eng - iTunNORM 00000314 00000000 000022F9 00000000 000051A1 00000000 0000600E 00000000 00001B58 00000000
How can you see the back of your head You
can use two mirrors to view a reflection of a
reflection of the back of your head
Real-World ProblemHow many images are seen in two mirrors
Goal Infer how the number of images depends
on the angle between two mirrors
Materialsplane mirrors (2) protractor
masking tape paper clip
Safety Precautions
Handle glass mirrors and paper clips carefully
Procedure1 Complete the safety form
2 Lay one mirror on top of the other with the
mirror surfaces together Tape together one
side so they can open and close Use tape to
label them L and R for left and right
3 Open the mirrors and stand them on a sheet
of paper at an angle of 72deg
4 Bend one leg of a paper clip up 90deg and
place it close to the front of the R mirror
5 Count the number of images of the paper
clip you see in the R and L mirrors Record
these numbers in your data table
6 The mirrors create an image of a circle
divided into wedges Record the number
of wedges
7 Hold the R mirror still and slowly move the Lmirror to 90deg Record the numbers of images
of the clip and wedges in the circle Repeat
this time opening the mirrors to 120deg
Conclude and Apply1 Infer the relationship between the number
of wedges and paper clip images
2 Determine the angle that would divide a
circle into six wedges Hypothesize how
many images would be produced Test your
hypothesis
Reflections of Reflections
Demonstrate for younger students the
relationship between the angle of the
mirrors and the number of reflections
338 CHAPTER 11 Sound and Light
Angle
Number of Number
of Mirrors Paper Clip Images
of Wedges R L
72ordm
90ordm
120ordm
Images and Wedges Seen in the Mirrors
Do not write in this book
SECTION 4 Light and Color 339
Why Objects Have ColorWhy do some apples appear red while others look green or
yellow An objectrsquos color depends on the wavelengths of light itreflects Recall that white light is a blend of all colors of visiblelight When a red apple is struck by white light it reflects redlight back to your eyes and absorbs all of the other colorsFigure 24 shows white light striking a green leaf Only the wave-lengths corresponding to green light are reflected to your eyes
Although some objects appear to be black black isnrsquot acolor Black is the absence of visible light Objects that appearblack absorb all colors of light and reflect little or no light backto your eyes White objects appear to be white because theyreflect all colors of visible light
Why does a white object appear white
Colored Filters Wearing tinted glasses changesthe color of almost everything you see If the lensesare yellow the world takes on a golden glow If theyare rose colored everything looks rosy Somethingsimilar would occur if you placed a colored clearplastic sheet over this white page The paper wouldappear to be the same color as the plastic The plasticsheet and the tinted lenses are filters A filter is atransparent material that transmits one or more col-ors of light but absorbs all others The color of a fil-ter is the color of the light that it transmits
Light and Color
Reading Guide
Explain how you see color Describe the difference between
light color and pigment color Predict what happens when dif-
ferent colors are mixed
From traffic lights to great works of
art color is an important part of your
world
Review Vocabulary
retina inner layer of the eye con-
taining cells that convert light
images into electrical signals
New Vocabulary
bull pigment
Figure 24 This leaf absorbs all
wavelengths of visible light except
the wavelengths you see as green
GPS+_339
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eng - iTunNORM 00000305 00000000 00001D5D 00000000 000001A1 00000000 00006110 00000000 0000B2AC 00000000
340 CHAPTER 11 Sound and Light
Looking Through Colored Filters Figure 25 shows howthe color of an object can change when you look at it throughvarious colored filters The cooler looks blue under white lightbecause it reflects only the wavelengths of blue light that strikeit If you look at the cooler through a blue filter the cooler stilllooks blue because the blue filter transmits the reflected bluelight However if you look at the cooler through a red filter thecooler seems black because the red filter blocks the blue lightreflected by the cooler
Why does a blue object appear black whenviewed through a red filter
Seeing ColorAs you approach a busy intersection the color of the traffic
light changes from green to yellow to red On the cross street thecolor changes from red to green At a busy intersection trafficsafety depends on your ability to detect color changes rapidlyHow do you see colors
Light and the Eye In a healthy eye light enters the eyethrough the cornea is focused by the lens and finally forms animage on the retina The retina is made up of two types of cellsthat absorb light as shown in Figure 26 When these cellsabsorb light energy chemical reactions convert light energy intonerve impulses that are transmitted to the brain One type ofcell in the retina called a cone enables you to distinguish colorsand detailed shapes of objects Cones need bright light to gener-ate nerve impulses so they do not operate in dim light As aresult even brightly colored objects might look gray or black indim light
Figure 25 The color of this
cooler changes when viewed
through different color filters
Topic Color BlindnessVisit for Web
links to information about the
causes of color blindness
Activity Research the causes
and types of color blindness Find
out how cones are related to the
ability to distinguish colors
gpesciencecom
GPS+_340
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eng - iTunNORM 000002EC 00000000 000021E7 00000000 00014224 00000000 00006123 00000000 000146D6 00000000
SECTION 4 Light and Color 341
Cones and Rods Your eyes have three types of cones each ofwhich responds to a different range of wavelengths Red conesrespond to mostly red and yellow light Green cones respond tomostly yellow and green light Blue cones respond to mostlyblue and violet light The second type of cell in the retina calleda rod is sensitive to dim light and enables you to see at nightHowever rod cells do not enable you to see colors
Interpreting Color Why does a bananalook yellow The light reflected by the
banana causes the cone cells that are sensitive to red and greenlight to send signals to your brain Your brain could get the samesignal if a mixture of red light and green light reached your eyesThis mixture also would cause your red and green cones torespond and you would see the color yellow As a result lightwith wavelengths corresponding to yellow light and light that isa mixture of red and green light both cause the color yellow tobe seen What happens when you look at a white shirt You seewhite when all wavelengths of visible light enters your eyes Thenall three sets of cones cells send signals to the brain The com-bination of these signals cause you to see the shirt as white
Color Blindness If one or more of your sets of cone cellsdo not function properly you might not be able to distinguishcertain colors This condition is called color blindness orcolor deficiency About eight percent of men and one-halfpercent of women have some form of color blindness Themost common form of color blindness makes it difficult todistinguish between red and green Figure 27 shows an imagethat is used in a test for redndashgreen color blindness Becausered and green are used in traffic signals drivers and pedestri-ans must be able to identify them
Retina
Rod
Cone
Lens
Figure 27 Color blindness is an
inherited sex-linked condition in
which certain sets of cones in the
retina do not function properly
Identify the number that you seein the dots
Figure 26 Light enters the eye
and focuses on the retina The two
types of light-detecting cells
that make up the retina
are called rods and cones
GPS+_341
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eng - iTunNORM 00000340 00000000 00002026 00000000 000155F0 00000000 0000607C 00000000 0000097D 00000000
342 CHAPTER 11 Sound and Light
Mixing ColorsIf you have ever browsed through a paint store you have
probably seen displays where customers can select paint samplesof almost every imaginable color The colors are a result of mix-tures of pigments For example you might have mixed blue andyellow paint to produce green paint A pigment is a coloredmaterial that is used to change the color of other substancesThe color of a pigment results from the different wavelengths oflight that the pigment reflects
Mixing Colored Lights From the glowing orange of a sun-set to the deep blue of a mountain lake all the colors you see canbe made by mixing three colors of light These three colorsmdashred green and bluemdashare the primary colors of light They cor-respond to the three different types of cones in the retina ofyour eye When mixed together in equal amounts they producewhite light as Figure 28 shows Mixing the primary colors indifferent proportions can produce the colors you see
What are the primary colors of light
Paint Pigments If you were to mix equal amounts of redgreen and blue paint would you get white paint If mixing col-ors of paint were like mixing colors of light you would but mix-ing paint is different Paints are made with pigments Pigmentsproduce color as a result of the wavelengths of light they reflectPaint pigments usually are made of chemical compounds suchas titanium oxide a bright white pigment and lead chromatewhich is used for painting yellow lines on highways
Figure 28 White light is pro-
duced when the three primary col-
ors of light are mixed in equal
amounts
Color for PhotosynthesisPlant pigments determinethe wavelengths oflight for photosynthesisLeaves usually look greenbecause of the pigmentchlorophyll Chlorophyllabsorbs most wave-lengths of visible lightexcept green which itreflects However not allplants are green Researchdifferent plant pigmentsto find out how they allowplant species to survive indiverse habitats
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eng - iTunNORM 0000026F 00000000 000023FD 00000000 0000C8EB 00000000 00006149 00000000 000059CB 00000000
SECTION 4 Light and Color 343
Self Check
1 Identity what colors are reflected and what colors are
absorbed if a white light shines on a red shirt
2 Discuss how the primary colors of light differ from the
primary pigment colors
3 Explain why a red apple would appear black if you
looked at it through a blue filter
4 Determine why a white fence appears to be white instead
of multicolored if all colors are present in white light
5 Think Critically Light reflected from an object passes
through a green filter then a red filter and finally a
blue filter What color will the object seem to be
Summary
Why Objects Have Color
bull The color of an object is determined by the
wavelengths of light it reflects
bull The color of a filter is the color of the light the
filter transmits
Seeing Color
bull Rod and cone cells are light-sensitive cells
found in the retina of the human eye
bull Rod cells are sensitive to dim light Cone cells
enable colors to be seen
bull There are three types of cone cells One type
responds to red light another to green light
and another to blue light
Mixing Colors
bull Red green and blue are the primary light
colors Any color of light can be created by
mixing these primary light colors
bull Any pigment color can be formed by mixing
the primary pigment colorsmdashmagenta cyan
and yellow
6 Use Percentages In the human eye there are about
120000000 rods If 90000000 rods trigger at once
what percentage of the total number of rods triggered
7 Convert Units The wavelengths of light are measured
in nanometers (nm) which equals 0000001 mm
Find the wavelength in mm of a light wave that has a
wavelength of 690 nm
Mixing Pigments You can make any pigment color by mixingdifferent amounts of the three primary pigmentsmdashmagenta(bluish red) cyan (greenish blue) and yellow In fact color print-ers use these pigments as well as black ink to make full-colorprints like the pages in this book A primary pigmentrsquos colordepends on the wavelengths of the light that it reflects Actuallypigments both absorb and reflect a range of colors in sending asingle color message to your eye For example in white lightyellow pigment appears yellow because it reflects red and greenlight but absorbs the other wavelengths of visible light The colorof a mixture of two primary pigments is determined by theprimary colors of light that both pigments reflect
Look at Figure 29 The area in the center where the colors alloverlap appears to be black because the three blended primarypigments absorb all the primary colors of light Recall that theprimary colors of light combine to produce white light They arecalled additive colors However when the primary pigment col-ors are combined they absorb all wavelengths of visible light andproduce black Because black results from the absence ofreflected light the primary pigments are called subtractive colors
Figure 29 The three primary
pigment colors appear to be black
when they are mixed
Describe how the primary pigmentcolors are similar to the primary col-ors of light
More Section Review gpesciencecom
GPS+_343
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eng - iTunNORM 000002A9 00000000 00001B2C 00000000 0000E3C1 00000000 00006099 00000000 00004705 00000000
Design Your OwnDesign Your Own
344
Real-World ProblemWhat loud noises do you enjoy and which ones do you find annoying
Most people enjoy a music concert performed by their favorite artist or
the booming displays of fireworks on the Fourth of July Most people
enjoy these loud sounds for short periods of time However certain
other loud noises such as traffic sirens and loud talking can be
annoying Constant annoying noises are called noise pollution What
can be done to reduce noise pollution What types of barriers will best
block out noise pollution
Form a HypothesisBased on your experiences with loud noises form a hypothesis that
predicts the effectiveness of different types of barriers at blocking out
noise pollution
Test Your HypothesisMake a Plan
1 Complete the safety form
2 Decide what type of barriers or materials you will test
3 Describe exactly how you will use these materials
Goals Design an experiment
that tests the effective-
ness of various types of
barriers and materials
for blocking out noise
pollution
Test different types of
materials and barriers
to determine the best
noise blocks
Possible Materialsradio CD player horn
drum or other loud
noise source
shrubs trees concrete
walls brick walls stone
walls wooden fences
parked cars or hanging
laundry
sound meter
meterstick or metric tape
measure
Blocking NfisePollution
4 Identify the controls and variables you will use in your
experiment
5 List the steps you will use and describe each step precisely
6 Prepare a data table in your Science Journal to record your
measurements
7 Organize the steps of your experiment in logical order
Follow Your Plan
1 Ask your teacher to approve your plan and data table before
you start
2 Conduct your experiment as planned
3 Test each barrier two or three times
4 Record the results from each test in your data table in your Science Journal
Analyze Your Data1 Identify the barriers that most effectively reduced noise pollution
2 Identify the barriers that least effectively reduced noise pollution
3 Compare the effective barriers and identify common characteristics that might
explain why they reduced noise pollution
4 Compare the natural barriers you tested with the artificial barriers Which type
of barrier best reduced noise pollution
5 Compare the different types of materials the barriers were made of Which
type of material best reduced noise pollution
Conclude and Apply1 Evaluate whether your results support your hypothesis
2 Predict how your results would differ if you used a louder source of noise such
as a siren
3 Infer from your results how people living near a
busy street could reduce noise pollution
4 Identify major sources of noise pollution in or
near your home How could they be reduced
5 Research how noise pollution can be
unhealthy
LAB 345
Draw a poster illustrating how builders and
landscapers could use certain materials to
better insulate a home or office from excess
noise pollution
346 CHAPTER 11 Sound and Light
A Haiku GardenThe Four Seasons in Poems and Prints
by Stephen Addiss with Fumiko and Akira Yamamoto
Respond to the Reading1 How do the illustrations help the reader
better understand the poems2 What do you think is meant by the
word lingering in the Haiku about springsunlight
3 Linking Science and Writing Writeone haiku about summer and anotherabout fall In one poem use color tohelp you describe the season In theother use light or some property oflight to help describe the season
Research has deter-mined that there is a
connection between color and mood Warmcolors have longer wavelengths and can bemore stimulating Cool colors which haveshorter wavelengths tend to have a calmingor soothing effect on people Light and colorhave long been used as literary symbols Doesthe use of color change what you imaginewhen you read the haiku
UnderstandingLiteratureJapanese Haiku A haiku is a verse thatconsists of three lines and 17 syllables inthe Japanese language The first and thirdlines have five syllables each and themiddle line has seven syllables Why isimagination important in reading haiku
Lingering
in every pool of watermdash
spring sunlightIssa
Withered by winter
the sound of the windmdash
one-color worldBasho
Sound
1 Sound waves are compressional waves thattravel only in matter
2 The speed of sound in a material dependson the type of material as well as itstemperature
3 Loudness depends on a sound waversquos inten-sity Pitch depends on a sound waversquosfrequency
4 Sound waves are used in echolocationsonar and medical imaging
Reflection and Refractionof Light
1 Light can be absorbed reflected or trans-mitted by a material
2 When light waves are reflected theyobey the law of reflectionmdashthe angle ofincidence equals the angle of reflection
3 A light wave is refracted or bent whenit changes speed as it travels at an anglefrom one material to another
Mirrors Lenses andthe Eye
1 Plane mirrors form upright virtual images
2 Images formed by concave mirrors andconvex lenses depend on the location ofthe object relative to the focal point
3 Convex mirrors and concave lenses formvirtual upright images that are smallerthan the object
4 The lens in the human eye changes shape toproduce a sharp image on the retina
Light and Color
1 You see color when light is reflected offobjects and into your eyes
2 Cone cells in the retina are light-sensitivecells that enable you to distinguish colors
3 Red blue and green are the three primarycolors of light and can be mixed to form allother colors
4 The primary pigment colors are magentacyan and yellow
CHAPTER STUDY GUIDE 347
Use the Foldable you made at the beginningof the chapter to help you review sound and light
Interactive Tutor gpesciencecom
Complete each statement with the correctvocabulary word or phrase
1 A change in frequency due to a movingsound source is due to the
2 A flat smooth surface that reflects light andforms an image is a(n)
3 An object is if you can seethrough it clearly
4 The of a material indicates howmuch the speed of light in the materialchanges as light passes through
5 You can change the color of white paint byadding a(n) to it
6 A(n) is a reflecting surface thatcurves outward like the back of a spoon
7 The human perception of the intensity of asound wave is
Choose the word or phrase that best answerseach question
8 Which of the following best describes imageformation by a plane mirrorA) A real image is formed in front of the mirrorB) A real image is formed behind the mirrorC) A virtual image is formed in front of the
mirrorD) A virtual image is formed behind the mirror
9 For a sound with low pitch what else isalso always lowA) amplitude C) wavelengthB) frequency D) wave velocity
10 Which of the following occurs when asound source moves away from youA) The soundrsquos velocity decreasesB) The soundrsquos loudness increasesC) The soundrsquos frequency decreasesD) The soundrsquos frequency increases
Use the table below to answer question 11
11 Based on the data in the table abovewhich of the following would be the speedof sound in air at 30degCA) 3404 ms C) 3494 msB) 3464 ms D) 3534 ms
12 What happens to a light ray travelingparallel to the optical axis of a convexlens that passes through the lensA) It travels parallel to the optical axisB) It passes through the focal pointC) It is bent away from the optical axisD) It forms a virtual image
13 Light waves of which color are bent mostwhen passing through a prismA) blue C) violetB) red D) yellow
14 Which way does a concave lens bend lightA) toward its optical axisB) toward its centerC) toward its edgesD) toward its focal point
Speed of Sound in Air
Temp peed( s)
4
4
4
348 CHAPTER REVIEW
concave lens p 335concave mirror p 332convex lens p 333convex mirror p 333decibel p 322Doppler effect p 323index of refraction p 329intensity p 322
loudness p 322opaque p 327pigment p 342pitch p 323plane mirror p 331translucent p 327transparent p 327
Vocabulary PuzzleMaker gpesciencecom
Use the illustration below to answer question 15
15 Describe how the position of the candlechanged if the image of the candle movedaway from the focal point
16 Apply Acoustic scientists sometimes doresearch in rooms that absorb all soundwaves How could such a room be used tostudy how bats find their food
17 Compare White light passes through atranslucent pane of glass and shines on ashirt Both the translucent glass and theshirt appear green Compare the colors oflight that are absorbed and transmitted bythe glass and the shirt
18 Infer Most mammals including dogs andcats canrsquot see colors Infer how the retinaof a catrsquos eye might be different from theretina of a human eye
19 Determine whether a convex lens could forman image that is enlarged real and upright
20 Infer A car comes to a railroad crossingThe driver hears a trainrsquos whistle and itspitch becomes lower What can beassumed about how the train is moving
21 Compare and contrast the reflection of lightfrom a white wall with a rough surfacewith the reflection of light from a mirror
Optical axis
One
focal
length
Two
focal
lengths
Image
Ray A
Object
Focal
point
Interpreting Graphics 22 Infer why a convex mirror and a concavelens can never produce a real image
23 Predict what color a white shirt wouldappear to be if the light reflected from theshirt passed through a red filter and thenthrough a green filter
24 Explain why windows might begin to rattlewhen an airplane flies overhead
25 Communicate Some people enjoy usingsnowmobiles Others object to the noisethat they make Write a proposal for a pol-icy that seems fair to both groups for theuse of snowmobiles in a state park
CHAPTER REVIEW 349
Use the wave speed equation ν ƒλ to answer
questions 26 and 27
26 Calculate Frequency A sonar pulse has awavelength of 30 cm and a speed inwater of 1500 ms Find its frequency
27 Calculate Wavelength What is the wave-length of a sound wave with a fre-quency of 440 Hz if the speed of soundin air is 340 ms
28 Calculate Angle of Incidence A light ray isreflected from a mirror If the anglebetween the incident ray and thereflected ray is 136deg what is the angleof incidence
29 Determine Object Distance You hold anobject in front of a concave mirror witha focal length of 30 cm If you do notsee a reflected image how far from themirror is the object
30 Calculate Speed The speed of light in avacuum is 300000 kms If the index ofrefraction of water is 133 what is thespeed of light in water
More Chapter Review gpesciencecom
1 Which of the following describes the imageformed by a convex mirror
A enlarged
B inverted
C real
D virtual
Use the figure below to answer question 2
2 Which of the following describes a light raythat passes through the focal point andthen is reflected by the mirror
A It travels parallel to the optical axis
B It forms a real image
C It is reflected back through the focal point
D It forms a virtual image
3 Why does an apple look red
A It reflects red light
B It absorbs red light
C It reflects green and blue light
D It reflects all colors of light except red
Use the figure below to answer questions 4 and 5
4 When the primary colors of light are addedtogether what color appears in area H
A cyan
B magenta
C white
D yellow
5 When the primary colors of light are addedtogether what color appears in area G
A cyan
B magenta
C white
D yellow
6 Which of the following increases as the fre-quency of a sound increases
A amplitude
B intensity
C loudness
D pitch
Red Blue
Green
F
H
G K
Focal pointOptical axis
350 STANDARDIZED TEST PRACTICE
Record your answers on the answer sheet provided by your teacher or on a sheet of paper
STANDARDIZED TEST PRACTICE 351
7 Which of the following parts of the eyeenable you to see colors in bright light
A cone cells
B cornea
C lens
D rod cells
Use the graph below to answer questions 8 and 9
8 Determine how far in centimeters theimage is from the lens when the object is15 centimeters from the lens
9 How far in centimeters is the object fromthe lens when the image distance andobject distance are equal
10 A shirt has stripes that are black and whitein white light If green light shines on thisshirt what colors will the black and whitestripes be
11 If you are on a moving train what hap-pens to the pitch of a crossing bell as youapproach the crossing and then moveaway from the crossing
Use the figure below to answer question 12
12 Describe the vision problem show by thefigure and explain how this vision prob-lem can be corrected
13 Explain why the human eye can see colorsbetter in bright light than in dim light
Image Distance fora Convex Lens
Ima
ge
dis
tan
ce (
cm)
30
25
20
15
10
5 10 15 20 25 30
Object distance (cm)
Standardized Test Practice gpesciencecom
Note Units Read carefully and make note of the units used in
any measurement