```Chapter 10
Waves
Hmmmm . . .
• What do you think of when you hear the
word wave?
• Write a brief description in your
composition book of what you think a
wave is.
• Then write a short paragraph describing a
time you might have experienced waves.
Section 1: The Nature of
Waves
Objectives (things you just might learn)
• Describe how vibrations in materials set up
wave disturbances that spread away from the
source.
• Distinguish between waves that require a
medium and waves that do not.
• Explain the difference between transverse
and longitudinal waves.
Waves and Energy
• A wave is any disturbance that transmits
energy through matter or empty space.
• The energy passed along by a wave moves
farther and farther from the source of energy.
• Energy can be carried away from its source by
a wave. However, the material through which
the wave travels does not move with the
energy.
Waves and Energy, continued
• Vibrations and Waves A repetitive, backand-forth motion of an object is called a
vibration.
• Vibrations set up wave disturbances in a
material, and the waves spread away from
the source of vibration.
• A vibrating particle passes its energy to a
nearby particle. In this way, energy is
transmitted through a material.
Waves and Energy, continued
• Energy Transfer Through a Medium Most
waves transfer energy by the vibration of
particles in a medium. A medium is matter
through which a wave can travel.
• These are called “mechanical waves.”
• Sound waves, water waves, and seismic waves
all need a medium through which to travel.
Wave Energy, continued
• Energy Transfer Without a Medium
waves, and X rays are examples of waves
can transfer energy without going through
a medium.
• These waves are electromagnetic waves.
Although electromagnetic waves do not
need a medium, they can go through
matter.
TRANSVERSE WAVES
• Transverse Waves are waves in which the
particles vibrate perpendicularly to the
direction the wave is traveling.
• Transverse waves are made up of crests and
troughs.
• Water waves, waves on a rope, and
electromagnetic waves are examples of
transverse waves.
• http://www.acs.psu.edu/drussell/Demos/wave
s/wavemotion.html
Crests and Troughs of Transverse Waves
• Transverse waves have alternating high points
and low points.
• The high point of a wave is a crest.
• The low point of a wave is a trough.
COMPRESSION WAVES
• Compression Waves are waves in which the
particles vibrate back and forth along the path
that the waves moves.
• Compression waves are also known as
longitudinal waves.
• Compression/longitudinal waves are made up of
compressions and rarefactions.
• Waves on a spring are longitudinal waves.
• http://www.acs.psu.edu/drussell/Demos/waves/wavemotion.html
Rarefactions and Compressions of
Longitudinal/Compression Waves
• Longitudinal waves do not have crests and
troughs.
• The region where the particles of matter are
crowded together as the wave of energy
moves through is called a compression.
• The region where the particles are spread out
as the wave moves through is called a
rarefaction.
• http://www.absorblearning.com/media/attachm
ent.action?quick=14w&att=2933
SOUND WAVES
• Sound Waves are longitudinal waves. Sound
waves travel by compressions and
rarefactions of air particles, as shown below.
SURFACE WAVES
• Surface Waves: Combinations of Waves A
transverse waves and a longitudinal wave can
combine to form a surface wave.
• Surface waves look like transverse waves, but
the particles of the medium move in circles
rather than up and down.
SEISMIC WAVES
• Seismic waves are caused by earthquakes.
• Energy is released when crust breaks.
• Seismic waves occur as both transverse and
compressional waves.
• Primary waves are compressional and travel
fastest. They can travel through solids and
liquids.
• Secondary waves are transverse and travel
more slowly due to the way they move. They
cannot travel through liquids—like Earth’s liquid
outer core.
• Surface waves (Love and Rayleigh) are both
transverse and compressional. They move in all
directions and cause the most damage.
Section 2: Wave Properties
Hmmmmm . . .
Draw a longitudinal wave and a transverse
wave in your composition book. Label the
parts of each wave.
Objectives: What you should learn . . .
• Identify and describe four wave properties.
• Explain how frequency and wavelength are
related to the speed of a wave.
Amplitude
• The amplitude of a wave is the maximum
distance that the particles of a medium
vibrate from their rest position.
• A wave with a large amplitude carries
more energy than a wave with a small
amplitude does.
WAVELENGTH
• A wavelength is the distance between any
point on a wave to an identical point on the next
wave.
• A wave with a shorter wavelength carries more
energy than a wave with a longer wavelength
does.
FREQUENCY
• Frequency is the number of waves produced in a
given amount of time.
• Frequency can be found by counting the number of
crests or troughs that pass a point each second.
• Frequency is usually expressed in hertz (Hz). One
hertz equals one wave per second.
• High frequency means more waves per second.
• Low frequency means fewer waves per second.
• If the amplitudes (wave heights) are equal, highfrequency waves carry more energy than lowfrequency waves.
HERTZ
• A frequency of 1 Hz means that 1 wavelength
passes a point in one second. 5 Hz means that 5
waves pass a point in one second.
• As frequency increases, wavelength decreases. In
other words, the more waves that go by per
second, the distance between them decreases.
WAVE SPEED
• Wave Speed is the speed at which a wave
travels.
• The speed depends on the medium a wave
travels through.
• Waves usually travel faster in liquids and solids
than they do in gases.
• An exception is light waves, which travel through
empty space fastest, and gases next fastest.
• Sounds waves travel faster in a medium if the
temperature is increased.
More on WAVE SPEED
• Wave speed (v) can be calculated using
wavelength () and frequency (f), by using the
wave equation, which is shown below:
vf
(Speed = frequency x wavelength)
WAVE Period
• The amount of time
it takes for one
wavelength to pass
a point is the wave’s
period.
• http://www.lajollasurf.org/nepap.html
How Ocean Waves Work
http://oceanexplorer.noaa.gov/edu/learning/9_ocean_waves/activities/breaking_wa
ves.html
Amplitude of Compressional Waves
• In higher amplitude of a compressional/longitudinal
wave, the particles of a compression are closer,
and particles in the rarefaction are farther apart.
• In lower amplitude, the particles in compression are
farther apart, and rarefaction particles are closer
together
More on Compressional Waves
Animation of above compressional wave:
http://www.passmyexams.co.uk/GCSE/physics/basic-waves-theory.html
Section 3: The Behavior of
Waves
Hmmmmmm…..
Write the symbols v, f, and  in your comp
book. What does each symbol stand for?
How does each symbol relate to the other
two symbols? Draw a diagram if it helps.
Objectives
• Describe reflection, diffraction, and
interference.
• Explain how different media affect wave speed
and cause refraction.
• Compare destructive interference with
constructive interference.
• Describe resonance, and give examples.
Reflection
• Reflection happens when a wave bounces
back after hitting a barrier.
• Light waves reflecting off an object allow you
to see that object. A reflected sound wave is
called an echo.
• Waves are not always reflected when they hit
a barrier. A wave is transmitted through a
substance when it passes through the
substance.
Law of Reflection
• According to the law of reflection, the angle of
incidence is equal to the angle of reflection.
• “Incidence” refers to where the wave comes
in contact with a surface.
• http://www.teachersdomain.org/asset/lsps07_vid_lightreflect/
Refraction
• Refraction is the bending of a
wave as the wave pass from one
medium to another at an angle.
• http://www.teachersdomain.org/asset/rr10_vid_refrac/
• When a wave moves from one
medium to another, the wave’s
speed and wavelength changes.
As a result, the wave bends and
travels in a new direction.
• When light waves travel from air
to water, they slow down and
bend toward the perpendicular
of the surface (normal).
Diffraction
• Diffraction is the bending of
waves around a barrier or
through an opening.
• The amount of diffraction of a
wave depends on its
wavelength and the size of the
barrier or opening the wave
encounters.
Diffraction
• The smaller the wavelength compared to an
obstacle the wave encounters, the less it
diffracts.
• Sound waves have a larger wavelength than
light waves and, therefore, will diffract—or bend
around doors and walls easier than light waves.
• That’s why you can hear around corners, but
do not see light as easily bend around a
corner.
• Diffraction affects your
longer wavelengths
than FM.
• Longer wavelengths
diffract (bend) around objects easier.
• Therefore, AM has a tendency to be able
to travel farther because obstacles do not
get in their way as much.
Interference
• Interference is the result of two or more waves
overlapping.
• Interference of sounds waves through a
water medium.
ldjs&feature=related
Constructive Interference (in-phase)
• Constructive Interference happens with the
crests of one wave overlap with the crests of
another wave or waves. The troughs of the
waves also overlap.
• In other words, the amplitudes (or energy) of
• In sound waves, this increases loudness.
• The result is a new wave that has a larger
amplitude than the original waves had.
Destructive Interference (out-of-phase)
• Destructive interference happens when the
crests of one wave and the troughs of another
wave overlap. The new wave have a smaller
amplitude than the original waves had.
• In other words, the waves subtract from one
another to create a less energetic wave.
• In sound waves, this causes a reduction in
loudness.
• When the waves involved in destructive
interference have the same amplitude and
meet each other at just the right time, the result
is no wave at all (silence for sound waves).
Interference, continued
• Standing Waves are waves that appear to be
standing still. A standing wave only looks as if it is
standing still. Waves are actually going in both
directions.
• In a standing wave, certain parts of the wave are
always at the rest position because of total
destructive interference. Other parts have a large
amplitude because of constructive interference.
Chapter 10
Section 3 Wave Interactions
Interference, continued
• The frequencies at which standing waves form are
called resonant frequencies.
• Resonance happens when an object vibrating at or
near the resonant frequency of a second object
causes the second object to vibrate.
• http://www.science-animations.com/supportfiles/pendulum.swf
• An example of resonance is shown on the next slide.
Chapter 10
Section 3 Wave Interactions
Interference, continued
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/waves/generalwa
vesrev1.shtml
Chapter 10
The Energy of Waves
Concept Mapping
Use the terms below to complete the concept map
on the next slide.
transverse
frequency
waves
longitudinal
wave speed
amplitude
energy
medium
Chapter 10
The Energy of Waves
Concept Mapping, continued
Chapter 10
The Energy of Waves
Concept Mapping, continued
End of Chapter 10 Show
Resources
Chapter 10
Standardized Test Preparation
FCAT
separate sheet of paper.
Chapter 10
Standardized Test Preparation
1. The amount of energy a wave carries depends
partly on the wave’s amplitude and wavelength.
Which of the following waves has the largest
amplitude and the shortest wavelength?
A.
B.
C.
D.
Chapter 10
Standardized Test Preparation
1. The amount of energy a wave carries depends
partly on the wave’s amplitude and wavelength.
Which of the following waves has the largest
amplitude and the shortest wavelength?
A.
B.
C.
D.
Chapter 10
Standardized Test Preparation
2. Ocean waves in deep water often travel in groups
of the same wavelength. The image below
shows a group of waves.
Explain one way to compare the energy of different
waves in the same group.
Chapter 10
Standardized Test Preparation
2. Explain one way to compare the energy of different
waves in the same group.
• Full-credit answers should include the following points:
• The energy carried by a wave is related to its
amplitude and its wavelength.
• In a group of waves that have the same wavelength,
the amplitude of the waves may vary.
• More energy is needed to move water further away
from its resting position.
• Therefore, a wave with a larger amplitude carries
more energy than a wave with a smaller amplitude
carries.
Chapter 10
Standardized Test Preparation
3. Some ocean waves are measured as traveling 45
kilometers (km) in one hour. In two minutes, 15 of
these waves pass an observer on an island. Calculate
the wavelength of these waves in meters (m).
Chapter 10
Standardized Test Preparation
3. Some ocean waves are measured as traveling 45
kilometers (km) in one hour. In two minutes, 15 of
these waves pass an observer on an island. Calculate
the wavelength of these waves in meters (m).
100 m
Chapter 10
Standardized Test Preparation
4. The diagram below shows the use of a black light.
Black lights emit ultraviolet light, which is not visible to
humans. After the energy from a black light is
absorbed by specially designed inks, the energy is reemitted by the inks as visible light.
Chapter 10
Standardized Test Preparation
4. continued
Part A. Identify the forms that energy takes as tif flows
through this system. Describe each conversion of
energy.
Part B. Give two reasons why the energy received by
the eye is less than the energy supplied at the
electrical outlet.
Chapter 10
Standardized Test Preparation
4. continued
Part A. The energy entering the system is electrical energy. This
electrical energy is converted into ultraviolet light and thermal
energy by the black-light bulb. The ultraviolet light is converted
into visible light energy by the special ink. The visible light is
Part B. Reason 1: Energy is lost to the surroundings during every
energy conversion. For example, electrical energy is lost as
thermal energy in the black-light bulb. Reason 2: Only some of the
energy emitted by the black-light bulb reaches the special inks
because the ultraviolet light energy spreads in all directions away
from its source. For the same reason, only some of the visible
light energy emitted by the inks reaches a person’s eye.
Chapter 10
Section 1 The Nature of Waves
Chapter 10
Section 1 The Nature of Waves
Chapter 10
Section 1 The Nature of Waves
```