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CHAPTER 19 Light
19-1
19-2
19-3
19-4
19-5
19-6
19-7
19-8
19-9
19-10
1
What is the electromagnetic spectrum?
Lesson Review
2
What is light?
Lesson Review
3
Light-Years
Enrichment Activity for Lesson 19-2
4
How do light waves travel?
Lesson Review
5
Speed of Light in Different Materials
Enrichment Activity for Lesson 19-3
6
What are sources of light?
Lesson Review
7
Objects and Light
Enrichment Activity for Lesson 19-4
8
What is photosynthesis?
Lesson Review
9
How do lenses refract light?
Lesson Review
10
How do you see?
Lesson Review
11
How do mirrors reflect light?
Lesson Review
12
Telescopes
Enrichment Activity for Lesson 19-8
13
What is color?
Lesson Review
14
How can light be used?
Lesson Review
15
BIG IDEA Integrating Technology: How is light used in the home?
Lesson Review
16
THE
Chapter 19 Key Term Review
17
Chapter 19 Test
18
Chapter 19 Answer Key
20
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Light: CHAPTER 19, page 1
Name
Class
Date
19-1 What is the electromagnetic spectrum?
Lesson Review
Match each description in Column A with the correct term in Column B. Write
the letters of the correct answers in the spaces provided.
Column B
Column A
__________ 1. usually given off during nuclear reactions
a. microwaves
__________ 2. sometimes used to kill bacteria
b. gamma rays
__________ 3. the only part of the electromagnetic spectrum that the
human eye can see
c.
__________ 4. can be used to form images of bones and internal organs
__________ 5. felt as heat
__________ 6. waves with the longest wavelength and lowest frequency
__________ 7. range of electromagnetic waves
__________ 8. often used for wireless communications and microwave
ovens
X-rays
d. ultraviolet rays
e. radio waves
f.
the visible spectrum
g. infrared rays
h. electromagnetic
spectrum
Skill Challenge
Skills: interpreting diagrams, inferring
The diagram below shows a model of the electromagnetic spectrum. Use the
diagram to answer the questions.
1. Name three types of electromagnetic waves that have wavelengths longer than that of visible light.
___________________________________________________________________________________________
2. Which type of wave has the shortest wavelength? ______________________________________________
3. Which color in the visible spectrum has the shortest wavelength? ________________________________
4. Which color in the visible spectrum has the longest wavelength? _________________________________
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Light: CHAPTER 19, page 2
Name
Class
Date
19-2 What is light?
Lesson Review
Complete the following.
1. Light is a form of ____________________________________________________________________ energy.
2. Light is made up of photons, which are ______________________________________________________ .
3. A _____________________________________________ of light is made up of a stream of many photons.
4. Each photon carries a certain amount of ______________________________________________ , although
some photons have more _________________________________________________________ than others.
5. Light travels in ________________________________________________________________________ lines.
6. A ___________________________________ of light shows the direction of a light beam; it will continue
to travel in a ___________________________________________________ unless its direction is changed.
Skill Challenge
Skills: analyzing, organizing
Light can be changed into other forms of energy. Analyze the examples below
and decide what form or forms of energy light is being changed into. Place a
check mark in the correct columns.
LIGHT AND ENERGY CHANGES
Example
Forms of Energy
Heat
Electrical
Mechanical
Chemical
1. A calculator is powered by a solar cell.
2. Plants make food with sunlight, water,
and CO2.
3. A blacktop surface gets warmer when
sunlight strikes it.
4. A scientist invents a solar-powered car.
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Light: CHAPTER 19, page 3
Name
Class
Date
Light-Years
Enrichment Activity for Lesson 19-2
Skills: interpreting tables, calculating
Read the passage. Then, study the table below that shows the distance in lightyears from Earth to several stars. Refer to the table as you answer the questions
that follow. Round your answers to the nearest tenth.
A light-year sounds like a measurement of time, but it is actually a measurement of
distance. A light-year is the distance that light travels in one year. That may sound like a
very long way, and it is. Light travels at a speed of approximately 300,000 km/s. That
means that in one year, light travels approximately 9.5 trillion km.
The light from an object 1 light-year away takes 1 year to reach you. If a person living on
a planet 1 light-year away turned on a light, it would take 1 year for the light to reach Earth.
The stars in the universe are so far from Earth that their light takes many years to reach
Earth. Have you ever thought that when you look at a star, you are seeing light that is many
years old?
DISTANCE FROM STARS TO EARTH
Star
Approximate Distance
(Light-years)
Proxima Centauri
4.3
Sirius
8.6
Vega
26.5
Betelguese
520.0
Polaris
680.0
Rigel
900.0
1. How far in kilometers is Sirius from Earth? ____________________________________________________
2. Sirius is twice as far from Earth as which star? _________________________________________________
3. How far in kilometers is Rigel from Earth? ____________________________________________________
4. From which star—Polaris or Vega—does light take longer to reach Earth? ________________________
5. Suppose that you look at the star Rigel. How long ago did its light start traveling toward you?
___________________________________________________________________________________________
6. Would it be possible for you to see the star Betelgeuse, even if that star had died hundreds of years
ago? Explain your answer. ___________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
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Light: CHAPTER 19, page 4
Name
Class
Date
19-3 How do light waves travel?
Lesson Review
Write true if the statement is true. If the statement is false, change the underlined
term to make the statement true.
____________________ 1. In a transverse wave, the particles of the medium move up and down at
right angles to the direction of wave motion.
____________________ 2. A light wave is a longitudinal wave.
____________________ 3. Light waves need a medium in which to travel.
____________________ 4. A sound wave is a longitudinal wave.
____________________ 5. Sound waves need a medium in which to travel.
____________________ 6. Light waves travel fastest in air.
____________________ 7. The amplitude of light is the distance from the crest or trough of one wave
to the crest or trough of the next wave.
____________________ 8. The frequency of light is about 300,000 km/sec.
____________________ 9. The wavelength is the height of the wave.
____________________ 10. All electromagnetic waves travel at the same speed.
Skill Challenge
Skills: interpreting diagrams, identifying, analyzing
The diagram below shows a wave. Refer to the diagram as you answer the
questions below.
1. What property of the wave is shown by the section labeled C? ___________________________________
2. What property of the wave is shown by the portion of the wave labeled D? _______________________
3. In what direction is the wave traveling? _______________________________________________________
4. In this wave, which way are the particles moving? _____________________________________________
5. Is this wave a transverse wave or a longitudinal wave? How can you tell? ________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
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Light: CHAPTER 19, page 5
Name
Class
Date
Speed of Light in Different Materials
Enrichment Activity for Lesson 19-3
Skills: interpreting tables, analyzing
Light travels at different speeds in different materials. Study the table. Then,
answer the questions.
DISTANCE OF LIGHT IN DIFFERENT MATERIALS
Material
Speed of Light (km/s)
Vacuum
300,000
Air
299,000
Ice
229,000
Water
225,000
Glass
197,000
Diamond
124,000
1. In which material listed does light travel slowest? ______________________________________________
2. In which material does light travel fastest? ____________________________________________________
3. How does the speed of light traveling from outer space change as it approaches Earth? ____________
___________________________________________________________________________________________
4. Do you think the speed of light may be related to the density of a material? If so, in what way?
Explain your answer. _______________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
5. Study the diagram below. Then, explain when you would expect the light to speed up or slow
down as it follows a path through the glass of ice water.
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
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Light: CHAPTER 19, page 6
Name
Class
Date
19-4 What are sources of light?
Lesson Review
Match each term in Column B with its description in Column A. Write the letter
in the space provided.
Column B
Column A
__________ 1. material that transmits light easily
a. translucent
__________ 2. material that blocks light
b. shadow
__________ 3. object that gives off its own light
c. transparent
__________ 4. object that reflects light
d. opaque
__________ 5. material that transmits some light
e. luminous
__________ 6. formed when a material blocks light
f. illuminated
Skill Challenge
Skills: observing, classifying, organizing
Decide whether each material or object listed below is illuminated, luminous,
opaque, translucent, or transparent. Place a check mark in the correct column.
Material/Object
Illuminated
Luminous
Opaque
Translucent
Transparent
1. Plastic food wrap
2. Lighted candle
3. Stained glass
4. Tracing paper
5. Piece of wood
6. Moon
7. Cardboard
8. Sheer fabric
9. Spotlight
10. Orange juice
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Light: CHAPTER 19, page 7
Name
Class
Date
Objects and Light
Enrichment Activity for Lesson 19-4
Skills: analyzing, classifying
Study each of the drawings below. Decide whether the object shown is
illuminated, luminous, opaque, translucent, or transparent. Write your answer in
the space below each picture.
1.
________________________________________
2.
________________________________________
3.
________________________________________
4.
________________________________________
5.
________________________________________
6.
________________________________________
7.
________________________________________
8.
________________________________________
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Light: CHAPTER 19, page 8
Name
Class
Date
19-5 What is photosynthesis?
Lesson Review
Complete the following.
1. In photosynthesis, plants use energy from the Sun to make _____________________________________ .
2. In photosynthesis, light energy is converted into ________________________________________ energy.
3. Sunlight is absorbed mostly by the _________________________________________________ of a plant.
4. The substance in a leaf that absorbs sunlight is called __________________________________________ .
5. This substance absorbs all colors of light except ___________________________________________ light.
6. As the Sun moves across the sky, the leaves of a plant will _____________________________________ .
7. Light energy can be converted to heat energy, __________________________ energy, chemical energy,
or other forms of energy.
8. Plant leaves look green because _____________________________________________________________ .
Skill Challenge
Skills: interpreting diagrams, relating, analyzing
The diagram and equation below show the process of photosynthesis in plants.
Study the diagram and equation. Then, answer the questions.
1. According to the equation, what is needed
in order for photosynthesis to take place?
_______________________________________
2. What products are produced by
photosynthesis? ________________________
_______________________________________
3. How does water enter a plant? How does
it reach the leaf? ________________________
_______________________________________
4. What is a plant’s source of carbon dioxide?
How does carbon dioxide enter the leaf?
_______________________________________
5. How does sunlight enter the leaf of a plant? ___________________________________________________
___________________________________________________________________________________________
6. How is oxygen released by the leaf? __________________________________________________________
___________________________________________________________________________________________
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Light: CHAPTER 19, page 9
Name
Class
Date
19-6 How do lenses refract light?
Lesson Review
Write true if the statement is true. If the statement is false, change the underlined
term to make the statement true. Write your answers in the spaces provided.
____________________ 1. A lens that curves outward is called a concave lens.
____________________ 2. A lens is a transparent material that reflects light.
____________________ 3. Light is bent when it passes from one medium into another at an angle
other than 90°.
____________________ 4. Light that passes through a convex lens is bent outward.
____________________ 5. The point at which light rays are brought together after passing through a
convex lens is called the focal point.
____________________ 6. After light rays pass through a convex lens, they are bent away from the
lens.
____________________ 7. The focal length is the distance between the image and the focal point.
____________________ 8. A real image can be projected onto a screen.
Skill Challenge
Skills: diagramming, identifying
On each diagram below, use colored pencils to draw the path of the light rays as
they pass through the lens. Identify each lens as a concave lens or a convex lens.
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Light: CHAPTER 19, page 10
Name
Class
Date
19-7 How do you see?
Lesson Review
Answer the following questions.
1. What is the cornea? What is its purpose? ______________________________________________________
___________________________________________________________________________________________
2. What is the pupil? __________________________________________________________________________
3. What is the iris? How does it work? __________________________________________________________
___________________________________________________________________________________________
4. What is the relationship between the lens and the retina? _______________________________________
___________________________________________________________________________________________
5. What is an image? __________________________________________________________________________
6. What does the retina do? ____________________________________________________________________
7. What is the purpose of the optic nerve? _______________________________________________________
___________________________________________________________________________________________
8. Where is the upside-down image produced by the lens converted to a right-side-up image?
___________________________________________________________________________________________
Skill Challenge
Skills: identifying, interpreting a diagram
Identify the parts of the eye shown on the diagram below. Use the following
terms: cornea, iris, pupil, lens, retina, and optic nerve.
1.
________________________________
2.
________________________________
3.
________________________________
4.
________________________________
5.
________________________________
6.
________________________________
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Light: CHAPTER 19, page 11
Name
Class
Date
19-8 How do mirrors reflect light?
Lesson Review
Decide whether each description refers to regular reflection or diffuse reflection.
Write R for regular reflection or D for diffuse reflection in the spaces provided.
__________ 1. forms an irregular image
_________
5. equal values for angle of incidence
and angle of reflection
_________
6. occurs when a surface is rough
_________
7. formed by smooth mirrors
_________
8. different angles of reflection when
light strikes a surface
__________ 2. forms a clear image
__________ 3. can produce a distorted image
__________ 4. occurs only when a surface is
smooth and even
Skill Challenge
Skills: interpreting diagrams, inferring
Study the diagram below. Then, answer the questions.
1. In Figure 1, which lines represent the original light rays? Which lines represent reflected rays?
__________________________________________________________________________________________
2. Which set of lines is parallel in Figure 1? _____________________________________________________
3. What are the angles labeled a and b? _________________________________________________________
4. If angle a = 30°, what is the size of angle b? ___________________________________________________
5. If angle a = 30°, what is the size of the other angles formed by the other incident rays? By the other
reflected rays? ____________________________________________________________________________
6. In Figure 2, which lines represent incident rays? Which represent reflected rays? _________________
7. Is either set of lines parallel? If so, which set or sets? ___________________________________________
8. What type of reflection is shown in Figure 1? In Figure 2? ______________________________________
9. According to the diagrams, what happens to the original parallel rays in each kind of reflection?
__________________________________________________________________________________________
__________________________________________________________________________________________
10. What conclusion can you draw about the angles at which light is reflected in each kind of
reflection? ________________________________________________________________________________
__________________________________________________________________________________________
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Light: CHAPTER 19, page 12
Name
Class
Date
Telescopes
Enrichment Activity for Lesson 19-8
Skills: analyzing, inferring, comparing
The following passage describes two types of telescopes. Read the passage.
Then, answer the questions.
Light telescopes are instruments used to make distant objects appear closer. There are
two kinds of light telescopes: refracting telescopes and reflecting telescopes. A refracting
telescope has two convex lenses. The lenses are called the objective lens and the eyepiece
lens. The objective lens focuses the light entering it. The objective lens is located at one
end of a tube. This lens forms a real, upside-down image.
The eyepiece lens is located at the opposite end of the tube. This is the lens you look
through. The eyepiece lens acts like a magnifying glass. It makes the real image formed
by the objective lens larger. The eyepiece lens forms an enlarged, virtual image.
A reflecting telescope does not have an objective lens. This kind of telescope uses a
concave mirror instead of a lens to focus light. The mirror is located at one end of a tube.
Light enters the tube at the other end, travels the length of the tube, and strikes the
concave mirror. The concave mirror forms a real image. A small, flat mirror then reflects
the image to an eyepiece lens on the side of the tube. As in the refracting telescope, the
eyepiece lens enlarges the image.
1. What are the two main parts of a refracting telescope? __________________________________________
2. What is the purpose of each of these parts? ____________________________________________________
___________________________________________________________________________________________
3. What are the three main parts of a reflecting telescope? _________________________________________
___________________________________________________________________________________________
4. What is the function of each of these parts? ____________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
5. In what way are the refracting telescope and reflecting telescope similar? _________________________
___________________________________________________________________________________________
6. In what ways are the refracting telescope and reflecting telescope different? _______________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
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Light: CHAPTER 19, page 13
Name
Class
Date
19-9 What is color?
Lesson Review
Explain how the terms in each pair are related.
1. prism, light _______________________________________________________________________________
2. colors, visible spectrum ____________________________________________________________________
3. wavelength, color _________________________________________________________________________
4. red, wavelength ___________________________________________________________________________
5. violet, wavelength _________________________________________________________________________
6. prism, refract _____________________________________________________________________________
7. absorbs, color _____________________________________________________________________________
8. color, reflects _____________________________________________________________________________
9. black, absorb ______________________________________________________________________________
10. reflect, white ______________________________________________________________________________
Skill Challenge
Skills: observing, analyzing, organizing
In the table below, list ten objects that you see around you. Based on the color of
each object, decide what color light the object absorbs and what color light the
object reflects. Organize the information by completing the table. The first
example is done for you.
COLORS OF OBJECTS
Object
1. Telephone
Color
Color(s) Absorbed
Color(s) Reflected
black
all colors
none
2.
3.
4.
5.
6.
7.
8.
9.
10.
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Light: CHAPTER 19, page 14
Name
Class
Date
19-10 How can light be used?
Lesson Review
Write true if the statement is true. If the statement is false, change the underlined
term to make the statement true. Write your answers in the spaces provided.
____________________ 1. Optical fibers can be used for cutting, welding, and drilling.
____________________ 2. The use of optical fibers is called fiber optics.
____________________ 3. Laser light is made up of many wavelengths of light.
____________________ 4. Light travels through optical fibers quickly because it refracts repeatedly
within the fiber.
____________________ 5. A beam of laser light cannot travel long distances in a straight line.
____________________ 6. White light is made up of many wavelengths.
____________________ 7. Doctors can attach cameras to optical fibers.
____________________ 8. Total internal reflection exists when light is repeatedly reflected within a
given material.
Skill Challenge
Skills: organizing, identifying
In the space below, construct a table that lists five familiar objects that either use
or are made using fiber optics or lasers. Organize the table so that one area lists
fiber optics, while the other lists lasers.
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Light: CHAPTER 19, page 15
Name
THE
Class
Big IDEA
Date
Integrating Technology
Chapter 19 How is light used in the home?
Lesson Review
Refer to the article, call outs, and Figure19-34 on pages 422 and 423 of your text
to answer the following questions.
1. What is one way in which fiber optics can be used in home technologies? _________________________
___________________________________________________________________________________________
2. What kinds of light are used in a speed cook oven? _____________________________________________
___________________________________________________________________________________________
3. How do rooftop solar-heating panels work? ___________________________________________________
___________________________________________________________________________________________
4. What kind of light is used to play CDs? _______________________________________________________
5. What kind of waves do motion detectors pick up? ______________________________________________
Skill Challenge
Skill: inferring
Which kinds of light-based technologies do you think will be found in homes in the future?
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
Science Log Writing Activity
Complete the Science Log on a separate sheet of paper. To complete the Big Idea Online, go to
www.conceptsandchallenges.com. Follow the online instructions.
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Light: CHAPTER 19, page 16
Name
Class
Date
Chapter 19 Key Term Review
PART A Two of the statements below each term are correct. Circle the letters of
the correct statements.
1. chlorophyll
3. lens
a. green substance
a. opaque material
b. found in all organisms
b. bends light
c. found in plants
c. transparent material
2. electromagnetic spectrum
4. eye
a. includes radio waves
a. sense organ
b. includes visible light
b. luminous object
c. includes opaque objects
c. detects light
PART B Match each term in Column B with its definition in Column A. Write the
correct letter in the space provided.
Column B
Column A
__________ 1.
the use of optical fibers
a.
sight
__________ 2.
objects that give off their own light
b.
regular reflection
__________ 3.
material that transmits light easily
c.
light
__________ 4.
reflection that forms an irregular image
d.
illuminated objects
__________ 5.
lens that curves outward
e.
transparent
__________ 6.
image that can be projected on a screen
f.
luminous objects
__________ 7.
reflection that forms a clear image
g.
fiber optics
__________ 8.
material that transmits some light
h.
diffuse reflection
__________ 9.
objects that reflect light
i.
opaque
__________ 10.
material that blocks light
j.
convex lens
__________ 11.
one of the five human senses
k.
laser
__________ 12.
lens that curves inward
l.
translucent
__________ 13.
light made up of only one wavelength
m.
real image
__________ 14.
form of electromagnetic energy made up of streams
of photons
n.
concave lens
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Light: CHAPTER 19, page 17
Name
Class
Date
Chapter 19 Test
Interpreting Diagrams Use the diagrams to answer the following questions.
A
B
C
D
E
F
_________ 1. Which diagram shows a luminous object?
__________ 2. Which diagram shows a concave lens?
__________ 3. Which diagram shows an object that would appear black?
__________ 4. Which diagram shows laser light?
__________ 5. Which diagram shows a convex lens?
__________ 6. Which diagram shows an object that would appear white?
Multiple Choice Write the letter of the term or phrase that best completes
each statement.
__________ 1. A photon is
a. an atom of light.
c. a small bundle of energy.
b. a visible molecule.
d. a charged particle.
__________ 2. Light waves travel fastest in a
a. solid. b. liquid. c. gas. d. vacuum.
__________ 3. An example of an illuminated object is a
a. mirror. b. light bulb. c. campfire. d. flashlight.
__________ 4. The clear, protective layer of the eye is the
a. iris. b. lens. c. cornea. d. pupil.
__________ 5. The color of light is determined by its
a. speed. b. wavelength. c. amplitude.
d. intensity.
__________ 6. In order to make food, plants need
a. heat. b. fertilizer. c. prisms. d. sunlight.
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Light: CHAPTER 19, page 18
Name
Class
Date
Chapter 19 Test (continued)
__________ 7. Electromagnetic waves
a. do not have electrical properties.
c. are made of two transverse waves.
b. do not have magnetic properties.
d. are made of four transverse waves.
__________ 8. In regular reflection, the reflected image will be
a. clear. b. fuzzy. c. distorted. d. upside down.
__________ 9. An image that can be projected onto a screen is a
a. virtual image. b. real image. c. false image.
__________ 10. A concave lens
a. curves inward.
b. curves outward.
d. true image.
c. reflects light.
d. absorbs light.
__________ 11. The waves with the longest wavelength and the lowest frequency are
a. infrared. b. ultraviolet. c. radio waves. d. X-rays.
__________ 12. The waves with the shortest wavelength and the highest frequency are
a. radio waves. b. gamma rays. c. X-rays. d. ultraviolet.
__________ 13. Laser light
a. includes all the colors of light.
c. has waves that are not in step.
b. travels in a curved line.
d. does not spread out like white light.
__________ 14. The height of a wave is called its
a. frequency. b. amplitude. c. wavelength.
d. speed.
__________ 15. An example of an opaque object is a
a. window. b. cardboard box. c. stained glass window.
d. convex lens.
__________ 16. The amount of light that enters the eye is controlled by the
a. iris. b. retina. c. cornea. d. lens.
__________ 17. The color that has the longest wavelength is
a. blue. b. green. c. red. d. orange.
__________ 18. If a beam of light strikes a mirror at a 30° angle, the angle of reflection will be
a. 60°. b. 30°. c. 0°. d. 180°.
Written Response Answer the following questions in complete sentences.
19. EXPLAIN: What is the process of photosynthesis and how does it work? _________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
20. ANALYZE: What is light? What are some of its characteristics? __________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
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Light: CHAPTER 19, page 19
Answer Key
CHAPTER 19: LIGHT
19-1 What is the electromagnetic
spectrum?
Lesson Review
1. b 2. d 3. f 4. c 5. g 6. e 7. h 8. a
Skill Challenge
1. radio waves, microwaves, and infrared rays
2. gamma rays 3. violet 4. red
19-2 What is light?
Lesson Review
1. electromagnetic 2. small bundles of energy
3. beam 4. energy, energy 5. straight 6. ray,
straight line
Skill Challenge
1. Electrical 2. Chemical 3. Heat 4. Heat,
Electrical, and Mechanical
19-2 What is light?
Enrichment Activity: Light Years
1. 81.7 trillion km 2. Proxima Centauri 3. about
8,550 trillion km 4. Polaris 5. 900 years ago 6. Yes,
because the light from this star takes 520 years to
reach Earth; Even if the star had been dead for
hundreds of years, light that left the star 520 years
ago would still be traveling toward Earth.
19-3 How do light waves travel?
Lesson Review
1. true 2. transverse 3. do not need 4. true 5. true
6. a vacuum 7. wavelength 8. speed 9. amplitude
10. true
Skill Challenge
1. wavelength 2. amplitude 3. left to right 4. up
and down 5. transverse, because the particles of the
medium are moving up and down at right angles to
the direction the wave is traveling
19-3 How do light waves travel?
Enrichment Activity: Speed of Light in Different
Materials
1. diamond 2. vacuum 3. It slows down. 4. Yes;
Light probably travels fastest in low-density
materials and slowest in high-density materials
because the materials, listed in the table are listed in
order of increasing density and decreasing speed of
light. 5. The light would slow down a lot as it
enters the glass, speed up when it enters the water,
speed up a little more when it enters the ice cube,
slow down again when it enters the water, slow
down even more when it enters the glass again,
and then, speed up dramatically when it returns to
the air.
19-4 What are sources of light?
Lesson Review
1. c 2. d 3. e 4. f 5. a 6. b
Skill Challenge
1. Transparent 2. Luminous 3. Translucent
4. Translucent 5. Opaque 6. Illuminated
7. Opaque 8. Translucent 9. Luminous
10. Translucent
19-4 What are sources of light?
Enrichment Activity: Objects and Light
1. illuminated 2. luminous 3. transparent
4. translucent 5. opaque 6. illuminated 7. opaque
8. luminous
19-5 What is photosynthesis?
Lesson review
1. food 2. chemical 3. leaves 4. chlorophyll
5. green 6. move to continue facing the Sun
7. electrical 8. chlorophyll in the leaves is green
Skill Challenge
1. carbon dioxide, water, and energy from the Sun
2. sugar and oxygen 3. It enters through roots in the
soil. Then, it travels up the stem to the leaf. 4. The
source of carbon dioxide is the air; carbon dioxide
enters through stomata on the underside of the leaf.
5. It is absorbed by the leaf. 6. through the stomata
on the underside of the leaf
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
(c) by Pearson Education, Inc./Globe Fearon/Pearson Learning Group. All rights reserved.
Light: CHAPTER 19, page 20
Answer Key
19-6 How do lenses refract light?
19-8 How do mirrors reflect light?
Lesson Review
1. convex 2. bends or refracts 3. true 4. inward
5. true 6. concave 7. lens 8. true
Skill Challenge
Check students’ diagrams for accuracy.
Enrichment Activity: Telescopes
1. objective lens and eyepiece lens 2. The objective
lens focuses the light and forms a real image. The
eyepiece lens makes the image larger and changes it
to a virtual image. 3. concave mirror, flat mirror,
and eyepiece lens 4. The concave mirror focuses the
light and forms a real image. The flat mirror reflects
the image to the eyepiece lens. The eyepiece lens
makes the image larger. 5. Both use an eyepiece
lens to make the image larger. 6. The reflecting
telescope uses a concave mirror to focus light, while
the refracting telescope uses a convex lens to focus
light. In the reflecting telescope, a flat mirror reflects
the image to the eyepiece lens, while in the
refracting telescope, the image travels straight down
the tube from the objective lens to the eyepiece lens.
1. convex lens
2. concave lens
19-7 How do you see?
Lesson Review
1. clear layer that covers the front of the eye; protects
the eye by keeping dirt and bacteria away from the
inner parts of the eye 2. opening through which
light enters the eye 3. It is a muscle that controls the
amount of light that enters the eye. It expands or
contracts depending on the amount of light that is
available. 4. Light that enters the eye is focused by
the lens onto the retina. 5. picture that is formed by
the eye 6. It converts the image into electrical
impulses. 7. It provides a path for electrical
impulses from the retina to travel to the brain. 8. in
the brain
Skill Challenge
1. optic nerve 2. retina 3. cornea 4. lens 5. pupil
6. iris
19-8 How do mirrors reflect light?
Lesson Review
1. D 2. R 3. D 4. R 5. R, D 6. D 7. R 8. D
Skill Challenge
1. solid lines; dashed lines 2. Both sets are parallel.
3. angle a = angle of incidence; angle b = angle of
reflection 4. 30° 5. They will all be 30°. 6. solid
lines; dashed lines 7. Only the set of solid lines is
parallel. 8. regular; diffuse 9. In regular reflection,
incident rays are parallel and reflected rays are
parallel. In diffuse reflection, incident rays are
parallel and reflected rays are not parallel.
10. In regular reflection, all light will be reflected at
the same angle. In diffuse reflection, the light will be
reflected at different angles.
19-9 What is color?
Lesson Review
Possible answers: 1. A prism is a triangular piece of
glass that separates white light into a band of colors.
2. The seven colors that make up white light are
called the visible spectrum. 3. The wavelength of
light determines its color. 4. Red light has the
longest wavelength. 5. Violet light has the shortest
wavelength. 6. A prism refracts a beam of light.
7. An object absorbs all colors except the color it
reflects. 8. An object appears the color that it
reflects. 9. Objects that absorb all colors of light
appear black. 10. Objects that reflect all colors of
light appear white.
Skill Challenge
Check students’ tables to make sure that they
understand that the color they see is the one that is
reflected from the object, not the color that is
absorbed by it.
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
(c) by Pearson Education, Inc./Globe Fearon/Pearson Learning Group. All rights reserved.
Light: CHAPTER 19, page 21
Answer Key
19-10 How can light be used?
Lesson Review
1. Lasers 2. true 3. one wavelength 4. reflects
5. can 6. true 7. true 8. true
Skill Challenge
Check students’ tables to make sure that they are
organized logically and that objects listed involve
either lasers or fiber optics. Possible answers:
Lasers: CD player, DVD player, supermarket
scanner, medical devices, and industrial tools
Optical fibers: phone cables, TV cables, computer
networks, and medical devices
The Big Idea
Lesson Review
1. Fiber optics can be used in telephone lines in the
home 2. visible and infrared light 3. convert
sunlight into thermal energy for heating air and
water 4. laser light. 5. infrared waves
Skill Challenge
Possible answers: Fiber-optic cables will probably
play a larger role in receiving not only telephone
calls but computer information and TV signals; solar
heating may become more popular; speed cook
ovens will probably become more popular.
CHAPTER 19: LIGHT
Chapter Test
Interpreting Diagrams
1. C 2. A 3. E 4. D 5. B 6. F
Multiple Choice
1. c 2. d 3. a 4. c 5. b 6. d 7. c 8. a 9. b 10. a
11. c 12. b 13. d 14. b 15. b 16. a 17. c 18. b
Written Response
19. Photosynthesis is the process whereby plants
make food from sunlight, carbon dioxide, and water.
In the process, plants give off oxygen. Chlorophyll,
which is a green substance located mostly in the
leaves, absorbs sunlight and enables photosynthesis
to occur.
20. Light is a form of electromagnetic energy that
sometimes behaves as if it is an electromagnetic
wave, and sometimes behaves as if it is made up of
tiny particles of energy called photons. It is made up
of many wavelengths, and can have varying levels
of energy associated with it. It has a speed of about
300,000 km/s in a vacuum.
CHAPTER 19: LIGHT
Key Term Review
PART A
1. a, c 2. a, b 3. b, c 4. a, c
PART B
1. g 2. f 3. e 4. h 5. j 6. m 7. b 8. l 9. d 10. i
11. a 12. n 13. k 14. c
Concepts and Challenges in Physical Science, Teacher’s Resources CD-ROM
(c) by Pearson Education, Inc./Globe Fearon/Pearson Learning Group. All rights reserved.
Light: CHAPTER 19, page 22