polarizarea_luminii

7/30/2019 polarizarea_luminii

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Prof. Elena Rducanu, Colegiul Naional Bnean,Timioara

Polarizarealuminii


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Reactualizare

E

B v

Lumina este o undtransversal

ntre modulele celor doivectori exist relaia:

c

EB

c = 3 108

m/s viteza luminii n vid

lumina este o und electromagnetic n care vectorii intensitate a cmpului

electric E i inducia cmpului magnetic B oscileaz n plane perpendicularepe direcia vitezei de propagare v

B


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Experimentul care evideniaz c lumina este und transversalasupra unei oglinzi dielectrice dinsticl neagr P se trimite un fasciculde raze paralele SO sub unghiul deinciden i

fasciculul reflectat OOcade apoi

pe o oglind identic cu prima, A, sub

acelai unghi de inciden, planele deinciden a celor dou oglinzi sunt

paralele, i apoi se reflect dup

direcia OR

S

O

P

A

O

Plan de

inciden

R

Plan deinciden

i

i

se rotete oglinda A n jurul razei

OO, unghiul de inciden i nu seschimb, dar se observ o scdere

a intensitii fasciculului OR

cnd planele de inciden a celor dou oglinzi sunt perpendiculare ntre

ele, se costat c intensitatea fasciculului OR dispare complet.

S

PO O

A

i

i


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S

OP

O

Ai

i

S

P AO O

R

ii

continund rotirea, fasciculul OR

reapare,crescnd continuu nintensitate pn la o valoare maxim

n momentul n care cele dou plane

de inciden au devenit din nouparalele

dac se continu rotirea fasciculul

OR scade din nou n intensitate

pn se anuleaz cnd planele de

inciden devin iari perpendiculareConcluzie:

Intensitatea fasciculului OR este

maxim cnd unghiul dintre planelede inciden ale celor dou oglinzi iavalorile 0i 180i se anuleazcnd planele sunt perpendiculare

Vibraiile vectorului luminos nu pot avea componente n lungul direcieide propagare, deoarece, ntr-un asemenea caz nu se obine anulareacomplet a intensitii fasciculului, deci vibraia luminoas a fasciculului

OO are loc numai n planul perpendicular pe direcia de propagare


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Lumin polarizat, lumin natural

unda care posed anumite direcii privilegiate n care se execut vibraiilesale se numete und polarizat

fenomenul prin care se produc unde polarizate se numete polarizare

oglinda Pcare face ca fasciculul incident SO s devin polarizat prinreflexie se numete

polarizor, iar oglinda Acare analizeaz fasciculul

polarizat se numete analizor

Luminan care vectorul cmp electric E oscileaz ntr-o singur direcie senumete lumin liniar ( total ) polarizat


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prin compunerea a dou unde coerente polarizate liniar, perpendiculare

ntre ele, avnd o diferen de faz ntre ele se obine lumina polarizat

eliptici n caz particularlumina polarizat circular

n timpul propagrii vrful vectorului luminos rezultant descrie o elips,

respectiv un cerc n planul perpendicular pe direcia de propagare.


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pe aceast direcie preferenial intensitatea luminii este maxim, iar pedirecia perpendicular pe ea intensitatea luminii este minim

n lumina natural undele trimise de fiecare atom al sursei sunt polarizateliniar, dar planele de oscilaie sunt orientate n toate direciile, haotic.

Reprezentare

Lumin totalpolarizat Lumin parial

polarizat

Lumin

natural

Gradul de polarizare:

minmax

minmax

II

IIP

P = 0 lumin natural

P = 1 lumin totalpolarizat

Lumina parial polarizat este lumina n care vectorul cmp electric Eoscileaz ntr-o direcie preferenial, dar nu unic, din planul perpendicularpe direcia de propagare

Lumina natural (nepolarizat) este lumina n care vectorul cmp electric Eoscileaz haotic n toate direciile posibile ntr-un plan perpendicular pedirecia de propagare

E


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Polarizarea prin reflexie. Legea lui Brewstero raz de lumin natural aflat n mediul cu indicele de refracie n1 cade

pe suprafaa de separaie a unui alt mediu cu indicele de refracie n2

Luminanatural Lumin total

polarizat

Lumin parialpolarizat

iB

rB

n1

n2

lumina reflectat va fi total polarizat

dac i = iB ( unghi Brewster )

n acest caz raza reflectat i cea

refractat sunt perpendiculare ntre ele

iB + rB = 90n lumina total polarizat oscilaiile

vectorului luminos au loc perpendicularpe planul de inciden

raza refractat este parial polarizat

i are un grad de polarizare mare

n punctul I: n1siniB = n2sinrB = n2sin(90- iB) = n2cosiB

De unde:

1

2

n

ntgiB

legea luiBrewster

Pentru sticl: iB = 57

I


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Animaii - polarizarea


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Birefrigerena

dac mediul dielectric folosit este transparent, o parte din lumina naturalincident conform legilor refraciei este polarizat prin refracie (transmisie)

trimind un fascicul ngust de lumin natural printr-un cristal de spat deIslanda, tiat cu fee plan paralele, se poate obine lumin polarizat prin

dubl refracie

A

A

10153

fenomenul se numete birefrigeren

spatul de Islanda prezint o birefigeren mare i cristalizeaz n sistemul

romboedric cu unghiul ntre muchii de 10153

cristalul prezint o ax de simetrie AA numit ax optic


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SI

A

A

O O

EE

O E

Oglind plan din sticl

la intrarea n cristal,la inciden normal, fasciculul incident SI se desparten dou alte fascicule IO i IE care apoi ies din cristal, sub form de

fascicule paralele cu direcia fasciculului incident, dac faa de intrare a

cristalului este paralel cu cea de ieire.

OOeste n prelungirea razei incidente, respect legile refraciei i se

numete raz ordinar, iar raza IEeste refractat diferit, nu respect legilerefraciei i se numete raz extraordinaranaliznd cele dou fascicule cu ajutorul oglinzii nclinat la incidena

brewsterian, se constat c prin rotirea oglinzii are loc, pe rnd cnd

stingerea, cnd ntrirea fasciculelor reflectate OO i EE demonstrdu-sec fasciculele OO i EE sunt fiecare polarizate liniar n plane perpendiculare

ntre ele


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Primele polariscoape

a fost folosit pentru determinarea unghiuluiBrewster pentru probe lichide sau solide.


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Polariscoape de colecie

Hampden-Sydney College Smithsonian Institution

Miami University College Allegheny


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Colecia Millington / Barnard de la

Muzeul Universitii din Mississippi.

Colecia de la InstitutulSmithsonian.

Universitatea din Glasgow

Muzeul Universitii dinMississippi


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Filtre de polarizareDispozitivele care las s treac doar lumina polarizat se numesc filtre de

polarizareo versiune a acestora sunt polaroiziifabricai dintr-un strat de polimer cumolecule organice lungi, straturile fiind aliniate sub forma unei reele, iar

polimerul este tratat astfel nct moleculele s devin conductoare

la trecerea luminii prin polaroid sunt absorbite anumite direcii de oscilaie

ale vectorului luminos, astfel c la ieirea din polaroid n und rmn doar

direciile de oscilaie neabsorbite

Lumin natural

Lumin polarizat

Polaroid


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Aplicaii practiceFiltrul de polarizare se folosete pentru eliminarea sau cel puin diminuareareflexiilor nedorite la fotografierea, filmarea sau nregistrarea video.

Obiecte aflate n vitrinele magazinelor

Exemple:


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Persoane care poart ochelari

Interiorul automobilelor


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Suprafaa apei

http://www.youtube.com/watch?v=sNWqo58zNQ0&feature=related
http://www.youtube.com/watch?v=sNWqo58zNQ0&feature=relatedhttp://www.youtube.com/watch?v=sNWqo58zNQ0&feature=relatedhttp://www.youtube.com/watch?v=sNWqo58zNQ0&feature=relatedhttp://www.youtube.com/watch?v=sNWqo58zNQ0&feature=related


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Ochelarii cu polaroizi

Utilizai pentru diminuarearadiaiilor deranjante

http://www.youtube.com/watch?v=eqe-tpXrEiU&feature=related

Farurileautovehiculelor
http://www.youtube.com/watch?v=eqe-tpXrEiU&feature=relatedhttp://www.youtube.com/watch?v=eqe-tpXrEiU&feature=relatedhttp://www.youtube.com/watch?v=eqe-tpXrEiU&feature=relatedhttp://www.youtube.com/watch?v=eqe-tpXrEiU&feature=relatedhttp://www.youtube.com/watch?v=eqe-tpXrEiU&feature=relatedhttp://www.youtube.com/watch?v=eqe-tpXrEiU&feature=related


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Ochelari de pescuit polarizati antireflexii

Fr ochelari polarizani

Cu ochelari polarizani

http://www.youtube.com/watch?v=MNbg4Go8NR0&feature=related
http://www.youtube.com/watch?v=MNbg4Go8NR0&feature=relatedhttp://www.youtube.com/watch?v=MNbg4Go8NR0&feature=relatedhttp://www.youtube.com/watch?v=MNbg4Go8NR0&feature=relatedhttp://www.youtube.com/watch?v=MNbg4Go8NR0&feature=related


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http://www.youtube.com/watch?v=QgA6L2n476Y

http://www.youtube.com/watch?v=PmoybPcJPS8
http://www.youtube.com/watch?v=QgA6L2n476Yhttp://www.youtube.com/watch?v=PmoybPcJPS8http://www.youtube.com/watch?v=PmoybPcJPS8http://www.youtube.com/watch?v=PmoybPcJPS8http://www.youtube.com/watch?v=PmoybPcJPS8http://www.youtube.com/watch?v=QgA6L2n476Y


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http://www.colorado.edu/physics/2000/polarization/polarizationI.html

http://www.youtube.com/watch?v=Sdv0J57_U5g&feature=related
http://www.colorado.edu/physics/2000/polarization/polarizationI.htmlhttp://www.colorado.edu/physics/2000/polarization/polarizationI.htmlhttp://www.colorado.edu/physics/2000/polarization/polarizationI.htmlhttp://www.youtube.com/watch?v=Sdv0J57_U5g&feature=relatedhttp://www.youtube.com/watch?v=Sdv0J57_U5g&feature=relatedhttp://www.youtube.com/watch?v=Sdv0J57_U5g&feature=relatedhttp://www.youtube.com/watch?v=Sdv0J57_U5g&feature=relatedhttp://www.youtube.com/watch?v=Sdv0J57_U5g&feature=relatedhttp://www.youtube.com/watch?v=Sdv0J57_U5g&feature=relatedhttp://www.youtube.com/watch?v=Sdv0J57_U5g&feature=relatedhttp://www.colorado.edu/physics/2000/polarization/polarizationI.htmlhttp://www.colorado.edu/physics/2000/polarization/polarizationI.htmlhttp://www.colorado.edu/physics/2000/polarization/polarizationI.htmlhttp://www.colorado.edu/physics/2000/polarization/polarizationI.html


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George Enescu, Nicolae Gherbanovschi Manual clasa a XI-a, EdituraDidactica si Pedagogica 1994

Gabriela Cone Manual clasa a XI-a, Editura Books Unlimited Publishing

Octavian Rusu, C-tin Tristaru Manual clasa a XI-a, Editura Corint

Mircea Rusu, Mircea Nistor Manual clasa a XI-a, Editura Corint

Bibliografie

Traian Creu Fizic teorie i probleme volum II, Editura Tehnic, 1993

F. W.Sears, M. W. Zemansky, H. D. Young Fizica Editura Didactica siPedagogica 1983

G.G.Brtescu, Optica,Editura Didactica si Pedagogica 1982Ion Bunget, Lucian Burlacu, i alii, Compendiu de fizic, Edituratiinific, 1972

www,google/images


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http://www.flickr.com/photos/physicsclassroom/galleries/72157625101670351/

http://www.colorado.edu/physics/2000/polarization/polarizationI.html

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.html

http://www.enzim.hu/~szia/cddemo/edemo0.htm

http://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroism

http://physics.kenyon.edu/EarlyApparatus/Polarized_Light/Polarimeter/Polarimeter.html

http://www.f64.ro/articles/Filtrul_de_polarizare-I_.html

http://www.optics.arizona.edu/jcwyant/JoseDiaz/Polarization-Circular.htm
http://www.flickr.com/photos/physicsclassroom/galleries/72157625101670351/http://www.flickr.com/photos/physicsclassroom/galleries/72157625101670351/http://www.flickr.com/photos/physicsclassroom/galleries/72157625101670351/http://www.colorado.edu/physics/2000/polarization/polarizationI.htmlhttp://www.colorado.edu/physics/2000/polarization/polarizationI.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.htmlhttp://www.enzim.hu/~szia/cddemo/edemo0.htmhttp://www.enzim.hu/~szia/cddemo/edemo0.htmhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://physics.kenyon.edu/EarlyApparatus/Polarized_Light/Polarimeter/Polarimeter.htmlhttp://physics.kenyon.edu/EarlyApparatus/Polarized_Light/Polarimeter/Polarimeter.htmlhttp://physics.kenyon.edu/EarlyApparatus/Polarized_Light/Polarimeter/Polarimeter.htmlhttp://www.f64.ro/articles/Filtrul_de_polarizare-I_.htmlhttp://www.f64.ro/articles/Filtrul_de_polarizare-I_.htmlhttp://www.optics.arizona.edu/jcwyant/JoseDiaz/Polarization-Circular.htmhttp://www.optics.arizona.edu/jcwyant/JoseDiaz/Polarization-Circular.htmhttp://www.optics.arizona.edu/jcwyant/JoseDiaz/Polarization-Circular.htmhttp://www.optics.arizona.edu/jcwyant/JoseDiaz/Polarization-Circular.htmhttp://www.optics.arizona.edu/jcwyant/JoseDiaz/Polarization-Circular.htmhttp://www.optics.arizona.edu/jcwyant/JoseDiaz/Polarization-Circular.htmhttp://www.f64.ro/articles/Filtrul_de_polarizare-I_.htmlhttp://www.f64.ro/articles/Filtrul_de_polarizare-I_.htmlhttp://www.f64.ro/articles/Filtrul_de_polarizare-I_.htmlhttp://www.f64.ro/articles/Filtrul_de_polarizare-I_.htmlhttp://physics.kenyon.edu/EarlyApparatus/Polarized_Light/Polarimeter/Polarimeter.htmlhttp://physics.kenyon.edu/EarlyApparatus/Polarized_Light/Polarimeter/Polarimeter.htmlhttp://physics.kenyon.edu/EarlyApparatus/Polarized_Light/Polarimeter/Polarimeter.htmlhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.photophysics.com/tutorials/circular-dichroism-cd-spectroscopy/1-understanding-circular-dichroismhttp://www.enzim.hu/~szia/cddemo/edemo0.htmhttp://www.enzim.hu/~szia/cddemo/edemo0.htmhttp://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.htmlhttp://www.colorado.edu/physics/2000/polarization/polarizationI.htmlhttp://www.colorado.edu/physics/2000/polarization/polarizationI.htmlhttp://www.flickr.com/photos/physicsclassroom/galleries/72157625101670351/http://www.flickr.com/photos/physicsclassroom/galleries/72157625101670351/http://www.flickr.com/photos/physicsclassroom/galleries/72157625101670351/

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