air (>340 m/s)
In water (≈ four times speed in air)
In steel (≈ 15 times speed in air)
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22. Resonance
Resonance occurs whenever successive impulses are applied to a vibrating object in rhythm with its natural frequency.
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23. The Nature of Light
Light is electromagnetic waves created by vibrating electric charges with frequencies that fall within the range of sight.
The frequency of vibrating electrons equals the frequency of the light.
Light travels nearly a million times
faster than sound in air.
Light and all electromagnetic
waves are transverse waves.
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24. The Nature of Light The electromagnetic spectrum
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25. The Nature of Light CHECK YOUR NEIGHBOR
The electromagnetic spectrum is a span of electromagnetic
waves, ranging from lowest to highest frequencies. The
smallest portion of the electromagnetic spectrum is that of
radio waves.
microwaves.
visible light.
gamma rays.
Explain your answer to your neighbor.
C. visible light.
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26. The Nature of Light CHECK YOUR ANSWER
The electromagnetic spectrum is a span of electromagnetic
waves, ranging from lowest to highest frequencies. The
smallest portion of the electromagnetic spectrum is that of
radio waves.
microwaves.
visible light.
gamma rays.
Explanation:
The answer can be inferred from a careful study of the
spectrum and its regions in Figure 8.10.
C. visible light.
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27. © 2013 Pearson Education, Inc.

28. The Nature of Light Order of increasing frequency of visible light:
Red
Violet—nearly twice the frequency of red
Ultraviolet—cause sunburns
X-rays
Gamma rays
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29. The Nature of Light
Electromagnetic waves are composed of perpendicular electric and magnetic fields that vibrate perpendicular to the direction of wave travel. The electric and magnetic fields regenerate each other by electromagnetic induction.
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30. The Nature of Light A situation to ponder…
A photographer wishes to photograph a lightning bolt by setting his camera so that it is triggered by the sound of thunder.
Put the correct answer here including the letter designation.
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31. A situation to ponder… CHECK YOUR NEIGHBOR
Is this a good idea or a poor idea?
Good idea for nearby lightning strikes
Good idea for all strikes
Poor idea for nearby lightning strikes
Poor idea for all strikes
Explain your answer to your neighbor.
D. Poor idea for all strikes.
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32. A situation to ponder… CHECK YOUR ANSWER
Is this a good idea or a poor idea?
Good idea for nearby lightning strikes
Good idea for all strikes
Poor idea for nearby lightning strikes
Poor idea for all strikes
Explanation:
Light travels about a million times faster than sound. By the
time the sound of thunder arrives, the lightning bolt is long
gone.
D. Poor idea for all strikes.
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33. Reflection
Reflection is the returning of a wave to the medium through which it came when it encounter a reflective surface
Law of reflection:
Angle of incidence = angle of reflection
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34. Reflection Diffuse reflection
When light is incident on a rough surface, it is reflected in many directions.
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35. Reflection CHECK YOUR NEIGHBOR
Compared with a dry road, seeing is more difficult when
driving at night on a wet road. Why?
A wet surface is smooth with less diffuse reflection, part of which would otherwise reach the driver’s eyes.
A wet road usually means a wet windshield.
A wet road usually means more vapor in the air.
There is no reason—that’s just the way it is.
Explain your answer to your neighbor.
A. Wet surface is smooth with less diffuse reflection, part of which would otherwise reach the driver’s eyes.
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36. Reflection CHECK YOUR ANSWER
Compared with a dry road, seeing is more difficult when
driving at night on a wet road. Why?
A wet surface is smooth with less diffuse reflection, part of which would otherwise reach the driver’s eyes.
A wet road usually means a wet windshield.
A wet road usually means more vapor in the air.
There is no reason—that’s just the way it is.
A. Wet surface is smooth with less diffuse reflection, part of which would otherwise reach the driver’s eyes.
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37. Transparent and Opaque Materials
Transparent materials
Light passes through transparent materials in straight lines, with atoms undergoing a series of absorptions and reemissions.
Examples: glass, water
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38. Transparent and Opaque Materials
Colored glass is opaque to much of incident white light.
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39. Color
The Color that we see depends on the frequency of light, ranging from lowest (red) to highest (violet). In between are the colors of the rainbow.
Hues in seven colors: red, orange, yellow, green, blue, indigo, and violet
Grouped together, they add to appear white.
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40. Color Selective reflection
Most objects don’t emit light, but reflect light.
A material may absorb some of the light and reflect the rest.
Selective transmission
The color of a transparent object depends on the color of the light it transmits.
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41. Color Mixing Colored lights (integrated)
Three types of cone receptors in our eyes perceive color.
Each is stimulated by only certain frequencies of light.
Light of lower frequencies stimulates the cones sensitive to low frequencies (red).
Light of middle frequencies stimulates the cones sensitive to mid-frequencies (green).
Light of high frequencies stimulates the cones sensitive to high frequencies (blue).
when all three cones are stimulated equally, we see white light.
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42. Color Additive primary colors (red, blue, green): Red + blue = magenta
Red + green = yellow
Blue + green = cyan
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43. Color Opposites of primary colors: The opposite of green is magenta.
The opposite of red is cyan.
The opposite of blue is yellow.
The addition of any color to its opposite color results in white.
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44. Color CHECK YOUR NEIGHBOR
To which radiation is the human eye blind?
Infrared
Ultraviolet
Both infrared and ultraviolet
Neither infrared nor ultraviolet
Explain your answer to your neighbor.
C. Both of the above.
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45. Color CHECK YOUR ANSWER
To which radiation is the human eye blind?
Infrared
Ultraviolet
Both infrared and ultraviolet
Neither infrared nor ultraviolet
C. Both of the above.
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46. Refraction Refraction is the bending of a wave due to a change
in the medium and/or
speed of the wave.
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47. Refraction Examples of refraction: When light slows down in
going from one medium to
another, as when going from
air to water, it bends toward
the normal.
When light speeds up in traveling
from one medium to another, as
when going from water to air, it
bends away from the normal.
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48. Refraction
Sound waves refract when parts of the wave fronts travel at different speeds.
Refraction occurs when sound waves are affected by uneven winds, or when air near the ground is warmer than the air above.
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49. Refraction Lenses are classified into two kinds:
Converging lens: Incoming parallel light rays refract and converge to a focal point.
Diverging lens: Incoming parallel light rays refract in such a way that extended rays diverge to a focal point in front of the lens.
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50. Refraction Check Your Neighbor
Which of these occur in raindrops that form
rainbows?
Reflection
Refraction
Dispersion
all of the above
Explain your answer to your neighbor.
D. all of the above
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51. Refraction Check Your Answer
Which of these occur in raindrops that form
rainbows?
Reflection
Refraction
Dispersion
all of the above
D. all of the above
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52. Diffraction
Diffraction is any bending of light by means other than reflection and refraction.
Smaller openings produce greater diffraction (greater bending of the waves at edges).
The amount of diffraction depends on the wavelength of the wave compared to the size of the obstruction that casts the shadow.
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53. Interference Interference is the combined effect of two or more
overlapping waves.
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54. Interference There are two types of interference:
In constructive interference,
the crest of one wave
overlaps the crest of another
wave. The individual effects
add, resulting in a wave of
increased amplitude.
In destructive interference, the crest of one wave overlaps the trough of another. Individual effects are reduced.
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55. Interference CHECK YOUR NEIGHBOR
Interference is a property of
sound.
light.
both sound and light.
neither sound nor light.
Explain your answer to your neighbor.
C. both of these.
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56. Interference CHECK YOUR ANSWER
Interference is a property of
sound.
light.
both sound and light.
neither sound nor light.
Explanation:
See Figure 8.47 for illustrations of both light and sound
interference. Interestingly, the presence of interference tells
a physicist whether something is wavelike or not. All types
of waves can interfere.
C. both of these.
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57. © 2013 Pearson Education, Inc.

58. The Doppler Effect
The Doppler effect is a change in frequency as measured by an observer due to the motion of the source or listener.
The Doppler effect is named after Austrian physicist and mathematician Christian Johann Doppler.
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59. The Doppler Effect Example of the Doppler effect:
The frequency of waves received by an observer increases as a sound source moves toward the observer. The wave frequency decreases as the source moves away.
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60. The Doppler Effect CHECK YOUR NEIGHBOR
When a fire engine approaches you, the
speed of its sound increases.
frequency of its sound increases.
wavelength of its sound increases.
all of the above.
Explain your answer to your neighbor.
B. frequency of sound increases.
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61. The Doppler Effect CHECK YOUR ANSWER
When a fire engine approaches you, the
speed of its sound increases.
frequency of its sound increases.
wavelength of its sound increases.
all of the above.
Comment:
Be sure you distinguish between sound, speed,
and sound frequency.
B. frequency of sound increases.
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62. The Doppler Effect CHECK YOUR NEIGHBOR
The Doppler effect occurs for
sound.
light.
both sound and light.
neither sound nor light.
Explain your answer to your neighbor.
C. both of the above.
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63. The Doppler Effect CHECK YOUR ANSWER
The Doppler effect occurs for
sound.
light.
both sound and light.
neither sound nor light.
Explanation:
As the text states, the Doppler effect occurs for sound
(Figure 8.58) and for light (see the Integrated
Science—Astronomy feature). Astronomers measure the
spin rates of stars by the Doppler effect.
C. both of the above.
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64. The Wave–Particle Duality
In ancient times, Plato, other Greek philosophers, and Isaac Newton thought that light was composed of tiny particles.
100 years after Newton, Thomas Young demonstrated the wave nature of light with interference experiments.
25 years later, the wave view was confirmed by Heinrich Hertz.
Later in 1905, Albert Einstein challenged the wave theory and stated that light was confined in tiny particles of energy called photons. His particle model of light was verified by the photoelectric effect.
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65. The Wave–Particle Duality
Today, light is acknowledged to have both a wave nature and a particlenature—wave–particle duality:
Light reveals itself as a wave or particle depending on how it is being observed.
Light behaves as a wave when it is traveling from a source to a place where it is detected, and light behaves as a stream of photons when it interacts with a detector.
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66. The Wave–Particle Duality
The photoelectric effect
When light shines on certain
metal surfaces, electrons are
ejected from those surfaces.
Ultraviolet and violet light impart
sufficient energy to knock
electrons from those metal
surfaces, but lower-frequency
light does not, even when it is
very bright.
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67. The Wave–Particle Duality CHECK YOUR NEIGHBOR
Why is unexposed black-and-white photographic
film not "exposed" when in red light but is exposed
when in white light?
The red light in a dark room is usually too dim.
Red light has insufficient energy per photon to "expose" the film.
Red light is low-temperature light.
none of the above
Explain your answer to your neighbor.
B. Red light has insufficient energy per photon to "expose" the film.
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68. The Wave–Particle Duality CHECK YOUR ANSWER
Why is unexposed black-and-white photographic
film not "exposed" when in red light but is exposed
when in white light?
The red light in a dark room is usually too dim.
Red light has insufficient energy per photon to "expose" the film.
Red light is low-temperature light.
none of the above
B. Red light has insufficient energy per photon to "expose" the film.
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69. The Wave–Particle Duality
Findings:
The ejection of electrons depends on only the frequency of the light.
The higher the frequency of the light, the greater the kinetic energy of the ejected electrons.
Explanation:
Electrons in the metal are bombarded by "particles of
light"—photons. The energy of each photon is proportional
to its frequency: E  .
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70. The Wave–Particle Duality CHECK YOUR NEIGHBOR
Light travels as a wave and is absorbed as
a wave.
a particle.
both a wave and a particle.
neither a wave nor a particle.
Explain your answer to your neighbor.
B. a particle.
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71. The Wave–Particle Duality CHECK YOUR ANSWER
Light travels as a wave and is absorbed as
a wave.
a particle.
both a wave and a particle.
neither a wave nor a particle.
Explanation:
Light is wavelike as it travels but particle-like when
it encounters a surface.
B. a particle.
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