{"id":2592,"date":"2016-11-11T01:53:09","date_gmt":"2016-11-11T01:53:09","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2592"},"modified":"2024-09-02T16:32:42","modified_gmt":"2024-09-02T16:32:42","slug":"reflexao-total","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/raciocinio-logico\/reflexao-total\/","title":{"rendered":"Reflex\u00e3o Total"},"content":{"rendered":"

Racioc\u00ednio L\u00f3gico<\/b><\/span><\/span><\/span><\/span><\/p>\n

Reflex\u00e3o Total<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

 <\/p>\n

 <\/p>\n

Como esse conte\u00fado envolve muita teoria, em caso de d\u00favidas voc\u00ea pode encontr\u00e1-la em <\/b><\/span><\/span><\/span>fisicaevestibular.com.br \u2013 \u00d3PTICA – Reflex\u00e3o Total<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

01-(UFU-MG)\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span>recipiente aberto, <\/b><\/span><\/span>conforme a <\/b><\/span><\/span>figura 1 <\/b><\/span><\/span>cont\u00e9m um <\/b><\/span><\/span>l\u00edquido de \u00edndice de refra\u00e7\u00e3o n(t)<\/b><\/span><\/span>, que <\/b><\/span><\/span>varia <\/b><\/span><\/span>com o <\/b><\/span><\/span>tempo (t) de acordo com a express\u00e3o <\/b><\/span><\/span>n(t) = n(ar). (1 + e<\/b><\/span><\/span>-bt<\/b><\/span><\/sup><\/span>),<\/b><\/span><\/span> <\/b>em que <\/b><\/span><\/span>b<\/b><\/span><\/span> \u00e9 uma constante positiva <\/b><\/span><\/span>e <\/b><\/span><\/span>n(ar) \u00e9 o \u00edndice de refra\u00e7\u00e3o do ar.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Quando a <\/b><\/span><\/span>luz passa do l\u00edquido para o ar, <\/b><\/span><\/span>\u00e9 <\/b><\/span><\/span>poss\u00edvel ocorrer o fen\u00f4meno de reflex\u00e3o total <\/b><\/span><\/span>para um <\/b><\/span><\/span>\u00e2ngulo de incid\u00eancia maior do que certo \u00e2ngulo limite,<\/b><\/span><\/span> (que \u00e9 <\/b><\/span><\/span>medido<\/b><\/span><\/span> em rela\u00e7\u00e3o \u00e0 <\/b><\/span><\/span>normal<\/b><\/span><\/span>).\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Assinale a <\/b><\/span><\/span>alternativa que melhor descreve a varia\u00e7\u00e3o do seno do \u00e2ngulo limite (sen \u2018limite\u2019) em fun\u00e7\u00e3o do tempo.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0<\/span><\/p>\n

02-(UNESP-SP)\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span>prisma de vidro imerso em \u00e1gua, <\/b><\/span><\/span>com a <\/b><\/span><\/span>face AB perpendicular \u00e0 face BC, <\/b><\/span><\/span>e a <\/b><\/span><\/span>face AC <\/b><\/span><\/span>com uma <\/b><\/span><\/span>inclina\u00e7\u00e3o de 45\u00b0 em rela\u00e7\u00e3o a AB, <\/b><\/span><\/span>\u00e9 <\/b><\/span><\/span>utilizado para desviar um feixe de luz monocrom\u00e1tico. <\/b><\/span><\/span><\/span><\/span>\"\"<\/p>\n

O <\/b><\/span><\/span>feixe penetra perpendicularmente \u00e0 face AB<\/b><\/span><\/span>, incidindo <\/b><\/span><\/span>na face AC com \u00e2ngulo de incid\u00eancia de 45\u00b0. <\/b><\/span><\/span>O <\/b><\/span><\/span>\u00e2ngulo limite para a ocorr\u00eancia de reflex\u00e3o total na face AC \u00e9 60\u00b0<\/b><\/span><\/span><\/span><\/span><\/p>\n

Considerando que <\/b><\/span><\/span>o \u00edndice de refra\u00e7\u00e3o do vidro \u00e9 maior que o da \u00e1gua, <\/b><\/span><\/span>a <\/b><\/span><\/span>trajet\u00f3ria que melhor representa o raio emergente <\/b><\/span><\/span>\u00e9<\/b><\/span><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span>I.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span>IV.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span>II.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span>V.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span>III.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

 <\/p>\n

03-(UFU-MG)\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span>raio de luz incide <\/b><\/span><\/span>de uma <\/b><\/span><\/span>regi\u00e3o que cont\u00e9m ar (\u00edndice de refra\u00e7\u00e3o n = 1,0), <\/b><\/span><\/span>em uma <\/b><\/span><\/span>placa de vidro <\/b><\/span><\/span>de <\/b><\/span><\/span>\u00edndice de refra\u00e7\u00e3o n = 1,5, <\/b><\/span><\/span>com um <\/b><\/span><\/span>\u00e2ngulo de incid\u00eancia igual a 30\u00b0, atravessando-a<\/b><\/span><\/span> e perfazendo a <\/b><\/span><\/span>trajet\u00f3ria AB da <\/b><\/span><\/span>figura a seguir.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Ap\u00f3s atravessar <\/b><\/span><\/span>a <\/b><\/span><\/span>placa de vidro, o raio passa por uma regi\u00e3o que cont\u00e9m um l\u00edquido sem sofrer desvio, <\/b><\/span><\/span>seguindo a <\/b><\/span><\/span>trajet\u00f3ria BC da figura acima, <\/b><\/span><\/span>atingindo a <\/b><\/span><\/span>superf\u00edcie de separa\u00e7\u00e3o do l\u00edquido com o ar (ponto C da figura).<\/b><\/span><\/span><\/span><\/span><\/p>\n

Dados:<\/b><\/span><\/span><\/span><\/span><\/p>\n

Velocidade da luz no v\u00e1cuo: <\/b><\/span><\/span>c = 3,0 \u00d7 10<\/b><\/span><\/span>8<\/b><\/span><\/sup><\/span>\u00a0m\/s.<\/b><\/span><\/span><\/span><\/span><\/p>\n

sen19,5\u00b0 = 1\/3\u00a0\u00a0\u00a0\u00a0\u00a0 sen30\u00b0 =1\/2\u00a0\u00a0\u00a0\u00a0\u00a0 sen41,8\u00b0 <\/b><\/span><\/span><\/span>= 2\/3\u00a0\u00a0\u00a0\u00a0\u00a0 sen70,5\u00b0 <\/b><\/span><\/span><\/span>= 0,94<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

Determine:<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span>o <\/b><\/span><\/span>\u00edndice de refra\u00e7\u00e3o <\/b><\/span><\/span>do <\/b><\/span><\/span>l\u00edquido.<\/b><\/span><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span>a <\/b><\/span><\/span>velocidade da luz <\/b><\/span><\/span>no <\/b><\/span><\/span>interior<\/b><\/span><\/span> do <\/b><\/span><\/span>vidro (percurso AB).<\/b><\/span><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span>se o <\/b><\/span><\/span>raio de luz emergir\u00e1 do l\u00edquido para o ar no ponto C, justificando<\/b><\/span><\/span> sua <\/b><\/span><\/span>resposta.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

04-(UFV-MG)\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span>enfeite de Natal <\/b><\/span><\/span>\u00e9 constitu\u00eddo por <\/b><\/span><\/span>cinco pequenas l\u00e2mpadas iguais e monocrom\u00e1ticas, <\/b><\/span><\/span>ligadas em <\/b><\/span><\/span>s\u00e9rie atrav\u00e9s de um fio esticado de comprimento 5L. <\/b><\/span><\/span><\/span><\/span><\/p>\n

Uma <\/b><\/span><\/span>das <\/b><\/span><\/span>pontas do fio est\u00e1 presa no centro de um disco de madeira, <\/b><\/span><\/span>de <\/b><\/span><\/span>raio R, <\/b><\/span><\/span>que <\/b><\/span><\/span>flutua na \u00e1gua <\/b><\/span><\/span>de uma <\/b><\/span><\/span>piscina. <\/b><\/span><\/span><\/span><\/span>\"\"<\/p>\n

A <\/b><\/span><\/span>outra ponta do fio est\u00e1 presa no fundo da piscina, <\/b><\/span><\/span>juntamente com <\/b><\/span><\/span>uma das l\u00e2mpadas, conforme representado na figura.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Durante a noite, <\/b><\/span><\/span>quando as <\/b><\/span><\/span>l\u00e2mpadas s\u00e3o acesas,<\/b><\/span><\/span> um <\/b><\/span><\/span>observador fora da piscina v\u00ea o brilho <\/b><\/span><\/span>de <\/b><\/span><\/span>apenas tr\u00eas das cinco l\u00e2mpadas. <\/b><\/span><\/span><\/span><\/span><\/p>\n

Sabendo que o <\/b><\/span><\/span>\u00edndice de refra\u00e7\u00e3o da \u00e1gua e o do ar s\u00e3o, respectivamente, n(H) e n(ar),<\/b><\/span><\/span> pergunta-se:<\/b><\/span><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span>Qual \u00e9 o <\/b><\/span><\/span>fen\u00f4meno<\/b><\/span><\/span> que <\/b><\/span><\/span>impede a visualiza\u00e7\u00e3o das l\u00e2mpadas?<\/b><\/span><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span>Qual <\/b><\/span><\/span>par de l\u00e2mpadas n\u00e3o \u00e9 vis\u00edvel?<\/b><\/span><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span>Qual \u00e9 a <\/b><\/span><\/span>rela\u00e7\u00e3o entre R, L, n(H) e n(ar) para que duas das l\u00e2mpadas n\u00e3o sejam vis\u00edveis?<\/b><\/span><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

05-(MACKENZIE-SP)\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span>raio luminoso <\/b><\/span><\/span>incide sobre um <\/b><\/span><\/span>cubo de vidro, <\/b><\/span><\/span>colocado <\/b><\/span><\/span>no ar (n<\/b><\/span><\/span>ar <\/b><\/span><\/sub><\/span>= 1), <\/b><\/span><\/span>como <\/b><\/span><\/span>mostra <\/b><\/span><\/span>a figura abaixo.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span>\u00edndice de refra\u00e7\u00e3o do vidro, <\/b><\/span><\/span>para que <\/b><\/span><\/span>haja internamente reflex\u00e3o total na face A, <\/b><\/span><\/span>deve ser:<\/b><\/span><\/span><\/span><\/span><\/p>\n

Dado:<\/b><\/span><\/span> sen 45<\/b><\/span><\/span>o<\/b><\/span><\/sup><\/span>\u00a0<\/b><\/span><\/span>=\u00a0\u221a2 \/2<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

 <\/p>\n

06-(UERJ-RJ)\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span>raio de luz,<\/b><\/span><\/span> deslocando-se <\/b><\/span><\/span>no ar, incide<\/b><\/span><\/span> em um dos <\/b><\/span><\/span>extremos de uma fibra \u00f3ptica F de \u00edndice de refra\u00e7\u00e3o n =\u221a2, <\/b><\/span><\/span>a um <\/b><\/span><\/span>\u00e2ngulo de incid\u00eancia\u00a0\"\"<\/b><\/span><\/span>1<\/b><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span>e <\/b><\/span><\/span>penetra na fibra a um \u00e2ngulo\"\"<\/b><\/span><\/span>2 <\/b><\/span><\/sub><\/span>= 30<\/b><\/span><\/span>o<\/b><\/span><\/sup><\/span>, conforme <\/b><\/span><\/span>figura. (n<\/b><\/span><\/span>ar <\/b><\/span><\/sub><\/span>= 1)<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

a) <\/b><\/span><\/span>calcule o <\/b><\/span><\/span>\u00e2ngulo de incid\u00eancia\u00a0\"\"<\/b><\/span><\/span>1<\/b><\/span><\/sub><\/span>.\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

b) Prove<\/b><\/span><\/span> que o <\/b><\/span><\/span>raio de luz, por reflex\u00e3o total, permanece completamente no interior da fibra.\u00a0\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\u00a0\u00a0<\/span><\/p>\n

07- (UNICAMP-SP)\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Ao <\/b><\/span><\/span>vermos miragens, <\/b><\/span><\/span>somos <\/b><\/span><\/span>levados a pensar que h\u00e1 \u00e1gua no ch\u00e3o de estradas. <\/b><\/span><\/span>O que <\/b><\/span><\/span>vemos \u00e9, na verdade, a reflex\u00e3o da<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

luz do c\u00e9u por uma camada de ar quente pr\u00f3xima ao solo.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Isso pode ser <\/b><\/span><\/span>explicado por um modelo simplificado como o da figura abaixo, <\/b><\/span><\/span>onde <\/b><\/span><\/span>n representa <\/b><\/span><\/span>o <\/b><\/span><\/span>\u00edndice de refra\u00e7\u00e3o. <\/b><\/span><\/span><\/span><\/span><\/p>\n

Numa <\/b><\/span><\/span>camada pr\u00f3xima ao solo, o ar \u00e9 aquecido, diminuindo<\/b><\/span><\/span> assim seu <\/b><\/span><\/span>\u00edndice de refra\u00e7\u00e3o n.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Considere a <\/b><\/span><\/span>situa\u00e7\u00e3o na qual o \u00e2ngulo de incid\u00eancia \u00e9 de 84\u00b0. <\/b><\/span><\/span>Adote <\/b><\/span><\/span>n<\/b><\/span><\/span>1<\/b><\/span><\/sub><\/span>\u00a0= 1,010 <\/b><\/span><\/span>e use a <\/b><\/span><\/span>aproxima\u00e7\u00e3o sen 84\u00b0 = 0,995.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

a) <\/b><\/span><\/span>Qual deve ser o <\/b><\/span><\/span>m\u00e1ximo valor de n<\/b><\/span><\/span>2<\/b><\/span><\/sub><\/span>\u00a0para que a miragem seja vista?<\/b><\/span><\/span> D\u00ea a <\/b><\/span><\/span>resposta<\/b><\/span><\/span> com <\/b><\/span><\/span>tr\u00eas casas decimais.<\/b><\/span><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span>Em <\/b><\/span><\/span>qual<\/b><\/span><\/span> das <\/b><\/span><\/span>camadas (1 ou 2) a velocidade da luz \u00e9 maior?<\/b><\/span><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

08-(UFG-GO)<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

 <\/p>\n

 <\/p>\n

Um <\/b><\/span><\/span>raio<\/b><\/span><\/span> de <\/b><\/span><\/span>luz monocrom\u00e1tico <\/b><\/span><\/span>incide <\/b><\/span><\/span>perpendicularmente na face A de um prisma e sofre reflex\u00f5es internas totais <\/b><\/span><\/span>com <\/b><\/span><\/span>toda luz emergindo pela face C, <\/b><\/span><\/span>como <\/b><\/span><\/span>ilustra <\/b><\/span><\/span>a figura. <\/b><\/span><\/span><\/span><\/span><\/p>\n

Considerando o <\/b><\/span><\/span>ex\u00adposto e sabendo que o meio externo \u00e9<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>o ar\u00a0(n<\/b><\/span><\/span>ar <\/b><\/span><\/sub><\/span>= 1)<\/b><\/span><\/span>,\u00a0<\/b><\/i><\/span><\/span>calcule o <\/b><\/span><\/span>\u00edndice de refra\u00e7\u00e3o m\u00ednimo do prisma.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

09-(UFF-RJ)\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span>fen\u00f4meno da miragem, <\/b><\/span><\/span>comum em <\/b><\/span><\/span>desertos, ocorre em locais onde a temperatura do solo \u00e9 alta. Raios luminosos <\/b><\/span><\/span>chegam aos <\/b><\/span><\/span>olhos de um observador por dois caminhos distintos, <\/b><\/span><\/span>um dos quais <\/b><\/span><\/span>parece proveniente de uma imagem especular do objeto observado, <\/b><\/span><\/span>como se <\/b><\/span><\/span>esse estivesse ao lado de um espelho d\u2019\u00e1gua (semelhante ao da superf\u00edcie de um lago).<\/b><\/span><\/span><\/span><\/span><\/p>\n

Um <\/b><\/span><\/span>modelo simplificado para a explica\u00e7\u00e3o desse fen\u00f4meno \u00e9 mostrado na figura abaixo.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

O <\/b><\/span><\/span>raio que parece provir da imagem especular sofre refra\u00e7\u00f5es sucessivas em diferentes camadas de ar pr\u00f3ximas ao solo.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Esse modelo reflete um racioc\u00ednio <\/b><\/span><\/span>que <\/b><\/span><\/span>envolve a temperatura, densidade e \u00edndice de refra\u00e7\u00e3o <\/b><\/span><\/span>de <\/b><\/span><\/span>cada uma das camadas.<\/b><\/span><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span>texto a seguir, <\/b><\/span><\/span>preenchidas suas <\/b><\/span><\/span>lacunas, exp\u00f5e esse racioc\u00ednio.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\u201cA temperatura do ar <\/b><\/span><\/span>___________________ <\/b><\/span><\/span>com a altura da camada, provocando _________________ da densidade e _________________ do \u00edndice de refra\u00e7\u00e3o; por isso, as refra\u00e7\u00f5es sucessivas do raio descendente fazem o \u00e2ngulo de refra\u00e7\u00e3o ______________ at\u00e9 que o raio sofra reflex\u00e3o total, acontecendo o inverso em sua trajet\u00f3ria ascendente at\u00e9 o olho do observador\u201d.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Assinale a <\/b><\/span><\/span>alternativa que completa corretamente <\/b><\/span><\/span>as lacunas.<\/b><\/span><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span>aumenta \u2013 diminui\u00e7\u00e3o \u2013 aumento \u2013 diminuir\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span>aumenta \u2013 diminui\u00e7\u00e3o \u2013 diminui\u00e7\u00e3o \u2013 diminuir\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span>diminui \u2013 aumento \u2013 aumento \u2013 aumentar\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span>diminui \u2013 aumento \u2013 diminui\u00e7\u00e3o \u2013 aumentar\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span>n\u00e3o varia \u2013 diminui\u00e7\u00e3o \u2013 diminui\u00e7\u00e3o \u2013 aumentar\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

10-(FUVEST-SP)<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Uma <\/b><\/span><\/span>fibra \u00f3tica \u00e9 um guia de luz, <\/b><\/span><\/span>flex\u00edvel e transparente, cil\u00edndrico, feito de <\/b><\/span><\/span>s\u00edlica ou pol\u00edmero, <\/b><\/span><\/span>de <\/b><\/span><\/span>di\u00e2metro n\u00e3o muito maior que o de um fio de cabelo<\/b><\/span><\/span>, usado para <\/b><\/span><\/span>transmitir sinais luminosos a grandes dist\u00e2ncias, com baixas perdas de<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

intensidade.<\/b><\/span><\/span> <\/b><\/span><\/span><\/p>\n

A <\/b><\/span><\/span>fibra \u00f3tica \u00e9 constitu\u00edda de um n\u00facleo, <\/b><\/span><\/span>por onde a <\/b><\/span><\/span>luz se propaga e de um revestimento, <\/b><\/span><\/span>como esquematizado <\/b><\/span><\/span>na figura acima (corte longitudinal). <\/b><\/span><\/span><\/span><\/span>\"\"<\/p>\n

Sendo o <\/b><\/span><\/span>\u00edndice de refra\u00e7\u00e3o do n\u00facleo 1,60 e o do revestimento, 1,45, <\/b><\/span><\/span>o <\/b><\/span><\/span>menor valor <\/b><\/span><\/span>do <\/b><\/span><\/span>\u00e2ngulo de incid\u00eancia \u03b8 do feixe luminoso, para que toda a luz incidente permane\u00e7a no n\u00facleo, \u00e9, aproximadamente,<\/b><\/span><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span>45<\/b><\/span><\/span>o\u00a0<\/b><\/span><\/sup><\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

b) <\/b><\/span><\/span>50<\/b><\/span><\/span>o\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/sup><\/span><\/span><\/span><\/p>\n

c) <\/b><\/span><\/span>55<\/b><\/span><\/span>o<\/b><\/span><\/sup><\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/span><\/p>\n

d) <\/b><\/span><\/span>60<\/b><\/span><\/span>o<\/b><\/span><\/sup><\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/span><\/p>\n

e) <\/b><\/span><\/span>65<\/b><\/span><\/span>o<\/b><\/span><\/sup><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

\u00a0<\/span><\/p>\n

11-(UFPE-PE)<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A figura <\/b><\/span><\/span>mostra um par de fibras \u00f3pticas, A e B, <\/b><\/span><\/span>dispostas <\/b><\/span><\/span>paralelamente e de mesmo comprimento. <\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span>pulso de luz \u00e9\u00a0 disparado em uma das extremidades das fibras. <\/b><\/span><\/span><\/span><\/span><\/p>\n

A luz se <\/b><\/span><\/span>propaga, parte pela fibra A, levando o tempo \u2206t<\/b><\/span><\/span>A<\/b><\/span><\/sub><\/span>\u00a0para percorrer a fibra , <\/b><\/span><\/span>e <\/b><\/span><\/span>parte pela fibra B , levando o tempo \u2206t<\/b><\/span><\/span>B<\/b><\/span><\/sub><\/span>\u00a0para percorrer a fibra. <\/b><\/span><\/span><\/span><\/span><\/p>\n

Os <\/b><\/span><\/span>\u00edndices de refra\u00e7\u00e3o dos materiais da fibra A e B s\u00e3o, respectivamente, n<\/b><\/span><\/span>A <\/b><\/span><\/sub><\/span>= 1,8 e n<\/b><\/span><\/span>B <\/b><\/span><\/sub><\/span>= 1,5. <\/b><\/span><\/span><\/span><\/span><\/p>\n

Calcule<\/b><\/span><\/span> o <\/b><\/span><\/span>atraso percentual da luz que vem pela fibra A, em rela\u00e7\u00e3o \u00e0 que vem pela fibra B. <\/b><\/span><\/span>ou seja, <\/b><\/span><\/span>determine a quantidade (\u2206t<\/b><\/span><\/span>A<\/b><\/span><\/sub><\/span>\/\u2206t<\/b><\/span><\/span>B<\/b><\/span><\/sub><\/span>\u00a0\u2013 1)x100%.\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

12-(UFMG-MG)<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Ariete <\/b><\/span><\/span>deseja estudar o <\/b><\/span><\/span>fen\u00f4meno da dispers\u00e3o da luz branca, <\/b><\/span><\/span>ou seja, a sua <\/b><\/span><\/span>decomposi\u00e7\u00e3o em v\u00e1rias cores devido \u00e0 depend\u00eancia do \u00edndice de refra\u00e7\u00e3o do material com a frequ\u00eancia. <\/b><\/span><\/span><\/span><\/span><\/p>\n

Para isso, ela <\/b><\/span><\/span>utiliza um prisma de vidro cuja se\u00e7\u00e3o reta tem a forma de um tri\u00e2ngulo ret\u00e2ngulo is\u00f3sceles.\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span>\u00edndice de refra\u00e7\u00e3o desse vidro \u00e9 n = 1,50 para a luz branca <\/b><\/span><\/span>e <\/b><\/span><\/span>varia<\/b><\/span><\/span> em torno <\/b><\/span><\/span>desse valor <\/b><\/span><\/span>para as <\/b><\/span><\/span>v\u00e1rias <\/b><\/span><\/span>cores do <\/b><\/span><\/span>espectro vis\u00edvel.<\/b><\/span><\/span><\/span><\/span><\/p>\n

(<\/b><\/span><\/span>Dados<\/b><\/span><\/span>: sen 45<\/b><\/span><\/span>o<\/b><\/span><\/sup><\/span>\u00a0= cos 45<\/b><\/span><\/span>o<\/b><\/span><\/sup><\/span>\u00a0<\/b><\/span><\/span>= 0,707<\/b><\/span><\/span>)<\/b><\/span><\/span><\/span><\/span><\/p>\n

Ela <\/b><\/span><\/span>envia um feixe de luz branca em uma dire\u00e7\u00e3o perpendicular<\/b><\/span><\/span> a uma das <\/b><\/span><\/span>superf\u00edcies do prisma que formam o \u00e2ngulo reto, <\/b><\/span><\/span>como mostrado <\/b><\/span><\/span>na figura.<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

1. <\/b><\/span><\/span>COMPLETE, na <\/b><\/span><\/span>figura, a trajet\u00f3ria do feixe at\u00e9 sair do prisma.<\/b><\/span><\/span><\/span><\/span><\/p>\n

2. <\/b><\/span><\/span>EXPLIQUE, <\/b><\/span><\/span>detalhando seu racioc\u00ednio, <\/b><\/span><\/span>o que <\/b><\/span><\/span>acontece com esse feixe na superf\u00edcie oposta ao \u00e2ngulo reto.<\/b><\/span><\/span><\/span><\/span><\/p>\n

3. <\/b><\/span><\/span>ASSINALE <\/b><\/span><\/span>com um X a op\u00e7\u00e3o correta.\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

Ariete observa <\/b><\/span><\/span>a <\/b><\/span><\/span>dispers\u00e3o da luz branca nesse experimento?<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

JUSTIFIQUE sua resposta.<\/b><\/span><\/span><\/span><\/span><\/p>\n

 <\/p>\n

13-(ENEM-MEC)<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

 <\/p>\n

Confira as resolu\u00e7\u00f5es comentadas<\/span><\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

Racioc\u00ednio L\u00f3gico Reflex\u00e3o Total     Como esse conte\u00fado envolve muita teoria, em caso de d\u00favidas voc\u00ea pode encontr\u00e1-la em fisicaevestibular.com.br \u2013 \u00d3PTICA – Reflex\u00e3o Total \u00a0 01-(UFU-MG)\u00a0 Um recipiente aberto, conforme a figura 1 cont\u00e9m um l\u00edquido de \u00edndice de refra\u00e7\u00e3o n(t), que varia com o tempo (t) de acordo com a express\u00e3o n(t) = n(ar). (1 + e-bt),<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2508,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-2592","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2592","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/comments?post=2592"}],"version-history":[{"count":2,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2592\/revisions"}],"predecessor-version":[{"id":2596,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2592\/revisions\/2596"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2508"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2592"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}