quantum theory.pptx

7/25/2019 QUANTUM THEORY.pptx

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QUANTUM THEOR


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QUANTUM THE

Quantum Theory, in physics, description of the particles thmatter and ho! they interact !ith each other and !Quantum theory e$plains in principle ho! to calculatehappen in any e$periment in%ol%in" physical or &iolo"ic

and ho! to understand ho! our !orld !ors# The nametheory) comes from the fact that the theory descri&es theener"y in the uni%erse in terms of sin"le indi%isi&le units ca*sin"ular quantum+# Quantum theory is dierent from class-lassical physics is an appro$imation of the set of rules anin (uantum theory#


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QUANTUM THE

-lassical physics accurately descri&es the &eha%ior of ener"y in the e%eryday uni%erse# .or e$ample, classe$plains the motion of a car acceleratin" or of a &all /yin" air# Quantum theory, on the other hand, can accurately d

&eha%ior of the uni%erse on a much smaller scale, that ofsmaller particles# The rules of classical physics do not &eha%ior of matter and ener"y on this small scale# Quantumore "eneral than classical physics, and in principle, it coto predict the &eha%ior of any physical, chemical, or &iolo"Ho!e%er, e$plainin" the &eha%ior of the e%eryday !orld !

theory is too complicated to &e practical


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QUANTUM THE

Quantum theory not only speci0es ne! rules for desuni%erse &ut also introduces ne! !ays of thinin" a&out ener"y# The tiny particles that (uantum theory descri&es dde0ned locations, speeds, and paths lie o&1ects descri&ed

physics# 2nstead, (uantum theory descri&es positions properties of particles in terms of the chances that the pha%e a certain %alue# .or e$ample, it allo!s scientists to caliely it is that a particle !ill &e in a certain position at a ce


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QUANTUM THE

Quantum description of particles allo!s scientists to undeparticles com&ine to form atoms# Quantum description of ascientists understand the chemical and physical prmolecules, atoms, and su&atomic particles# Quantum theo

scientists to understand the conditions of the early uni%er3un shines, and ho! atoms and molecules detecharacteristics of the material that they mae up# 4ithotheory, scientists could not ha%e de%eloped nuclear eneelectric circuits that pro%ide the &asis for computers#


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QUANTUM THE

Quantum theory descri&es all of the fundamental force"ra%itation5that physicists ha%e found in nature# The fo(uantum theory descri&es are the electrical, the ma"!ea, and the stron"# 6hysicists often refer to these

interactions, &ecause the forces control the !ay particle!ith each other# 2nteractions also aect spontaneous cisolated particles#


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4A7E3 AN8 6ART

One of the striin" dierences &et!een (uantum theclassical physics is that (uantum theory descri&es enmatter &oth as !a%es and as particles# The type ophysicists study most often !ith (uantum theory is li"ht

physics considers li"ht to &e only a !a%e, and it treastrictly as particles# Quantum theory acno!led"es that and matter can &eha%e lie !a%es and lie particles#


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4A7E3 AN8 6ART

2f !a%es tra%elin" do!n the rope hit the stationary end an&ac, lie !ater !a%es &ouncin" a"ainst a !all, t!o !a%rope may meet each other, hittin" the same place on ththe same time# These t!o !a%es !ill interfere, or com&ine

!a%es e$actly line up5that is, if the crests and trou"!a%es line up5the !a%es interfere constructi%ely# This mthe trou"h of the com&ined !a%e is deeper and the crestthan those of the !a%es &efore they com&ined# 2f the t!o !oset &y e$actly half of a !a%elen"th, the trou"h of one !up !ith the crest of the other# This ali"nment creates d

interference5the t!o !a%es cancel each other oumomentar /at s ot a ears on the ro e#


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92:HT A3 A 4A7E AN8 A

6ART2-9E9ie classical physics, (uantum theory sometimes descri&ea !a%e, &ecause li"ht &eha%es lie a !a%e in many situatiis not a %i&ration of a solid su&stance, such as a rope# li"ht !a%e is made up of a %i&ration in the intensity of th

and ma"netic 0elds that surround any electrically char"ed


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6ART2-9E9ie the !a%es mo%in" alon" a rope, li"ht !a%es tra%el ener"y# The amount of ener"y depends on the fre(uency o!a%es; the hi"her the fre(uency, the hi"her the enefre(uency of a li"ht !a%e is also related to the color of the

e$ample, &lue li"ht has a hi"her fre(uency than that of Therefore, a &eam of &lue li"ht has more ener"y than aintense &eam of red li"ht HA3#


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6ART2-9EUnlie classical physics, (uantum theory also descri&esparticle# 3cientists re%ealed this aspect of li"ht &eha%iore$periments performed durin" the early


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6ART2-9E2n ?@s path# Talso aected &y the collision as thou"h it !ere a particle,ener"y and momentum chan"es#


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6ART2-9EMomentum is a (uantity that can &e de0ned for all pali"ht particles, or photons, momentum depends on the frecolor, of the photon, !hich in turn depends on the photonThe ener"y of a photon is e(ual to a constant num6lanc>s constant, times the fre(uency of the photonconstant is named for :erman physicist Ma$ 6lanc,

proposed the relationship &et!een ener"y and fre(uaccepted %alue of 6lanc>s constant is #


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6ART2-9EThe dual nature of li"ht seems puFFlin" &ecause !e e%eryday e$perience !ith !a%eCparticle duality# 4a%es arephenomenaG !e are all familiar !ith !a%es on a &ody of !a %i&ratin" rope# 6articles, too, are e%eryday o&1ects5cars, &uildin"s, and e%en people can &e thou"ht of as pato our senses, there are no e%eryday o&1ects that are &

and particles# 3cientists increasin"ly 0nd that the rules ththe !orld !e see are only appro$imations of the rules tthe unseen !orld of li"ht and su&atomic particles#


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MATTER A3 A 4A7E AN8 A

6ART2-9E2n ?@s constant *h+ di%ided &y the momentum *p+ of the parElectrons, atoms, and all other particles ha%e de ro"lie !amomentum of an o&1ect depends on its speed and mass, so hea%ier an o&1ect is, the lar"er its momentum *p+ !ill &e# e

constant *h+ is an e$tremely tiny num&er, the de ro"lie !a%elen"%isi&le o&1ect is e$ceedin"ly small# 2n fact, the de ro"lie !a%elenmuch lar"er than an atom is smaller than the siFe of one of e$ample, the de ro"lie !a%elen"th of a &ase&all mo%in" at ?L= is ?#? B ?=CDm *D# B ?=CD ft+# The diameter of a hydro"en atomand smallest atom+ is a&out L B ?= C??m *a&out < B ?=C?=ft+, more

trillion times lar"er than the de ro"lie !a%elen"th of the &ase&all!a%elen ths of e%er da o& ects are so tin that the !a%e n


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6ART2-9E3cientists can determine !hether the electrons are &eh!a%es or lie particles &y comparin" the results of e$periments !ith those of similar e$periments perfo%isi&le !a%es and particles# To esta&lish ho! %isi&le !a%in a dou&leCslit apparatus, physicists can replace thsource !ith a de%ice that creates !a%es in a tan of !ate

in the &arrier are a&out as !ide as the !a%elen"th of !a%es# 2n this e$periment, the !a%es spread out spherthe source until they hit the &arrier# The !a%es pass thslits and spread out a"ain, producin" t!o ne! !a%e fcenters as far apart as the slits are# These t!o ne! setinterfere !ith each other as they tra%el to!ard the dete

far end of the tan#


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6ART2-9EThe !a%es interfere constructi%ely in some places *addin"and destructi%ely in others *cancelin" each other out+#intense !a%es5that is, those formed &y the most cointerference5hit the detector at the spot opposite the&et!een the t!o slits# These stron" !a%es form a pea oon the detector# On either side of this pea, the !a%es de

interfere and cancel each other out, creatin" a lo! point i.urther out from these lo! points, the !a%es are !eaeconstructi%ely interfere a"ain and create t!o more intensity, smaller than the lar"e pea in the middle# Ththen drops a"ain as the !a%es destructi%ely interfere# Thof the !a%es forms a symmetrical pattern on the detec

lar"e pea directly across from the midpoint &et!een th


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6ART2-9E4hen physicists perform the dou&leCslit e$periment !iththe detection pattern matches that produced &y the !a%mar&les# These results sho! that electrons do hproperties# Ho!e%er, if scientists run the e$periment usin!hose slits are much !ider than the de ro"lie !a%elenelectrons, the pattern resem&les the one produced &y th

This sho!s that tiny particles such as electrons &eha%e asome circumstances and as particles in others#


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UN-ERTA2NTY 6R2N

efore the de%elopment of (uantum theory, physiciststhat, !ith perfect e(uipment in perfect conditions, meaphysical (uantity as accurately as desired !as possi&lemechanical e(uations sho! that accurate measurement oposition and the momentum of a particle at the samimpossi&le# This rule is called Heisen&er">s uncertaint

after :erman physicist 4erner Heisen&er", !ho deri%eother rules of (uantum theory# The uncertainty principle mas physicists measure a particle>s position !ith more accuracy, the momentum of the particle &ecomes lessprecise, or more and more uncertain, and %ice %ersa#


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UN-ERTA2NTY 6R2N

Heisen&er" formally stated his principle &y descrrelationship &et!een the uncertainty in the measuremparticle>s position and the uncertainty in the measuremmomentum# Heisen&er" said that the uncertainty i*represented &y $+ times the uncertainty in m*represented &y pG+ must &e "reater than a constant num

to 6lanc>s constant *h+ di%ided &y p *p is aappro$imately e(ual to D#?+# Mathematically, the uprinciple can &e !ritten as $ p h K p# This relationsthat as a scientist measures a particle>s position more accurately5so the uncertainty in its position &ecomes %ethe uncertainty in its momentum must &ecome lar"e to co

and mae this e$pression true# 9ie!ise, if the unce


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UN-ERTA2NTY 6R2N

Quantum theory "i%es e$act ans!ers to many (uestions,only "i%e pro&a&ilities for some %alues# A pro&a&illielihood of an ans!er &ein" a certain %alue# 6ro&a&ilirepresented &y a "raph, !ith the hi"hest point on representin" the most liely %alue and the lo!est represleast liely %alue# .or e$ample, the "raph that sho!s the

of 0ndin" the electron of a hydro"en atom at a certaifrom the nucleus loos lie The nucleus of the atom is atthe "raph# The pro&a&ility of 0ndin" the electron %erynucleus is %ery lo!# The pro&a&ility reaches a de0nite peathe spot at !hich the electron is most liely to &e#


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THE QUANTUMThe 0rst "reat achie%ement of (uantum theory !as to eatoms !or# 6hysicists found e$plainin" the structure of!ith classical physics to &e impossi&le# Atoms consist of char"ed electrons &ound to a positi%ely char"ed nunucleus of an atom contains positi%ely char"ed particprotons and may contain neutral particles called neutron

and neutrons are a&out the same siFe &ut are much hea%ier than electrons are# -lassical physics descri&es aatom as an electron or&itin" a proton, much as the MEarth# y the rules of classical physics, the electron has called inertia that maes it !ant to continue tra%elin" inline#


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THE QUANTUMThe attracti%e electrical force of the positi%ely char"o%ercomes this inertia and &ends the electron>s path intmain" it stay in a closed or&it# The classical electroma"netism says that char"ed particles *such as radiate ener"y !hen they &end their paths# 2f classicapplied to the atom, the electron !ould radiate a!ay

ener"y# 2t !ould slo! do!n and its or&it !ould collapsproton !ithin a fraction of a second# Ho!e%er, physicistsatoms can &e sta&le for centuries or lon"er#


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THE QUANTUMQuantum theory "i%es a model of the atom that e$sta&ility# 2t still treats atoms as electrons surroundin" a nthe electrons do not or&it the nucleus lie moons or&itinQuantum mechanics "i%es the location of an electpro&a&ility instead of pinpointin" it at a certain posithou"h the position of an electron is uncertain, (uant

prohi&its the electron from &ein" at some places# The easdescri&e the dierences &et!een the allo!ed and positions of electrons in an atom is to thin of the ele!a%e# The !a%eCparticle duality of (uantum theory allo!to &e descri&ed as !a%es, usin" the electron>s d!a%elen"th#


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THE 8E7E9O6MENT O. QUAN

THEORYThe de%elopment of (uantum theory &e"an !ith :ermaMa$ 6lanc>s proposal in ?@== that matter can emit ener"y only in small, discrete pacets, called (uanta#introduced the particle nature of li"ht# 2n ?@=L :eAmerican physicist Al&ert Einstein used 6lanc>s !or to ephotoelectric eect, in !hich li"ht hittin" a metal maes

emit electrons# ritish physicist Ernest Rutherford pro%ed consisted of electrons &ound to a nucleus in ?@??# 2n ?@physicist Niels ohr proposed that classical mechanicse$plain the structure of the atom and de%eloped a moatom !ith electrons in 0$ed or&its# ohr>s model of the atdicult to apply to all &ut the simplest atoms#


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THEORY2n ?@


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THEORY2n ?@


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THEORY3ince these 0rst &reathrou"hs in (uantum mechanicalphysicists ha%e focused on testin" and re0nin" (uantufurther connectin" the theory to other theories, and 0applications# 2n ?@s special theory of relati%ity, and in dcreated a theory that came to &e no!n as electrodynamics, or QE8# 2n the early ?@L=s apaneseTomona"a 3hin>ichir and American physicists Richardand ulian 3ch!in"er each independently impro%ed thecommunity>s understandin" of QE8 and made it an e$pe

testa&le theory that successfully predicted or e$plained


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THEORY3ince these 0rst &reathrou"hs in (uantum mechanicalphysicists ha%e focused on testin" and re0nin" (uantufurther connectin" the theory to other theories, and 0applications# 2n ?@s special theory of relati%ity, and in dcreated a theory that came to &e no!n as electrodynamics, or QE8# 2n the early ?@L=s apaneseTomona"a 3hin>ichir and American physicists Richardand ulian 3ch!in"er each independently impro%ed thecommunity>s understandin" of QE8 and made it an e$pe

testa&le theory that successfully predicted or e$plained

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