Waves transfer energy without transferring mass.

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Waves transfer energy without transferring mass.
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Energy Transfer by Waves
Figure 6-1 You can use a domino to knock over
other dominoes in two different ways (a) you can
throw a domino, or (b) you can trigger a wave of
dominoes.
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A wave

• Is a traveling disturbance
• It carries energy from place to place without
  requiring matter to travel across the intervening
  distance.

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0015 Properties of Waves, Sound, and Light 1.
recognize the characteristics of mechanical waves
(e.g., wavelength, amplitude).

• Wavelengths
• Frequency
• Velocity
• Amplitude

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Figure 6-2 A cross section of a wave reveals the
characteristics of wavelength, velocity, and
amplitude. Successive wave crests are numbered 1,
2, 3, and 4. An observer at the position of the
clock records the number of crests that pass by
in a second. This is the frequency, which is
measured in cycles per second, or hertz.
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Two kinds of waves
Figure 6-4 Transverse (a) and longitudinal (b)
waves differ in the motion of the wave relative
to the motion of individual particles.
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Speed of Light Speed of Sound

• 300,000,000 m/s
• 186,000 miles/s

• 331 m/s
• 760 miles/hr

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Relationship among wavelength, frequency, and
velocity

• The velocity of a wave is equal to the length of
  each wave times the number of waves that pass by
  each second.
• Wave velocity (m/s) wavelength (m) x frequency
  (Hz)
• Sample Problem One tube of a wind chime produces
  sound at a frequency of 440 Hz. Assuming the
  speed of sound is 340 m/s, what is the wavelength
  of sound produced by this chime?
• Wavelength velocity / frequency
• 340 meters per second / 440 Hertz 0.77 m

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0015 Properties of Waves, Sound, and Light 2.
demonstrate knowledge of the properties of sound
in everyday phenomena (e.g., echoes, Doppler
effect)
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Echoes

• An echo is a sound wave that bounces back

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The Human Voice

• 2 strong bands of tissue called vocal cords
• --The tighter the vocal cords, faster
• they vibrate, the higher the pitch.
• --Increase volume by
• increasing force of air
• blown between the
• vocal cords.

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Doppler Effect

• If a listener or the source of a sound is moving,
  the listener may hear a pitch that is different
  from the frequency of the source.
• The change in pitch heard when the source of
  sound is moving relative to the listener is the
  Doppler effect.

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Figure 6-9 The Doppler effect occurs whenever a
source of waves is moving relative to the
observer of the waves. (a) Sound waves spread out
from a source in all directions stationary
listeners hear the same pitch. (b) Sound waves
from a moving source seem to increase or decrease
in pitch, depending on whether the sound is
approaching or receding. (c) The Doppler shift
for light waves cause a blueshift for approaching
sources, and a redshift for receding sources.
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How Sound is Produced

• Sound is a form of energy caused by vibrating
  matter.

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How Sounds Travel

• Vibrations push against molecules in the air and
  press them closer together
• Molecules pushed compression
• Molecules spread rarefaction

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Characteristics of Sound

• Intensity the loudness or softness of a
  sound

• Pitch how high or low the sound seems

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Characteristics of Sound

• Pitch - how high or low sound seems
• Intensity - loudness or softness
• Quality - the mix of frequencies that allow us to
  distinguish between different sounds
• Interference waves from two different sources
  come together (constructive or destructive)

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0015 Properties of Waves, Sound, and Light 3.
recognize how the behavior of waves is affected
by the medium through which the waves are
passing.
The speed of sound in air is about 336 meters/sec
or 1100 ft/sec In liquids, the molecules are
closer together and carry the vibrations more
easily and quickly (4X gt). In solids, the
atoms are very close together and carry the
vibrations very easily and quickly (9-15X gt).
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0015 Properties of Waves, Sound, and Light 4.
recognize characteristics of the electromagnetic
spectrum.
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Maxwell, in 1867, proposed that light is an
electromagnetic wave.

• The spectrum of visible light, from red to
  violet, is only an octave or so in the range of
  invisible radiations. There is a whole keyboard
  of information all the way from the longest
  wavelengths of radiowaves (the low notes) to the
  shortest wavelengths of X-rays and beyond (the
  highest notes) (Bronowski, p. 353).

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Electromagnetic waves
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Figure 6-11 The electromagnetic spectrum
includes all kinds of waves that travel at the
speed of light, including radio, microwave,
infrared, visible light, ultraviolet, X-rays, and
gamma rays. Note that sound waves, water waves,
seismic waves, and other kinds of waves that
require matter in order to move travel much
slower than light speed.
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Anatomy of the Electromagnetic Wave

• Electrical and magnetic fields arranged at right
  angles to each other
• Perpendicular to the direction the wave is moving

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The nature of light

• Ø Light is a form of radiant energy given out by
  the Sun and other light producing bodies in the
  form of waves.
• Ø Light is the one part of a group of the em
  spectrum that we can see.
• --Consists of transverse waves, --move up and
  down as they travel forward

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0015 Properties of Waves, Sound, and Light 5.
identify the effect of mirrors, lenses and prisms
on the behavior of light.
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Same Speed across the whole em spectrum!

• Velocity of em waves depends on electrical and
  magnetic interactions, not on the properties of
  the wave itself.

• All em waves move at the speed of light!
• Wavelength x frequency 300,000 km/sor 186,000
  mi/s

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Light travels in straight lines

• Light travels at a speed of 186,000 miles/sec
  (300,000 km/sec)
• (in 8 minutes, light to travels Sun to Earth)
• Thus we see things happen at the exact moment
  they are happening.

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With regard to light, materials are

• Transparent lets light pass through.
• Translucent lets some light pass through but
  reflects some light.
• Opaque reflects most or all of the light.

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Law of Refection

• Ø      angle of incidence is equal to the angle
  of reflection (holds true for all smooth,
  polished surfaces)

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The Plane Mirror

• light striking the mirror passes thru the
  transparent glass, and then almost all the light
  is reflected back by the shiny, opaque silver

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Mirror Convex
Concave
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Refraction of Light lenses

• convex lens
• light rays passing thru a convex lens are bent
  toward the thicker middle

• concave lens
• light rays passing thru a concave lens are bent
  toward the thicker ends

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Spectrum of visible light
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0015 Properties of Waves, Sound, and Light 6.
demonstrate knowledge of the relationship between
the properties of waves and how they are
perceived by humans (e.g. color, pitch).