5UNIT

UNIT TASK PREvIEw

In the Unit Task you will analyze the advantages and disadvantages, including costs, of the Large Hadron Collider, an important, expensive modern physics experiment. The Unit Task is described in detail on page 666. As you work through the unit, look for Unit Task Bookmarks to see how information in the section relates to the Unit Task.

Revolutions in Modern Physics: Quantum Mechanics and Special Relativity

oVERALL EXPEcTATIons

• analyze, with reference to quantum mechanics and relativity, how the introduction of new conceptual models and theories can infl uence and/or change scientifi c thought and lead to the development of new technologies

• investigate special relativity and quantum mechanics, and solve related problems

• demonstrate an understanding of the evidence that supports the basic concepts of quantum mechanics and Einstein’s theory of special relativity

BIG IDEAs• Light can show particle-like and

wave-like behaviour, and particles can show wave-like behaviour.

• The behaviour of light as a particle and the behaviour of particles as waves can be described mathematically.

• Time is relative to a person’s frame of reference.

• The effects of relativistic motion can be described mathematically.

• New theories can change scientifi c thought and lead to the development of new technologies.

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Focus on STSE

PARTIcLE AccELERATIon AnD THE LARGE HADRon coLLIDERThe Large Hadron Collider (LHC), a particle accelerator at the European laboratory CERN, is the most complicated machine ever built. The LHC has a circumference of 27 km and lies in a tunnel under Switzerland and France. The experimental team involves over 10 000 scientists from over 100 countries. Construction took over a decade, and CERN plans to operate the LHC for the next several years. The amount of data produced in a single year could fill 100 000 DVDs. The final bill for construc-tion and operation will be billions of dollars. This investment has caused controversy, because some people believe there are more pressing problems that the money and effort of scientists could be allocated to solving.

The LHC is able to create two beams of particles that travel in opposite directions inside the machine’s circular accelerator. Each time the particles complete a lap, they gain more and more energy. Eventually, physicists cause the particles to collide, releasing an immense amount of energy that physicists use to try to recreate the conditions just after the big bang. The collider will allow researchers to test our current understanding of fundamental particles and other basic physics concepts. The current model of particle physics explains much of what we see in the universe, but not everything. One predicted fundamental particle, the Higgs boson, has never been detected. Researchers at the LHC expect to observe new physics and possibly signs of the Higgs boson.

Building and operating the LHC requires huge amounts of time, money, and effort, but the machine will produce some incredible results, both for science and for society. The experimental results could change the world, giving physicists profound insight into the true nature of reality itself. Their findings could revolutionize our current understanding of the universe, forcing scientists to no longer support some currently accepted ideas and enter into uncharted territory. The LHC has also already proven that countries from all over the globe can work together to increase our understanding of science. Furthermore, researchers and engineers have developed new technology to turn the original design of the LHC into a real, functioning machine. The new technologies have resulted in many spinoff technologies. Understanding the scientific issues of the LHC requires learning about modern physics, including relativity and the physics of subatomic particles.

Questions 1. Do you think scientific experiments will continue to grow in size and cost? What

are the limits?

2. What do you hope scientists will discover with the LHC?

3. Do you think limits should be set on the resources allocated to “pure research”? If so, who should regulate it, and what guidelines should be used? Explain your reasoning.

Focus on STSE 569NEL

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concEPTs• motion problems

• inertial and non-inertial reference frames

• fi eld theory

• interference patterns of light

• standing waves and harmonics

• theory and experimentation

• conservation of energy and momentum

sKILLs• interpreting images and patterns on graphs

• solving for unknowns in algebraic equations

• practising safe laboratory procedures

• designing experiments to test hypotheses

• communicating scientifi c information clearly and accurately

unIT 5 ARE YoU READY?

Concepts Review 1. Achildstandsintheaisleofatrainmovingeastward

at40.0m/s.Forashorttime,thechildrunsforwardinthesamedirectionasthetrainismovingataconstantspeed,covering15min3s. K/U T/I

(a) Calculatethevelocityofthechildrelativetoanobserveronthetrain.

(b) Calculatethevelocityofthechildrelativetoanobserverontheground.

(c) Asecondtrainmoveswestwardataspeedof30.0m/s.Calculatethevelocityofthechildrelativetoanobserveronthesecondtrain.

2. Considereachofthefollowingsituations.Foreachsituation,identifywhetherthepersonisinaninertialreferenceframeoranon-inertialreferenceframe.Explainyourchoices. K/U A

(a) ataxidriveracceleratingawayfromastoplight(b) achildridingaroundtheouteredgeofacarousel(c) aracecardrivertravellingataconstant200km/h

downthestraightsectionofaracetrack(d) adriverbackingstraightoutofagarageataslow

andconstantspeed(e) astudentridingswiftlydownthefirsthillofa

rollercoaster(f) anairplanemaintainingafixeddirectionand

constantvelocity 3. Statethelawofconservationofenergy. K/U

4. (a) Whatiselectromagneticradiation?(b) Givethreeexamplesoftypesofelectromagnetic

radiation.(c) Listthethreecentralpropertiesofelectromagnetic

waves.(d) Atwhatspeeddoelectromagneticwavestravel

throughavacuum? K/U

5. Statethelawofconservationofmomentum. K/U

6. AstudenttriesusingtwowhiteLEDsaslightsourcesinadouble-slitinterferenceexperiment.Unfortunately,thestudentdoesnotseetheexpectedbrightfringes.ExplainwhythetwoLEDsarenotviablelightsourcesforthisexperiment. T/I C

7. Redlaserlightshinesthroughadoubleslitandcreatesequallyspacedbrightfringes2.3cmapartonadistantscreen.Explainwhatwouldhappentothefringespacingif(a) greenlaserlightwereusedinsteadofred(b) theslitsweremovedclosertogether T/I A

8. Anegativelychargedplasticrodisbroughtcloseto,butdoesnottouch,ametalsphere(Figure 1).Explainwhathappensinsidethesphere,andexplainwhyithappens. K/U C

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Figure 1

9. Sciencedevelopsthroughacombinationoftheoryandexperiment. K/U C

(a) ExplaintheconflictbetweenNewtonandHuygensregardingtheirtheoriesoflight.

(b) DescribehowYoung’sdouble-slitexperimentchangedscientificunderstandingoflight.

NEL570 Unit 5 • Revolutions in Modern Physics: Quantum Mechanics and Special Relativity

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10. (a) Whatisadiffractiongrating?(b) Whatinformationcanbeobtainedusinga

diffractiongrating?(c) Listsomeapplicationsofspectroscopy. K/U

11. Explainhowstandingwavesresultwhenwavescreatedatthelooseendofastringreflectoffthefixedend. K/U C

12. Matcheachtermontheleftwiththemostappropriatedescriptionontheright. K/U

(a) hypothesis (i) anexplanationthathasbeentestedandconfirmedasageneralprincipletoexplainanaturalphenomenon

(b) postulate (ii) agenerallyacceptedformalstatementabouttheoccurrenceofanaturalphenomenon

(c) scientifictheory (iii) apredictedanswertoatestablequestion

(d) scientificlaw (iv) astatementassumedtobetruefromwhichatheoryisdeveloped

13. DescribetheBohrmodeloftheatom. K/U

Skills Review14. Usethewaveequationtocalculatethefrequencyof

eachofthewavelengthsbelow. T/I

(a) 640nm(b) 510nm(c) 320nm

15. WhichwavelengthinQuestion14hasthehighestenergy? K/U T/I A

16. Whengasofacertainelementisheatedenoughtoemitlight,thelightshineswithonlycertainwavelengths.UseBohr’satomictheorytointerprettheseresults. K/U

17. A1.2m–longstringfixedatbothendsvibratesat51Hz.Threeantinodesappearonthestringbetweenthefixedends. K/U T/I

(a) Determineinwhatharmonicmodethestringisvibrating.

(b) Calculatethefundamentalfrequency.(c) Predictthefrequencythatwouldcauseseven

antinodestoappearonthefixedstring.18. Yourclassmateisabouttoperformaninvestigation

involvinganelectriccircuit.Writealistofsafetyprecautionsthatyourclassmatemustfollowtoensuretheinvestigationiscompletedsafely. K/U C

19. Solveforxineachofthefollowingequations. T/I

(a) a1 2 x2

9 3 1016b21

2

5 8.7

(b) 6.3 5 12.4 3 102152x 2 1.7

(c) x 55.23units

Å1 212.0 3 1082 213.0 3 1082 2

20. (a) PlotthedatainTable 1onagraph.

Table 1

x y

0 100.0

20.0 150.0

40.0 200.0

60.0 250.0

(b) Determinethey-intercept.(c) Determinetheslopeoftheline.(d) Derivetheequationthatrepresentsthedata.(e) Whatcanyoudetermineabouttherelationship

betweenxandy? T/I C

21. LookatthegraphinFigure 2. K/U T/I

0

2

4

6

8

0.20 0.4 0.6 0.8 1.0

y

x

Figure 2

(a) Whattypeofcurveisthis?(b) WhathappenstothecurveinFigure2asit

approaches1.0?

CAREER PATHWAYS PREvIEw

Throughout this unit, you will see Career Links. Go to the Nelson Science website to find information about careers related to Revolutions in Modern Physics. On the Chapter Summary page at the end of each chapter, you will find a Career Pathways feature that shows you the educational requirements of the careers. There are also some career-related questions for you to research.

NEL Are You Ready? 571

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