Chapter 12: Waves

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Transcript Chapter 12: Waves

Integrated Science
Unit 4, Chapter 12
Unit Four: Sound and Waves
Chapter 12 Waves
Waves in Motion
Natural Frequency and Resonance
Chapter 12 Learning Goals
Learn the role waves play in our daily lives, including
our effort to communicate.
Learn the parts and shapes of waves.
Model transverse and longitudinal waves and their
characteristics with a stretched string.
Explore the properties of waves (like reflection and
diffraction) with water.
Investigate resonance and harmony using an electronic
Learn how natural frequency and resonance are
involved in making music.
Chapter 12 Vocabulary Terms
circular waves
 continuous harmonics
 constructive interference
 crest hertz
 destructive interference
 diffraction
 fundamental plane
 longitudinal wave
 natural frequency
 refraction
 resonance
 response
 transverse wave
 trough
 standing wave
 wave fronts
 waves
12.1 Waves
Key Question:
How do we make and describe waves?
*Read text section 12.1
AFTER Investigation 12.1
12.1 Waves
If we poke a ball floating on
water, it will bob up and down
(harmonic motion).
The oscillating ball creates a
wave on the water surface.
The first ball can make a
second ball that is farther
away oscillate.
Explain the transfer of energy.
12.1 Why study about waves?
12.1 Evidence of waves
 Anytime
you see a vibration that moves
 Anything
that makes or responds to sound
 Anything
that makes or responds to light
 Anything
that transmits information through the air
(or space) without wires
cell phones, radio, and television.
 Anything
that allows you to “see through” objects
ultrasound, CAT scans, MRI scans, and X rays
12.1 Transverse and Longitudinal
 A transverse
wave has its oscillations
perpendicular to the direction the wave moves.
 A longitudinal
wave has oscillations in the same
direction as the wave moves.
12.1 Frequency, Amplitude and
12.1 Wavelength
12.1 Speed
speed (m/sec)
frequency (cycles/sec)
wavelength (m)
12.2 Graphs of Harmonic Motion
Key Question:
How do waves move and interact with things?
*Read text section 12.2 AFTER Investigation 12.2
12.2 Waves in Motion
 Waves have crests and troughs.
The crest of a wave is sometimes
called a wave front.
The shape of a wave is determined
by its wave front.
12.3 Natural Frequency and Resonance
Key Question:
What is resonance and why
is it important?
*Read text section 12.3
AFTER Investigation 12.3
12.3 Natural Frequency and Resonance
All things in the universe have a natural
frequency, and many things have more than one.
If you know an object’s natural frequency, you
know how it will vibrate.
If you know how an object vibrates, you know
what kinds of waves it will create.
If you want to make specific kinds of waves, you
need to create objects with natural frequencies
that match the waves you want.
12.3 An example of resonance
12.3 Standing Waves and Harmonics