10
Table of Contents
10
Unit 3: Energy On the Move
Chapter 10: Waves
10.1: The Nature of Waves
10.2: Wave Properties
10.3: The Behavior of Waves
The Nature of Waves
10.1
What’s in a wave?
• wave is a repeating disturbance or
movement that transfers energy through
matter or space.
• Examples?
The Nature of Waves
10.1
Waves and Energy
Click image to view movie
The Nature of Waves
10.1
Waves and Energy
• Because it is moving, the falling pebble
has energy.
• As it splashes into the pool, the pebble
transfers some of its energy to nearby
water molecules, causing them to move.
• What you see is energy traveling in the
form of a wave on the surface of the water.
The Nature of Waves
10.1
Waves and Matter
• Imagine you’re in a boat on a lake.
• Approaching
waves bump
against your
boat, but they
don’t carry it
along with them
as they pass.
The Nature of Waves
10.1
Waves and Matter
• The waves don’t even carry the water
along with them. Only the energy carried
by the waves moves forward.
• All waves have this propertythey carry
energy without transporting matter from
place to place.
The Nature of Waves
10.1
Making Waves
• A wave will travel only as long as it has
energy to carry.
The Nature of Waves
10.1
Making Waves
The Nature of Waves
10.1
Making Waves
• It is the up-and-down motion of your hand
that creates the wave.
• Anything that moves up and down or back
and forth in a rhythmic way is vibrating.
• The vibrating movement of your hand at
the end of the rope created the wave. In
fact,
-All waves are produced by something
that vibrates.
The Nature of Waves
10.1
Mechanical Waves
• Medium- matter the waves travel
through is called a The medium can be a
solid, a liquid, or gas
The Nature of Waves
10.1
Mechanical Waves
• mechanical waves- Waves that can travel
only through a medium.
• Not all waves need a medium.
• Light and radio waves, can travel through
space. (No Medium)
• The two types of mechanical waves are
transverse waves and compressional waves.
The Nature of Waves
10.1
Transverse Waves
• transverse wave, Waves move at right
angles to the direction that the wave travels.
(Like water waves)
• For example, a
water wave
travels
horizontally as
the water moves
vertically up and
down.
The Nature of Waves
10.1
Compressional Waves
• compressional wave, waves move the same
direction that the wave travels.
• You can
model
compressional
waves with a
coiled spring
toy.
The Nature of Waves
10.1
Compressional Waves
• Squeeze several coils together at one end
of the spring. Then let go of the coils.
The Nature of Waves
10.1
Compressional Waves
• As the wave moves, it looks as if the whole
spring is moving toward one end.
• The wave carries energy, but not matter,
forward along the spring.
• Compressional
waves also are
called
longitudinal
waves.
The Nature of Waves
10.1
Sound Waves
• Sound waves are compressional waves.
• When a noise is made, such as when a
locker door slams shut and vibrates,
nearby air molecules are pushed together
by the vibrations.
The Nature of Waves
10.1
Sound Waves
• The air molecules are squeezed together like
the coils in a coiled spring toy are when you
make a compressional wave with it.
• The compressions travel through the air to
make a wave.
The Nature of Waves
10.1
Sound in Other Materials
• Sound waves also can travel through other
mediums, such as water and wood.
• When a sound wave reaches your ear, it
causes your eardrum to vibrate.
• Your inner ear then sends signals to your
brain, and your brain interprets the signals
as sound.
The Nature of Waves
10.1
Water Waves
• Ocean waves are formed most often by
wind blowing across the ocean surface.
• The size of the
waves that are
formed depend on
the wind speed, the
distance over which
the wind blows, and
how long the wind
blows.
The Nature of Waves
10.1
Seismic Waves
• Forces in Earth’s crust can cause regions
of the crust to shift, bend, or even break.
• The breaking
crust vibrates,
creating seismic
(SIZE mihk)
waves that carry
energy outward.
The Nature of Waves
10.1
Seismic Waves
• Seismic waves are a combination of
compressional and transverse waves.
They can travel through Earth and along
Earth’s surface.
• The more the
crust moves
during an
earthquake, the
more energy is
released.
Click image to view movie
Section Check
10.1
Question 1
What is a wave?
Answer
A wave is a repeating movement that
transfers energy through matter or space.
Section Check
10.1
Question 2
Which is carried by a water wave?
A.
B.
C.
D.
a boat on the surface
boat anchor submerged 50 m
energy
water molecules
Section Check
10.1
Answer
The answer is C. Waves carry energy
without transporting matter from place to
place.
Section Check
10.1
Question 3
Which type of wave does not need a medium?
A.
B.
C.
D.
electromagnetic
mechanical
ocean
sound
Section Check
10.1
Answer
The answer is A. Electromagnetic waves are
made by vibrating electric charges and can
travel through space where matter is not
present.
Wave Properties
10.2
The Parts of a Wave
• Waves can differ in how much energy they
carry and in how fast they travel.
• Waves also have other characteristics that
make them different from each other.
Wave Properties
10.2
The Parts of a Wave
• crests - Alternating high points
• troughs - Alternating low points
Wave Properties
10.2
The Parts of a Wave
• Parts of a compressional wave
• Compressionregion where
the coils are
close together.
Wave Properties
10.2
The Parts of a Wave
• Rarefaction- region where coils are spread
apart
Wave Properties
10.2
Wavelength
• wavelength is the distance between two of
the same points on a wave
Wave Properties
10.2
Wavelength
Wave Properties
10.2
Wavelength
• The wavelengths of sound waves that you can
hear range from a few centimeters for the
highest-pitched sounds to about 15 m for the
deepest sounds.
Wave Properties
10.2
Frequency and Period
• frequency of a wave is the number of
wavelengths that pass a fixed point
each second.
• transverse waves- number of crests that
pass by a point each second.
• Frequency is expressed in hertz (Hz).
Wave Properties
10.2
Frequency and Period
• Period- amount of time it takes one
wavelength to pass a point.
Wave Properties
10.2
Wavelength is Related to Frequency
• As frequency increases, wavelength decreases.
• If you move the rope
up, down, and back
up in 1 s, the
frequency of the
wave you generate is
1 Hz.
Wave Properties
10.2
Sound and Mediums
• Sound travel faster in liquids and solids than
they do in gases.
• Light waves travel more slowly in liquid and
solids than they do in gases or in empty space.
• Sound waves faster in a material if the
temperature of the material is increased.
Wave Properties
10.2
Calculating Wave Speed
• You can calculate the speed of a wave
represented by v by multiplying its frequency
times its wavelength.
Wave Properties
10.2
Amplitude and Energy
• Amplitude energy carried by a wave.
• The greater the wave’s
amplitude is, the more
energy the wave carries.
Click image to play movie
Wave Properties
10.2
Amplitude of
Compressional Waves
• The closer
the coils are
in a
compression,
the farther
apart they are
in a
rarefaction.
Wave Properties
10.2
Amplitude of Transverse Waves
• Draw Picture
Section Check
10.2
Question 1
If a wave has a high point and a low point, is it
a compressional or transverse wave?
Section Check
10.2
Answer
Transverse
waves have
alternating high
points, called
crests, and low
points, called
troughs.
Section Check
10.2
Question 2
What is the wavelength of a wave?
Section Check
10.2
Answer
A wavelength is
the distance
between one point
on a wave and the
nearest point just
like it.
Section Check
10.2
Question 3
Which of the following refers to the number of
wavelengths that pass a fixed point each
second?
A.
B.
C.
D.
frequency
period
wavelength
wave speed
Section Check
10.2
Answer
The answer is A. Period is a length of time, and
wavelength is a distance.
Your turn….
Section 1 review page 513 1-9
Section 2 review page 523 1-8
The Behavior of Waves
10.3
To Be a Wave
• All waves must- Reflect, Refract, and
Diffract.
The Behavior of Waves
10.3
Reflection
• How does the reflection of
light allow you to see
yourself in the mirror? It
happens in two steps. First,
light strikes your face and
bounces off. Then, the light
reflected off your face
strikes the mirror and is
reflected into your eyes.
• What about Sound
Waves
The Behavior of Waves
10.3
Echoes
• Echo - sound waves hit an object,
they reflect and come back to
you. You hear the sound
multiple times.
The Behavior of Waves
10.3
The Law of Reflection
Draw this Picture:
• The beam striking
the mirror is called
the incident beam.
• The beam that
bounces off the
mirror is called
the reflected
beam.
The Behavior of Waves
10.3
The Law of Reflection
• The line
drawn
perpendicular
to the surface
of the mirror
is called the
normal.
The Behavior of Waves
10.3
The Law of Reflection
• The angle formed
by the incident
beam and the
normal is the angle
of incidence.
• The angle formed
by the reflected
beam and the
normal is the angle
of refection.
The Behavior of Waves
10.3
The Law of Reflection
• law of reflectionThe angle of
incidence is equal
to the angle of
refection.
• All reflected
waves obey this
law.
The Behavior of Waves
10.3
Refraction
• When a wave passes from one
medium to another. It changes
speed and direction. (Example:
from air to water)
• If the wave is traveling at an angle when it
passes from one medium to another, it
changes direction, or bends, as it changes
speed.
The Behavior of Waves
10.3
Refraction
• RefractionBending of a wave
caused by a change
in its speed as it
moves from one
medium to another.
The Behavior of Waves
10.3
Refraction of Light in Water
• Light waves travel slower in water than in
air. This causes light waves to change
direction and bend toward the normal
• When light waves
travel from air to
water, they slow
down and bend
toward the normal.
The Behavior of Waves
10.3
Refraction of Light in Water
• You may have noticed that objects that are
underwater seem closer to the surface than
they really are.
• In the figure, the
light waves
reflected from the
swimmer’s foot are
refracted away
from the normal
and enter your eyes.
The Behavior of Waves
10.3
Refraction of Light in Water
• However, your brain assumes that all
light waves have traveled in a straight
line.
• The light waves that enter your eyes seem
to have come from a foot that was higher
in the water.
The Behavior of Waves
10.3
Diffraction
• When waves strike an object, several things
can happen.
• The waves can bounce off, or be reflected.
• If the object is transparent, light waves can
be refracted as they pass through it.
• Waves also can behave another way when
they strike an object. The waves can bend
around the object.
The Behavior of Waves
10.3
Diffraction
• Diffraction - an object causes a wave to
change direction and bend around it.
• Diffraction and refraction both cause
waves to bend. The difference is that
refraction occurs when waves pass
through an object, while diffraction
occurs when waves pass around an
object.
The Behavior of Waves
10.3
Diffraction
• After they pass
through the
opening, the waves
spread out.
The Behavior of Waves
10.3
Diffraction and Wavelength
• Examples of diffraction?
The Behavior of Waves
10.3
Hearing Around Corners
• Light waves have a much shorter
wavelength. They are hardly diffracted
at all by the door.
The Behavior of Waves
10.3
Diffraction of Radio Waves
• AM radio waves have longer wavelengths
than FM radio waves do. Because of their
longer wavelengths, AM radio waves
diffract around obstacles like buildings
and mountains.
• As a result, AM radio reception is often
better than FM reception around tall
buildings and natural barriers such as hills.
The Behavior of Waves
10.3
Interference
• interference
When two or more
waves overlap and
combine to form a
new wave
The Behavior of Waves
10.3
Constructive Interference
• constructive interference- waves add
together.
The Behavior of Waves
10.3
Constructive Interference
The Behavior of Waves
10.3
Destructive Interference
• destructive interference- waves cancel each
other.
The Behavior of Waves
10.3
Standing Waves
• standing wave - waves equal in wavelength
and amplitude, travel in opposite directions,
and interfere with each other.
The Behavior of Waves
10.3
Standing Waves in Music
• When the string of a violin is played with a
bow, it vibrates and creates standing waves.
• Some
instruments, like
flutes, create
standing waves
in a column of
air.
The Behavior of Waves
10.3
Resonance
• resonance - object is made to vibrate by
absorbing energy at its natural frequency
• If enough energy is absorbed, the object
can vibrate so strongly that it breaks apart.
Section Check
10.3
Question 1
State the law of reflection.
Answer
According to the law of reflection, the angle of
incidence is equal to the angle of reflection.
Section Check
10.3
Question 2
__________ is the bending of a wave caused by
a change in its speed as it moves from one
medium to another.
A.
B.
C.
D.
diffraction
diffusion
refraction
reflection
Section Check
10.3
Answer
The answer is C. The greater the change in
speed is, the more the wave bends.
Section Check
10.3
Question 3
Which is the means by which you can hear
around corners?
A.
B.
C.
D.
diffraction
diffusion
reflection
refraction
Section Check
10.3
Answer
The answer is A. Diffraction occurs when an
object causes a wave to change direction and
bend around it.
Your turn….
• Quiz handout
Table of Contents
11
Unit 3: Energy On the Move
Chapter 11: Motion
11.1: The Nature of Sound
11.2: Properties of Sound
11.3: Music
11.4: Using Sound
The Nature of Sound
11.1
What causes sound?
Every sound is produced by an object that
vibrates.
For example, your friends’ voices are
produced by the vibrations of their vocal
cords, and music from a carousel and
voices from a loudspeaker are produced by
vibrating speakers.
The Nature of Sound
11.1
Sound Waves
Sound waves are compressional waves.
A compressional wave is made up of two
types of
regions
called
compressions
and
rarefactions.
The Nature of Sound
11.1
Sound Waves
When a radio speaker vibrates outward, the
nearby molecules in the air are pushed
together to
form
compressions.
The Nature of Sound
11.1
Sound Waves
When the speaker moves inward, the nearby
molecules in the air have room to
spread out,
and a
rarefaction
forms.
The Nature of Sound
11.1
Sound Waves
As long as the speaker continues to vibrate
back and forth, compressions and
rarefactions
are formed.
The Nature of Sound
11.1
Traveling as a Wave
Compressions and rarefactions collide with
air molecules as energy is transferred.
Compression- Air molecules close together
Rarefaction- Air molecules spread apart
A series of compressions and rarefactions
travel to your ear that we interpret as
sound
The Nature of Sound
11.1
Moving Through Materials
Most sounds you hear travel through air to
reach your ears.
If you’ve ever been swimming underwater
and heard garbled voices, you know that
sound also travels through water.
The Nature of Sound
11.1
Moving Through Materials
Sound waves can travel through any type of
mattersolid, liquid, or gas.
The matter that a wave travels through is
called a medium.
Sound waves cannot travel through empty
space.
The Nature of Sound
11.1
The Speed of Sound in Different
Materials
The speed of a
sound wave
through a medium
depends on the
substance the
medium is made of
and whether it is
solid, liquid, or
gas.
The Nature of Sound
11.1
The Speed of Sound in Different
Materials
Sound travels the
slowest through
gases, faster
through liquids,
fastest through
solids.
The Nature of Sound
11.1
The Speed of Sound in Different
Materials
The denser the
material the the
closer the
molecules are
together which
makes it easier and
faster to transfer
sound
The Nature of Sound
11.1
The Speed of Sound in Different
Materials
Speed of sound
doesn’t depend
on the loudness.
All sounds travel
through a
medium at the
same speed.
The Nature of Sound
11.1
A Model for Transmitting Sound
A line of people passing a bucket is a model
for molecules
transferring
the energy of
a sound
wave.
The Nature of Sound
11.1
A Model for Transmitting Sound
When the people are far away from each
other, like the
molecules in
gas, it takes
longer to
transfer the
bucket of
water from
person to
person.
The Nature of Sound
11.1
A Model for Transmitting Sound
The bucket travels quickly down the line
when the
people stand
close together.
The closer the
particles, the
faster they can
transfer
energy from
particle to
particle.
The Nature of Sound
11.1
Temperature and the Speed of
Sound
As the temperature of a substance increases,
its molecules move faster.
Molecules more likely to collide with each
other increasing sound speed.
Click image to view movie
The Nature of Sound
11.1
Human Hearing
Vocal cords and mouths move in many
different ways to produce various kinds of
compressional waves.
Your ears and brain
work together to turn
the compressional
waves caused by
speech, music, and
other sources into
something that has
meaning.
The Nature of Sound
11.1
Human Hearing
1st Ear gathers the compressional waves.
2nd Ear amplifies the waves.
3rd Waves are converted to nerve impulses
that travel to the brain.
4th Brain decodes and interprets the nerve
impulses.
The Nature of Sound
11.1
Gathering Sound Waves —
The Outer Ear
The Nature of Sound
11.1
Gathering Sound Waves —
The Outer Ear
Outer ear,
Middle ear,
and Inner ear.
The outer ear is
where sound
waves are
gathered.
The Nature of Sound
11.1
Gathering Sound Waves —
The Outer Ear
The eardrum is a tough membrane about 0.1
mm thick.
When incoming
sound waves
vibrate the
eardrum
The Nature of Sound
11.1
Converting Sound
WavesThe Inner Ear
cochlea
filled with
liquid and
contains tiny
hair cells.
Converts sound
to nerve
impulses
Section Check
11.1
Question 1
What type of wave is a sound wave?
Answer
A sound wave is a compressional wave.
Section Check
11.1
Question 2
In which of the following environments
would sound waves not travel?
A.
B.
C.
D.
at altitudes of 10,000 – 15,000 m
in solid aluminum
on the Moon
under water
Section Check
11.1
Answer
The answer is C. Sound waves require a
medium through which to travel. So,
sound waves cannot travel through empty
space.
Section Check
11.1
Question 3
Which region of the ear amplifies sound
waves?
A.
B.
C.
D.
ear drum
inner ear
middle ear
outer ear
Section Check
11.1
Answer
The answer is C. The bones of the middle
ear amplify sound waves.
Properties of Sounds
11.2
Intensity and Loudness
What happens to the sound waves from your
radio when you adjust the volume? The
notes sound the same as when the volume
was higher, but
something
about the
sound
changes.
Properties of Sounds
11.2
Intensity and Loudness
The difference is that quieter sound waves
do not carry as much energy as louder
sound waves do.
Properties of Sounds
11.2
Intensity and Loudness
The amount of energy a wave carries
corresponds to its amplitude.
For a compressional wave, amplitude is
related to the density of the particles in the
compressions and rarefactions.
Properties of Sounds
11.2
Intensity and Loudness
strongly vibrating objects makes sound
waves with tight, dense compressions.
Weak vibrations
make sound waves
with less dense
compressions.
Properties of Sounds
11.2
Intensity and Loudness
The density of particles in the rarefactions
behaves in the opposite way.
It is important to remember that matter is
not transported during the compression
and rarefaction of a compression
waveonly energy is transported.
Matter compresses and expands as the wave
of energy passes through the matter.
Properties of Sounds
11.2
Intensity
Intensity- amount of energy that flows
through a certain area.
Properties of Sounds
11.2
Intensity
Volume Increases = Intensity Increases
Volume decreases = Intensity decreases
Properties of Sounds
11.2
Intensity
Intensity = how far away sound can be
heard.
If you and a friend whisper a conversation,
the sound waves you create have low
intensity and do not travel far.
Properties of Sounds
11.2
Intensity Decreases with Distance
Intensity influences how far a wave will
travel because some of a wave’s energy is
converted to other forms of energy when it
is passed from particle to particle.
low intensity = less distance sound travels.
High intensity = farther distance sound
travels
Properties of Sounds
11.2
Loudness
Loudness is the human perception of sound
intensity.
When sound waves of high intensity reach
your ear, they cause your eardrum to move
back and forth a greater distance than
sound waves of low intensity do.
Properties of Sounds
11.2
Loudness
The bones of the middle ear convert the
increased movement of the eardrum into
increased movement of the hair cells in the
inner ear.
As a result, you hear a loud sound
Properties of Sounds
11.2
A Scale for Loudness
Sound intensity is measured in decibels (dB)
Properties of Sounds
11.2
A Scale for Loudness
Properties of Sounds
11.2
Pitch
If you were to sing a scale, your voice would
start low and become higher with each
note.
Pitch- how high or
low a sound seems
to be.
pitch is related to
the frequency of
the sound waves.
Properties of Sounds
11.2
Frequency and Pitch
High Pitch = High Frequency
Low Pitch = Low frequency
Properties of Sounds
11.2
Frequency and Pitch
This figure shows different notes and their
frequencies.
A healthy human
ear can hear
sound waves
with
frequencies
from about 20
Hz to 20,000
Hz.
Properties of Sounds
11.2
Ultrasonic and Infrasonic Waves
ultrasonic - waves above 20,000 Hz, High
pitched waves humans cannot hear
Properties of Sounds
11.2
Ultrasonic and Infrasonic Waves
Ultrasonic waves are used in medical
diagnosis and
treatment.
They also are
used to
estimate the
size, shape,
and depth of
underwater
objects.
Properties of Sounds
11.2
Ultrasonic and Infrasonic Waves
Infrasonic waves
frequencies
below 20 Hz
too low for most
people to hear.
Properties of Sounds
11.2
Ultrasonic and Infrasonic Waves
These waves
are produced
by sources
that vibrate
slowly, such
as wind,
heavy
machinery,
and
earthquakes.
Properties of Sounds
11.2
The Doppler Effect
Doppler effect- change in pitch or wave
frequency due to a moving wave source
Properties of Sounds
11.2
Moving Sound
As a race car moves, it sends out sound waves
in the form of compressions and
rarefactions.
The
race car creates a compression, labeled
A.
Compression A
moves through
the air toward
the flagger
standing at the
finish line.
Properties of Sounds
11.2
Moving Sound
By the time compression B leaves the race
car, the car has moved forward.
Because the car has moved since the time it
created compression A, compressions A
and B are closer
together than
they would be
if the car had
stayed still.
Properties of Sounds
11.2
Moving Sound
As a result, the flagger hears a higher pitch.
Properties of Sounds
11.2
A Moving Observer
The Doppler effect happens any time the
source of a sound is changing position
compared with the observer.
It occurs no matter whether it is the sound
source or the observer that is moving.
The faster the change in position, the greater
the change in frequency and pitch.
Properties of Sounds
11.2
Using the Doppler Effect
Radar guns use the Doppler effect to
measure the speed of cars.
Weather radar
also uses the
Doppler shift to
show the
movement of
winds in storms,
such as a
tornado.
Section Check
11.2
Question 1
Each unit on the scale for sound intensity
is called a __________.
Section Check
11.2
Answer
The answer is decibel, abbreviated dB.
Section Check
11.2
Question 2
Sound frequencies above 20,000 Hz are
called __________ waves.
A.
B.
C.
D.
infrasonic
infrared
subsonic
ultrasonic
Section Check
11.2
Answer
The answer is D. Subsonic and infrasonic
are waves with frequencies below 20 Hz.
Section Check
11.2
Question 3
Describe the Doppler effect.
Section Check
11.2
Answer
The Doppler effect is the change in pitch
due to a moving wave source. effect.
Using Sound
11.4
Accoustics
When an orchestra stops playing, does it
seem as if the sound of its music lingers
for a couple of seconds?
reverberation The echoing effect produced
by many reflections of sound
During an orchestra performance,
reverberation can ruin the sound of the
music.
Using Sound
11.4
Accoustics
Acoustics- study of sound
Some scientists and engineers specialize
in acoustics to make concert halls and
other theaters pleasant
EXAMPLES!!
Using Sound
11.4
Accoustics
They know that soft,
porous materials can
reduce excess
reverberation, so
they might
recommend that the
walls of concert halls
be lined with carpets
and draperies.
Using Sound
11.4
Echolocation
At night, bats swoop around in darkness
without bumping into anything.
Their senses of sight and smell help them
navigate.
Echolocation is the process of locating
objects by emitting sounds and
interpreting the sound waves that are
reflected back.
Using Sound
11.4
Sonar
Sonar system
that uses
the
reflection
of
underwater
sound
waves to
detect
objects.
Using Sound
11.4
Ultrasound in Medicine
One of the important uses of ultrasonic
waves is in medicine.
Using special
instruments,
medical
professionals
can send
ultrasonic
waves into a
specific part of
a patient’s
Using Sound
11.4
Ultrasound in Medicine
Reflected ultrasonic waves are used to detect
and monitor conditions such as pregnancy,
certain types of heart disease, and cancer.
Using Sound
11.4
Ultrasound Imaging
Like X rays, ultrasound can be used to
produce images of internal structures.
The sound waves reflect off the targeted
organs or tissues, and the reflected waves
are used to produce electrical signals.
A computer program converts these
electrical signals into video images, called
sonograms.
Using Sound
11.4
Treating with Ultrasound
Sometimes small, hard deposits of calcium
compounds or other minerals form in the
kidneys, making kidney stones.
Ultrasonic treatments are commonly used to
break them up.
Using Sound
11.4
Treating with Ultrasound
Bursts of ultrasound create vibrations that
cause the stones to break into small pieces.
These fragments then pass out of the body
with the urine.
Section Check
11.4
Question 1
The process of locating objects by
emitting sounds and interpreting the
sound waves that are reflected back is
called
__________.
A.
acoustics
B. echolocation
C. infrasonic tracking
D. reverberation
Section Check
11.4
Answer
The answer is B. Echolocation is used by
some animals such as bats and dolphins.
Section Check
11.4
Question 2
Which of the following is not a use of
ultrasonic technology in medicine?
A. examination of the gallbladder
B. examination of bones
C. fetal monitoring in utero
D. kidney stone treatment
Section Check
11.4
Answer
The answer is B. Ultrasound is not as
useful as X rays for examining bones,
because hard tissues absorb ultrasonic
waves instead of reflecting them.
Section Check
11.4
Question 3
What is sonar?
Answer
Sonar is a system
that uses the
reflection of
underwater sound
waves to detect
objects.