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Resources
Bellringers
Chapter Presentation
Transparencies
Standardized Test Prep
Visual Concepts
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Chapter 15
Sound and Light
Table of Contents
Section 1 Sound
Section 2 The Nature of Light
Section 3 Reflection and Color
Section 4 Refraction, Lenses, and Prisms
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Chapter 15
Section 1 Sound
Objectives
• Recognize what factors affect the speed of sound.
• Relate loudness and pitch to properties of sound
waves.
• Explain how harmonics and resonance affect the
sound from musical instruments.
• Describe the function of the ear.
• Explain how sonar and ultrasound imaging work.
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Chapter 15
Section 1 Sound
Bellringer
1. Sound must have a medium through which to travel.
Through which medium—solid, liquid, or gas—does
sound travel the fastest? (Hint: Use the kinetic
theory.)
2. How are different musical notes made with a wind
instrument, such as a clarinet?
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Chapter 15
Section 1 Sound
Bellringer, continued
3. On a string instrument, such as a guitar or violin,
how does one string make different musical notes?
4. Using wave theory, explain how making sound with
a wind instrument is essentially the same as making
sound with a string instrument.
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Chapter 15
Section 1 Sound
Properties of Sound
• A sound wave is a longitudinal wave that is caused
by vibrations and that travels through a material
medium
• Sound waves are caused by vibrations, and carry
energy through a medium.
• The speed of sound depends on the medium.
• The speed of sound in a particular medium depends on how
well the particles can transmit the compressions and
rarefactions of sound waves.
• Sound waves travel faster through liquids and solids than
through gases.
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Chapter 15
Section 1 Sound
Properties of Sound, continued
• Speed of Sound in Various Mediums
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Chapter 15
Section 1 Sound
Speed of Sound
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Chapter 15
Section 1 Sound
Properties of Sound, continued
• Loudness is determined by intensity.
• The intensity of a sound wave describes the rate
at which a sound wave transmits energy through a
given area of the medium.
• Intensity depends on the amplitude of the sound
wave as well as your distance from the source of
the waves.
• The greater the intensity of a sound, the louder the
sound will seem.
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Chapter 15
Section 1 Sound
Sound Intensity and Decibel Level
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Chapter 15
Section 1 Sound
Properties of Sound, continued
• Pitch is determined by frequency.
• The pitch is a measure of how high or low a
sound is perceived to be depending on the
frequency of the sound wave.
• A high-pitched sound corresponds to a highfrequency, and a low-pitched sound corresponds
to a low frequency.
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Chapter 15
Section 1 Sound
Pitch
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Chapter 15
Section 1 Sound
Properties of Sound, continued
• Humans hear sound waves in a limited frequency
range.
• Any sound with a frequency below the range of
human hearing is known as an infrasound.
• An infrasound is slow vibrations of frequencies
lower than 20 Hz.
• Any sound with a frequency above human hearing
range is known as an ultrasound.
• An ultrasound is any sound wave with
frequencies higher than 20 000 Hz.
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Chapter 15
Section 1 Sound
Comparing Infrasonic and
Ultrasonic Sounds
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Chapter 15
Section 1 Sound
Musical Instruments
• Musical instruments rely on standing waves.
• Standing waves can exist only at certain
wavelengths on a string.
• The primary standing wave on a vibrating string
has a wavelength that is twice the length of the
string.
• The frequency of this wave is called the
fundamental frequency.
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Chapter 15
Section 1 Sound
Fundamental Frequency
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Chapter 15
Section 1 Sound
Musical Instruments
• Harmonics give every instrument a unique sound.
• Certain whole-number multiples of the
fundamental frequency are called harmonics.
• Every musical instrument has a characteristic
sound quality resulting from the mixture of
harmonics.
• Instruments use resonance to amplify sound.
• Resonance is a phenomenon that occurs when
two objects naturally vibrate at the same
frequency.
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Chapter 15
Section 1 Sound
Resonance (Frequency)
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Chapter 15
Section 1 Sound
Hearing and the Ear
• The human ear is a very sensitive organ that senses
vibrations in the air, amplifies them, and then
transmits signals to the brain.
• Vibrations pass through three regions in the ear.
• Your ear is divided into three regions—outer,
middle, and inner.
• Resonance occurs in the inner ear.
• As waves pass through the cochlea, they resonate with
specific parts of the basilar membrane.
• Hair cells near the part of the membrane that vibrates then
stimulate nerve fibers that send an impulse to the brain.
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Chapter 15
Section 1 Sound
The Ear
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Chapter 15
Section 1 Sound
Ultrasound and Sonar
• Sonar, sound navigation and ranging, is a system
that uses acoustic signals and echo returns to
determine the location of objects or to communicate.
• Sonar is used for underwater location.
• A sonar system determines distance by measuring
the time it takes for sound waves to be reflected back
from a surface.
d = vt
• d is distance
• v is the average speed of the sound waves in water
• t is time
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Chapter 15
Section 1 Sound
Ultrasound and Sonar
• Ultrasound imaging is used in medicine.
• The echoes of very high frequency ultrasound
waves, between 1 million and 15 million Hz, are
used to produce computerized images called
sonograms.
• Some ultrasound waves are reflected at boundaries.
• Some sound waves are reflected when they pass
from one type of material into another.
• How much sound is reflected depends on the
density of the materials at each boundary.
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Chapter 15
Section 1 Sound
Sonar
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Chapter 15
Section 2 The Nature of Light
Objectives
• Recognize that light has both wave and particle
characteristics.
• Relate the energy of light to the frequency of
electromagnetic waves.
• Describe different parts of the electromagnetic
spectrum.
• Explain how electromagnetic waves are used in
communication, medicine, and other areas.
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Chapter 15
Section 2 The Nature of Light
Bellringer
1. Visible light is composed of waves that have several different
wavelengths. What happens to light that passes through a
prism?
2. Why do we see rainbows on rainy days?
3. An airplane can be detected by radar. When radio waves strike
an airplane, they are reflected back to a detector and the
airplane shows up on a radar screen. Explain how stealth
airplanes fly through the air without being detected by radar.
4. Radio waves that carry radio station transmissions and gamma
rays that destroy cancer cells are both electromagnetic waves.
What property makes one wave harmless and the other
destructive?
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Chapter 15
Section 2 The Nature of Light
Waves and Particles
• The two most commonly used models describe light
either as a wave or as a stream of particles.
• Light produces interference patterns like water waves.
• Light can be modeled as a wave.
• This model describes light as transverse waves that
do not require a medium in which to travel.
• Light waves are also called electromagnetic waves
because they consist of changing electric and
magnetic fields.
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Chapter 15
Section 2 The Nature of Light
Waves and Particles, continued
• The wave model of light explains much of the observed
behavior of light.
• Light waves may reflect, refract, or diffract.
• Light waves also interfere with one another.
• The wave model of light cannot explain some
observations.
• When light strikes a piece of metal, electrons may
fly off the metal’s surface.
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Chapter 15
Section 2 The Nature of Light
Waves and Particles, continued
• Light can be modeled as a stream of particles.
• In the particle model of light, the energy of light is
contained in packets called photons.
• A photon is a unit or quantum of light.
• A beam of light is considered to be a stream of
photons.
• Photons do not have mass.
• The energy in a photon is located in a particular
place.
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Chapter 15
Section 2 The Nature of Light
The Dual Nature of Light
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Chapter 15
Section 2 The Nature of Light
Waves and Particles, continued
• The model of light used depends on the situation.
• The energy of light is proportional to frequency.
• The speed of light depends on the medium.
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Chapter 15
Section 2 The Nature of Light
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Chapter 15
Section 2 The Nature of Light
Energy of a Photon
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Chapter 15
Section 2 The Nature of Light
Waves and Particles, continued
• The brightness of light depends on intensity.
• The quantity that measures the amount of light
illuminating a surface is called intensity.
• Intensity is the rate at which energy flows through a
given area of space.
• Like the intensity of sound, the intensity of light from
a light source decreases as the light spreads out in
spherical wave fronts.
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Chapter 15
Section 2 The Nature of Light
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Chapter 15
Section 2 The Nature of Light
The Electromagnetic Spectrum , continued
• The electromagnetic spectrum consists of light at all
possible energies, frequencies, and wavelengths.
• Sunlight contains ultraviolet light.
• The invisible light that lies just beyond violet light
falls into the ultraviolet (UV) portion of the
spectrum.
• X rays and gamma rays are used in medicine.
• X rays have wavelengths less than 10–8 m.
• The highest energy electromagnetic waves are
gamma rays.
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Chapter 15
Section 2 The Nature of Light
Electromagnetic Spectrum
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Chapter 15
Section 2 The Nature of Light
The Electromagnetic Spectrum, continued
• Infrared light can be felt as warmth.
• Infrared (IR) wavelengths are slightly longer than red light.
• Microwaves are used in cooking and communication.
• Microwaves have wavelengths in the range of centimeters.
• Radio waves are used in communications and radar.
• Radio waves have wavelengths that range from tenths of a
meter to millions of meters.
• Air-traffic control towers use radar to determine the
locations of aircraft.
• Radar, radio detection and ranging, is a system that uses
reflected radio waves to determine the velocity and
location of objects.
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Chapter 15
Section 2 The Nature of Light
Electromagnetic Spectrum
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Chapter 15
Section 3 Reflection and Color
Objectives
• Describe how light reflects off smooth and rough
surfaces.
• Explain the law of reflection.
• Show how mirrors form real and virtual images.
• Explain why objects appear to be different colors.
• Describe how colors may be added or subtracted.
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Chapter 15
Section 3 Reflection and Color
Bellringer
1. Mirrors are used in many different ways. Name five
different technological applications for mirrors.
2. What is the purpose of the mirror underneath a
specimen on a microscope?
3. Identify connections between specific colors and the
meanings they convey.
4. Which color of shirt, black or white, would feel the
coolest on a hot, sunny day? Why?
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Chapter 15
Section 3 Reflection and Color
Reflection of Light
• Light can be modeled as a ray.
• A light ray a line in space that matches the
direction of the flow of radiant energy.
• This model is used to describe reflection and
refraction.
• The study of light in cases in which light behaves
like a ray is called geometrical optics.
• Using light rays, one can trace the path of light in
geometrical drawings called ray diagrams.
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Chapter 15
Section 3 Reflection and Color
Reflection
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Chapter 15
Section 3 Reflection and Color
Reflection of Light, continued
• Rough surfaces reflect
light rays in many
directions.
• Such reflection of
light into random
directions is called
diffuse reflection.
• Smooth surfaces reflect
light rays in one
direction
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Chapter 15
Section 3 Reflection and Color
Reflection of Light, continued
• On smooth surfaces, the angle of the light rays
reflecting off the surface is called the angle of
reflection.
• The angle of incidence is the angle of the light rays
striking the surface.
• The law of reflection states that
the angle of incidence equals the angle of
reflection.
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Chapter 15
Section 3 Reflection and Color
• When light hits a smooth surface, the angle of incidence ()
equals the angle of reflection ( ′).
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Chapter 15
Section 3 Reflection and Color
Law of Reflection
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Chapter 15
Section 3 Reflection and Color
Mirrors
• Flat mirrors form virtual
images by reflection.
• A virtual image is an
image that forms at a
location from which
light rays appear to
come but do not
actually come.
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Chapter 15
Section 3 Reflection and Color
Comparing Real and Virtual Images
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Chapter 15
Section 3 Reflection and Color
Mirrors, continued
• Curved mirrors can distort images.
• Because the surface is not flat, the line
perpendicular to the mirror (the normal) points in
different directions for different parts of the mirror.
• Mirrors that bulge out are called convex mirrors.
• Indented mirrors are called concave mirrors.
• Concave mirrors can create real images.
• Concave mirrors are used to focus reflected light.
• A concave mirror can form a virtual image behind
the mirror or a real image in front of the mirror.
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Chapter 15
Section 3 Reflection and Color
Mirrors, continued
• A real image an image of an object formed by light
rays that actually come together at a specific location.
• A real image results when light rays from a single
point of an object are focused onto a single point or
small area.
• Telescopes use curved surfaces to focus light.
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Chapter 15
Section 3 Reflection and Color
Comparing Concave, Convex and Plane
Mirrors
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Chapter 15
Section 3 Reflection and Color
Seeing Colors
• The different wavelengths of visible light correspond to
many of the colors that you perceive.
• Objects have color because they reflect certain
wavelengths.
• White light from the sun actually contains light from
the visible wavelengths of the electromagnetic
spectrum.
• Colors may add or subtract to produce other colors.
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Chapter 15
Section 3 Reflection and Color
Additive primary colors
Red, green, and blue lights can
combine to produce yellow,
magenta, cyan, or white.
Subtractive primary colors
Yellow, magenta, or cyan filters can
combine to produce red, green, blue,
or black.
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Chapter 15
Section 3 Reflection and Color
Additive Color Mixing
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Objectives
• Describe how light is refracted as it passes between
mediums.
• Explain how fiber optics use total internal reflection.
• Explain how converging and diverging lenses work.
• Describe the function of the eye.
• Describe how prisms disperse light and how
rainbows form.
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Bellringer
1. Lenses are used to make objects appear larger or smaller. List at
least five different uses for a lens.
2. Large, curved mirrors are used to prevent shoplifting in retail
stores. Explain why these mirrors are curved instead of flat.
3. A car mirror on the passenger-side door often has a sign that
reads, “Objects in mirror are closer than they appear.” How does
the shape of the mirror necessitate this warning?
4. In a carnival fun house, mirrors distort the way people look by
making them appear extremely tall, short, wide, or thin, for
example. How are these visual images achieved?
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Refraction of Light
• Light waves bend, or refract, when they pass from
one medium to another.
• Light bends when it changes mediums because the
speed of light is different in each medium.
• When light moves from a material in which its
speed is higher to a material in which its speed is
lower, the ray is bent toward the normal.
• If light moves from a material in which its speed is
lower to one in which its speed is higher, the ray is
bent away from the normal.
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Refraction
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Refraction
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Refraction of Light, continued
• Refraction makes objects appear to be in different
positions.
• Refraction in the atmosphere creates mirages.
• A mirage is a virtual image.
• Light can be reflected at the boundary between two
transparent mediums.
• If the angle at which light rays meet the boundary between
two mediums becomes small enough, the rays will be
reflected as if the boundary were a mirror. This angle is
called the critical angle.
• This type of reflection is called total internal reflection.
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Refraction
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Total Internal Reflection
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Refraction of Light, continued
• Total internal reflection is the complete reflection
that takes place within a substance when the angle of
incidence of light striking the surface boundary is less
than the critical angle.
• Fiber optics use total internal reflection.
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Lenses
• Lenses rely on refraction.
• A lens is a transparent object that refracts light
waves such that they converge or diverge to
create an image.
• A converging lens bends light inward.
• A converging lens can create either a virtual
image or a real image.
• A diverging lens bends light outward.
• A diverging lens can only create a virtual
image.
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Converging and Diverging Lenses
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Lenses, continued
• Lenses can magnify images.
• A magnifying glass is an example of a converging
lens.
• Magnification is a change in the size of an image
compared with the size of an object.
• By adjusting the height of the lens, you can focus
the light rays together into a small area, called the
focal point.
• Microscopes and refracting telescopes use multiple
lenses.
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
A compound microscope
uses several lens to
produce a highly
magnified image.
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Lenses, continued
• The eye depends on refraction and lenses.
• Light first enters the eye through a transparent
tissue called the cornea.
• After the cornea, light passes through the pupil.
• Then, light travels through the lens.
• Muscles can adjust the curvature of the lens until
an image is focused on the back layer of the eye,
the retina.
• The retina is composed of tiny structures, called
rods and cones, that are sensitive to light.
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
The Eye
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Parts of the Human Eye
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Human Eyes
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Dispersion and Prisms
• A prism is an optical system that consists of two or
more plane surfaces of a transparent solid at an
angle with each other.
• Different colors of light are refracted differently.
• Light separates into different colors because of
differences in wave speed.
• In the visible spectrum, violet light travels the slowest and
red light travels the fastest.
• In optics, dispersion is the process of separating
a wave (such as white light) of different
frequencies into its individual component waves
(the different colors)
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Chapter 15
Section 4 Refraction, Lenses,
and Prisms
Dispersion of Light
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Chapter 15
Standardized Test Prep
Understanding Concepts
1. Which of these regions of the electromagnetic
spectrum has the highest energy?
A.
B.
C.
D.
gamma rays
Infrared
radio waves
ultraviolet
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Chapter 15
Standardized Test Prep
Understanding Concepts, continued
1. Which of these regions of the electromagnetic
spectrum has the highest energy?
A.
B.
C.
D.
gamma rays
Infrared
radio waves
ultraviolet
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Chapter 15
Standardized Test Prep
Understanding Concepts, continued
2. Why are X-rays used instead of microwaves to make
images of bones inside your body?
F. Microwaves are more hazardous than X-rays
because of their higher energy.
G. Microwaves have a wavelength that is too short
to be absorbed by bone as are X-rays.
H. Microwaves do not have enough intensity to pass
through soft tissues but X-rays do.
I. X-rays have shorter wavelengths so they pass
through soft tissues, but microwaves are
absorbed.
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Chapter 15
Standardized Test Prep
Understanding Concepts, continued
2. Why are X-rays used instead of microwaves to make
images of bones inside your body?
F. Microwaves are more hazardous than X-rays
because of their higher energy.
G. Microwaves have a wavelength that is too short
to be absorbed by bone as are X-rays.
H. Microwaves do not have enough intensity to pass
through soft tissues but X-rays do.
I. X-rays have shorter wavelengths so they pass
through soft tissues, but microwaves are
absorbed.
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Chapter 15
Standardized Test Prep
Understanding Concepts, continued
3. Why can you hear someone standing around the
corner of a building but not see them?
A. Sound waves diffract around the corner, but light
waves do not.
B. Sound waves interfere around the corner, but
light waves do not.
C. Sound waves reflect around the corner, but light
waves do not.
D. Sound waves refract around the corner, but light
waves do not.
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Chapter 15
Standardized Test Prep
Understanding Concepts, continued
3. Why can you hear someone standing around the
corner of a building but not see them?
A. Sound waves diffract around the corner, but light
waves do not.
B. Sound waves interfere around the corner, but
light waves do not.
C. Sound waves reflect around the corner, but light
waves do not.
D. Sound waves refract around the corner, but light
waves do not.
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Chapter 15
Standardized Test Prep
Understanding Concepts, continued
4. In the early 20th century, physicists observed that a
dim blue light can knock electrons off a metal plate
but even a very bright red light cannot. Explain how
this observation led to a model of light that includes
photons.
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Chapter 15
Standardized Test Prep
Understanding Concepts, continued
4. In the early 20th century, physicists observed that a
dim blue light can knock electrons off a metal plate
but even a very bright red light cannot. Explain how
this observation led to a model of light that includes
photons.
Answer: Because the amount of energy depends on
wavelength rather than intensity, the energy must be
contained in small packets, or photons, that can act
as particles.
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Chapter 15
Standardized Test Prep
Reading Skills
Many remote control devices, such as television remotes
and wireless computer keyboards, use infrared light. A
controller sends signal information to a sensor on the
television or computer that responds to radiation of a
particular wavelength. A universal remote control is
designed to send signals at different wavelengths, so
that it can be used with several different appliances,
such as a television and a DVD player.
5. Demonstrate how you can have many different
electronic devices that can be operated with remote
controls in the same room, but each one only
responds to its own control unit.
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Chapter 15
Standardized Test Prep
Reading Skills, continued
5. Demonstrate how you can have many different
electronic devices that can be operated with remote
controls in the same room, but each one only
responds to its own control unit.
Answer: Because infrared light is electromagnetic
radiation, it has the same properties as visible light.
It cannot diffract around a corner, and is blocked or
absorbed when someone stands between the units.
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Chapter 15
Standardized Test Prep
Reading Skills
Many remote control devices, such as television remotes
and wireless computer keyboards, use infrared light. A
controller sends signal information to a sensor on the
television or computer that responds to radiation of a
particular wavelength. A universal remote control is
designed to send signals at different wavelengths, so
that it can be used with several different appliances,
such as a television and a DVD player.
6. Explain why a television remote control can be used
across a room from the television, but it will not work
around a corner or if someone is standing between the
remote control and the television.
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Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 15
Standardized Test Prep
Reading Skills, continued
6. Explain why a television remote control can be used
across a room from the television, but it will not work
around a corner or if someone is standing between
the remote control and the television.
Answer: Because infrared light is electromagnetic
radiation, it has the same properties as visible light.
It cannot diffract around a corner, and is blocked or
absorbed when someone stands between the units.
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 15
Standardized Test Prep
Interpreting Graphics
7. The transmission of light
through an optic fiber, as
illustrated, uses what
process?
F.
G.
H.
I.
diffraction
interference
reflection
refraction
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 15
Standardized Test Prep
Interpreting Graphics
7. The transmission of light
through an optic fiber, as
illustrated, uses what
process?
F.
G.
H.
I.
diffraction
interference
reflection
refraction
Chapter menu
Resources
Copyright © by Holt, Rinehart and Winston. All rights reserved.