{"id":2248,"date":"2016-05-24T00:01:40","date_gmt":"2016-05-24T00:01:40","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2248"},"modified":"2024-09-02T14:28:21","modified_gmt":"2024-09-02T14:28:21","slug":"prismas","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/optica\/optica-geometrica\/prismas\/","title":{"rendered":"Prismas"},"content":{"rendered":"

Prismas<\/b><\/span><\/span><\/span><\/p>\n

Prisma \u00f3ptico<\/b><\/span><\/span><\/span><\/p>\n

Um <\/b><\/span><\/span><\/span>prisma \u00f3ptico <\/b><\/span><\/span><\/span>corresponde a um <\/b><\/span><\/span><\/span>conjunto<\/b><\/span><\/span><\/span> formado <\/b><\/span><\/span><\/span>por tr\u00eas meios homog\u00eaneos e transparentes <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

ou por <\/b><\/span><\/span><\/span>dois dioptros planos, <\/b><\/span><\/span><\/span>em que as <\/b><\/span><\/span><\/span>superf\u00edcies planas n\u00e3o s\u00e3o paralelas (faces do prisma) que se interceptam em retas que s\u00e3o as arestas.<\/b><\/span><\/span><\/span><\/p>\n

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

Tipos de prismas<\/b><\/span><\/span><\/span><\/p>\n

\"\" Prismas dispersivos \"\" <\/b><\/span><\/span><\/span> <\/b>decomp\u00f5em<\/b><\/span><\/span><\/span> (dispersam) a <\/b><\/span><\/span><\/span>luz policrom\u00e1tica branca <\/b><\/span><\/span><\/span>em suas <\/b><\/span><\/span><\/span>infinitas<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

componentes monocrom\u00e1ticas (cores) que comp\u00f5em o espectro luminoso.<\/b><\/span><\/span><\/span><\/p>\n

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

\"\" Prismas refletivos\u00a0<\/b><\/span><\/span><\/span>(de reflex\u00e3o total) \"\" <\/b><\/span><\/span><\/span>substituem os espelhos, com melhor rendimento, na<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

reflex\u00e3o da luz.<\/b><\/span><\/span><\/span><\/p>\n

C\u00e1lculo do desvio total ou desvio total angular (d)<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

As <\/b><\/span><\/span><\/span>superf\u00edcies S<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>, S<\/b><\/span><\/span><\/span>2 <\/b><\/span><\/span><\/sub><\/span>e S<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u00a0s\u00e3o as faces do prisma. <\/b><\/span><\/span><\/span>A <\/b><\/span><\/span><\/span>interse\u00e7\u00e3o das faces S<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0e S<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0determinam o <\/b><\/span><\/span><\/span>\u00e2ngulo\u00a0A<\/b><\/span><\/span><\/span> que \u00e9 <\/b><\/span><\/span><\/span>chamado de \u00e2ngulo de refring\u00eancia.<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>superf\u00edcie S<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>\u00a0que geralmente \u00e9 opaca \u00e9 utilizada apenas como apoio.<\/b><\/span><\/span><\/span><\/p>\n

Considere o <\/b><\/span><\/span><\/span>prisma da figura feito de material de \u00edndice de refra\u00e7\u00e3o n<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0e imerso num meio de \u00edndice de refra\u00e7\u00e3o n<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

Um <\/b><\/span><\/span><\/span>raio de luz monocrom\u00e1tico incide na face da esquerda com \u00e2ngulo de incid\u00eancia i e se refrata no interior do prisma com \u00e2ngulo de refra\u00e7\u00e3o r.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Aplicando a lei de <\/b><\/span><\/span><\/span>Snell-Descartes na face\u00a0da esquerda \"\" \u00a0n<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>.sen i = n<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>.sen r.<\/b><\/span><\/span><\/span><\/p>\n

Esse raio <\/b><\/span><\/span><\/span>incide na outra face com \u00e2ngulo de incid\u00eancia i\u2019 <\/b><\/span><\/span><\/span>e se <\/b><\/span><\/span><\/span>refrata novamente para o meio 1 com \u00e2ngulo de refra\u00e7\u00e3o r\u2019, tal que \u00a0\"\"\u00a0\u00a0n<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>.sen i\u2019 = n<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>.sen r\u2019.<\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>desvio total\u00a0ou desvio angular (d) <\/b><\/span><\/span><\/span>\u00e9 <\/b><\/span><\/span><\/span>definido como sendo o \u00e2ngulo entre os prolongamentos dos raios incidente na 1<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sup><\/span>\u00a0face e emergente na 2<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sup><\/span>\u00a0face.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Observe na figura ao lado que o desvio angular na 1<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sup><\/span>\u00a0face<\/b><\/span><\/span><\/span> (\u00e2ngulo entre o prolongamento do raio<\/b><\/span><\/span><\/span><\/p>\n

incidente e o do raio refratado) \"\"<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>somado ao <\/b><\/span><\/span><\/span>desvio angular na 2<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sup><\/span>\u00a0face <\/b><\/span><\/span><\/span>( \u00e2ngulo entre o prolongamento do raio emergente e o raio incidente) \"\"<\/b><\/span><\/span><\/span> nos fornece o desvio total d<\/b><\/span><\/span><\/span>, ou seja,\u00a0<\/b><\/span><\/span><\/span>d = (i – r) + (r\u2019- i\u2019)\u00a0\u00a0(I)<\/b><\/span><\/span><\/span><\/p>\n

Observe ainda na <\/b><\/span><\/span><\/span>mesma figura que o \u00e2ngulo de refring\u00eancia (A) do prisma \u00e9 fornecido pela express\u00e3o A = r + i<\/b><\/span><\/span><\/span>\u2019 \u00a0\"\" \u00a0<\/b><\/span><\/span><\/span>r = A – i\u2019\u00a0(II)<\/b><\/span><\/span><\/span><\/p>\n

Substituindo <\/b><\/span><\/span><\/span>II em I <\/b><\/span><\/span><\/span>obtemos a <\/b><\/span><\/span><\/span>f\u00f3rmula do desvio total:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

Desvio m\u00ednimo<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Prismas de reflex\u00e3o total<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span>Prismas de reflex\u00e3o total\u00a0 \"\"<\/b><\/span><\/span><\/span> Quando <\/b><\/span><\/span><\/span>a luz incide perpendicularmente \u00e0 uma das faces de um prisma, ele pode sofrer refra\u00e7\u00e3o sem sofrer desvio nesta face, reflex\u00e3o total na segunda face e emergir na<\/b><\/span><\/span><\/span>\"\"<\/p>\n

terceira face, tamb\u00e9m sem sofrer desvio. <\/b><\/span><\/span><\/span><\/p>\n

Os <\/b><\/span><\/span><\/span>prismas de reflex\u00e3o total mais usados <\/b><\/span><\/span><\/span>s\u00e3o constitu\u00eddos de um <\/b><\/span><\/span><\/span>tri\u00e2ngulo ret\u00e2ngulo is\u00f3sceles<\/b><\/span><\/span><\/span>, que <\/b><\/span><\/span><\/span>recebem a luz em posi\u00e7\u00f5es diferentes.<\/b><\/span><\/span><\/span><\/p>\n

Normalmente s\u00e3o de <\/b><\/span><\/span><\/span>vidro e imersos no ar, <\/b><\/span><\/span><\/span>substituindo os <\/b><\/span><\/span><\/span>espelhos planos com melhor rendimento.<\/b><\/span><\/span><\/span><\/p>\n

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

O que voc\u00ea deve saber, informa\u00e7\u00f5es e dicas<\/b><\/span><\/span><\/span><\/p>\n

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

\"\"<\/p>\n

\"\"<\/p>\n

\u00a0Embora a <\/b><\/span><\/span><\/span>refra\u00e7\u00e3o seja predominante, <\/b><\/span><\/span><\/span>ocorre tamb\u00e9m <\/b><\/span><\/span><\/span>absor\u00e7\u00e3o e reflex\u00e3o em ambas as faces do prisma.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

As <\/b><\/span><\/span><\/span>trajet\u00f3rias dos raios incidente, do refratado no interior do prisma e do emergente <\/b><\/span><\/span><\/span>se deslocam como se voc\u00ea estivesse <\/b><\/span><\/span><\/span>girando um \u201csaca-rolhas\u201d no sentido hor\u00e1rio<\/b><\/span><\/span><\/span>, ou seja, o <\/b><\/span><\/span><\/span>raio incidente sobe,<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

e os outros dois descem conforme a sequ\u00eancia das figuras acima.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Incid\u00eancia normal na primeira face do prisma<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

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

Ainda <\/b><\/span><\/span><\/span>neste caso, se o raio emergir rasante,<\/b><\/span><\/span><\/span> teremos que o <\/b><\/span><\/span><\/span>\u00e2ngulo de incid\u00eancia i\u2019 \u00e9 igual ao \u00e2ngulo <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

limite L, fornecido pela express\u00e3o<\/b><\/span><\/span><\/span> \"\" <\/b><\/span><\/span><\/span>senL = n<\/b><\/span><\/span><\/span>menor <\/b><\/span><\/span><\/sub><\/span>\/n<\/b><\/span><\/span><\/span>maior\u00a0<\/b><\/span><\/span><\/sub><\/span>\u00a0\"\"<\/b><\/span><\/span><\/span>\u00a0 senL =n<\/b><\/span><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/span>\/n\u00a0\"\" \u00a0<\/b><\/span><\/span><\/span>senL = 1\/n.<\/b><\/span><\/span><\/span><\/p>\n

Como i\u2019 = L \"\"<\/b><\/span><\/span><\/span><\/span>\u00a0 sen i\u2019 = sen L\u00a0\"\"\u00a0\u00a0<\/b><\/span><\/span><\/span><\/span>sen i\u2019 = 1\/n\u00a0<\/b><\/span><\/span><\/span><\/span>.\u00a0<\/b><\/span><\/span><\/span><\/span><\/p>\n

Portanto se <\/b><\/span><\/span><\/span>sen i\u2019 for igual a 1\/n, <\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/span>raio de luz emerge rasante e se, i\u2019 for maior que L, <\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/span>raio de luz sofre reflex\u00e3o total pois neste caso\u00a0sen L\u00a0>\u00a01\/n\u00a0.<\/b><\/span><\/span><\/span><\/p>\n

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

\"\"<\/p>\n

\u00a0Se <\/b><\/span><\/span><\/span>qualquer um dos dois prismas de reflex\u00e3o total<\/b><\/span><\/span><\/span> abaixo <\/b><\/span><\/span><\/span>tiver \u00edndice de refra\u00e7\u00e3o absoluto (n) e <\/b><\/span><\/span><\/span>\"\"<\/p>\n

estiver imerso no ar (n<\/b><\/span><\/span><\/span>ar <\/b><\/span><\/span><\/sub><\/span>= 1), o<\/b><\/span><\/span><\/span> <\/b>valor do \u00edndice de refra\u00e7\u00e3o\u00a0n\u00a0do prisma<\/b><\/span><\/span><\/span> <\/b>para que ocorra reflex\u00e3o total na <\/b><\/span><\/span><\/span>face interna <\/b><\/span><\/span><\/span>(figura 1) ou <\/b><\/span><\/span><\/span>faces internas <\/b><\/span><\/span><\/span>(figura 2) <\/b><\/span><\/span><\/span>deve <\/b><\/span><\/span><\/span>incidir com \u00e2ngulo superior ao \u00e2ngulo limite, ou seja i > L, ou ainda seni > senL\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 sen 45<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>\u00a0> senL\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>\u221a2\/2 > 1\/n\u00a0\u00a0\"\"<\/b><\/span><\/span><\/span>\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

n > \u221a2\u00a0> 1,4.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Experi\u00eancia de Newton na dispers\u00e3o da luz policrom\u00e1tica branca<\/b><\/span><\/span><\/span><\/p>\n

Veja como <\/b><\/span><\/span><\/span>Isaac Newton descreveu a proposta do experimento <\/b><\/span><\/span><\/span>que lhe <\/b><\/span><\/span><\/span>permitiu descartar <\/b><\/span><\/span><\/span>a <\/b><\/span><\/span><\/span>influ\u00eancia do vidro do prisma como causa da dispers\u00e3o da luz branca. <\/b><\/span><\/span><\/span>\"\"<\/p>\n

Considerando que a <\/b><\/span><\/span><\/span>fonte de luz era o orif\u00edcio O da janela do quarto de Newton<\/b><\/span><\/span><\/span>, veja a <\/b><\/span><\/span><\/span>descri\u00e7\u00e3o e o desenho da montagem executada por ele experi\u00eancia:<\/b><\/span><\/span><\/span><\/p>\n

“Eu peguei outro prisma igual ao primeiro e o coloquei de maneira que a luz fosse refratada de modos opostos ao passar atrav\u00e9s de ambos e, assim, ao final, voltaria a ser como era antes do primeiro prisma t\u00ea-la dispersado.”<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Exerc\u00edcios interessantes:<\/b><\/span><\/span><\/span><\/p>\n

01-<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Na <\/b><\/span><\/span><\/span>figura ao lado, est\u00e3o representados um prisma retangular<\/b><\/span><\/span><\/span>, cujos <\/b><\/span><\/span><\/span>\u00e2ngulos da base s\u00e3o iguais a 45<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>, <\/b><\/span><\/span><\/span>um objeto AB e o olho de um observador<\/b><\/span><\/span><\/span>. <\/b><\/span><\/span><\/span><\/p>\n

Devido ao <\/b><\/span><\/span><\/span>fen\u00f4meno da reflex\u00e3o total, <\/b><\/span><\/span><\/span>os <\/b><\/span><\/span><\/span>raios de luz provenientes do objeto s\u00e3o refletidos na base do prisma, que funciona como um espelho plano.<\/b><\/span><\/span><\/span><\/p>\n

Esquematize a imagem A\u2019B\u2019 do objeto AB <\/b><\/span><\/span><\/span>visto pelo observador:<\/b><\/span><\/span><\/span><\/p>\n

 <\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

Na figura o <\/b><\/span><\/span><\/span>raio de luz vertical e para cima que sai de A <\/b><\/span><\/span><\/span>penetra no prisma <\/b><\/span><\/span><\/span>sem sofrer desvio, <\/b><\/span><\/span><\/span>sofre<\/b><\/span><\/span><\/span><\/p>\n

reflex\u00e3o total na face interna inclinada e sai horizontalmente do prisma sem sofrer desvio e atinge os olhos do observador que v\u00ea a imagem A\u2019 de A.<\/b><\/span><\/span><\/span><\/p>\n

O mesmo processo \u00e9 realizado <\/b><\/span><\/span><\/span>pelo raio de luz que sai de B <\/b><\/span><\/span><\/span>e atinge os <\/b><\/span><\/span><\/span>olhos do observador que v\u00ea B\u2019. <\/b><\/span><\/span><\/span><\/p>\n

Unindo A\u2019 com B\u2019 voc\u00ea localiza a imagem A\u2019B\u2019 de AB vista pelo observador.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

02-<\/b><\/span><\/span><\/span> <\/b>Um <\/b><\/span><\/span><\/span>tipo<\/b><\/span><\/span><\/span> de sinaliza\u00e7\u00e3o utilizado em estradas e avenidas <\/b><\/span><\/span><\/span>\u00e9 o chamado <\/b><\/span><\/span><\/span>olho-de-gato, <\/b><\/span><\/span><\/span>o qual consiste na <\/b><\/span><\/span><\/span>justaposi\u00e7\u00e3o de v\u00e1rios prismas retos feitos de pl\u00e1sticos que refletem a luz incidente dos far\u00f3is dos autom\u00f3veis.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

a) <\/b><\/span><\/span><\/span>Reproduza o <\/b><\/span><\/span><\/span>prisma ABC representado na figura abaixo <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>desenhe a trajet\u00f3ria de um raio de luz que incide perpendicularmente sobre a face OG e sofre reflex\u00f5es totais nas superf\u00edcies AC e <\/b><\/span><\/span><\/span>BC.<\/b><\/span><\/span><\/span><\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

a) <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

b) <\/b><\/span><\/span><\/span>Determine o <\/b><\/span><\/span><\/span>m\u00ednimo valor do \u00edndice de refra\u00e7\u00e3o do pl\u00e1stico acima <\/b><\/span><\/span><\/span>do qual o <\/b><\/span><\/span><\/span>prisma<\/b><\/span><\/span><\/span> funciona como um <\/b><\/span><\/span><\/span>refletor perfeito de luz <\/b><\/span><\/span><\/span>(toda luz que <\/b><\/span><\/span><\/span>incide perpendicularmente \u00e0 superf\u00edcie OG<\/b><\/span><\/span><\/span> \u00e9 <\/b><\/span><\/span><\/span>refletida<\/b><\/span><\/span><\/span>). Considere o <\/b><\/span><\/span><\/span>prisma no ar, onde o \u00edndice de refra\u00e7\u00e3o vale 1,0.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Para que haja <\/b><\/span><\/span><\/span>reflex\u00e3o total\u00a0\u00a0\"\"<\/b><\/span><\/span><\/span>\u00a0\u00a0<\/b><\/span><\/span><\/span>i > L \"\"<\/b><\/span><\/span><\/span>\u00a0\u00a0<\/b><\/span><\/span><\/span>seni > senL\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 sen45<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>\u00a0> senL\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>\u221a2\/2 ><\/b><\/span><\/span><\/span> 1\/n\u00a0\u00a0\"\"<\/b><\/span><\/span><\/span>\u00a0\u00a0<\/b><\/span><\/span><\/span>n > \u221a2.<\/b><\/span><\/span><\/span><\/p>\n

03- <\/b><\/span><\/span><\/span>Um <\/b><\/span><\/span><\/span>raio monocrom\u00e1tico de luz incide no ponto A <\/b><\/span><\/span><\/span>de uma das <\/b><\/span><\/span><\/span>faces de um prisma <\/b><\/span><\/span><\/span>feito de <\/b><\/span><\/span><\/span>vidro e imerso no ar. <\/b><\/span><\/span><\/span><\/p>\n

A <\/b><\/span><\/span><\/span>figura 1<\/b><\/span><\/span><\/span> representa <\/b><\/span><\/span><\/span>apenas o raio incidente i e o raio refratado r <\/b><\/span><\/span><\/span>num <\/b><\/span><\/span><\/span>plano normal \u00e0s faces do prisma,<\/b><\/span><\/span><\/span> cujas <\/b><\/span><\/span><\/span>aresta<\/b><\/span><\/span><\/span>s s\u00e3o representadas pelos <\/b><\/span><\/span><\/span>pontos P, S e T, <\/b><\/span><\/span><\/span>formando um <\/b><\/span><\/span><\/span>tri\u00e2ngulo eq\u00fcil\u00e1tero.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Os <\/b><\/span><\/span><\/span>pontos A, B e C tamb\u00e9m formam um tri\u00e2ngulo equil\u00e1tero<\/b><\/span><\/span><\/span> e s\u00e3o, <\/b><\/span><\/span><\/span>respectivamente, equidistantes <\/b><\/span><\/span><\/span>de <\/b><\/span><\/span><\/span>P e S, S e T, e T e P.<\/b><\/span><\/span><\/span> Considere os <\/b><\/span><\/span><\/span>raios E<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>, E<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>, E<\/b><\/span><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/span>, E<\/b><\/span><\/span><\/span>4<\/b><\/span><\/span><\/sub><\/span>\u00a0e E<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sub><\/span>, <\/b><\/span><\/span><\/span>que se <\/b><\/span><\/span><\/span>afastam do prisma, <\/b><\/span><\/span><\/span>representados na <\/b><\/span><\/span><\/span>figura 2.<\/b><\/span><\/span><\/span><\/p>\n

Podemos <\/b><\/span><\/span><\/span>afirmar que os raios compat\u00edveis com as reflex\u00f5es e refra\u00e7\u00f5es sofridas pelo raio incidente, no prisma<\/b><\/span><\/span><\/span>, s\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Refra\u00e7\u00e3o no ponto A\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 <\/b><\/span><\/span><\/span>n<\/b><\/span><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/span>.sen60<\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/sup><\/span>= n<\/b><\/span><\/span><\/span>v<\/b><\/span><\/span><\/sub><\/span>.senr\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 1.\u221a3\/2 = n<\/b><\/span><\/span><\/span>v<\/b><\/span><\/span><\/sub><\/span>.sen30<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>\u00a0 \"\"\u00a0 1.\u221a3\/2 = n<\/b><\/span><\/span><\/span>v<\/b><\/span><\/span><\/sub><\/span>.1\/2\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>n<\/b><\/span><\/span><\/span>v <\/b><\/span><\/span><\/sub><\/span>= \u221a3\u00a0(\u00edndice de refra\u00e7\u00e3o do vidro).<\/b><\/span><\/span><\/span><\/p>\n

Quando <\/b><\/span><\/span><\/span>atinge o ponto B o raio de luz sofre refra\u00e7\u00e3o <\/b><\/span><\/span><\/span>passando para o ar onde <\/b><\/span><\/span><\/span>n<\/b><\/span><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/span> = 1<\/b><\/span><\/span><\/span>, pois <\/b><\/span><\/span><\/span>sen30<\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/sup><\/span>=<\/b><\/span><\/span><\/span> <\/b>1\/2 <\/b><\/span><\/span><\/span>e <\/b><\/span><\/span><\/span>senL = n<\/b><\/span><\/span><\/span>menor<\/b><\/span><\/span><\/sub><\/span>\/n<\/b><\/span><\/span><\/span>maior <\/b><\/span><\/span><\/sub><\/span>= 1\/\u221a3 = <\/b><\/span><\/span><\/span>\u221a3\/3\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 assim, como <\/b><\/span><\/span><\/span>seni < senL<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>i < L<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0 ele <\/b><\/span><\/span><\/span>n\u00e3o sofre reflex\u00e3o total em B<\/b><\/span><\/span><\/span>, sofrendo <\/b><\/span><\/span><\/span>refra\u00e7\u00e3o<\/b><\/span><\/span><\/span> e <\/b><\/span><\/span><\/span>passando para o ar.<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Aplicando <\/b><\/span><\/span><\/span>Snell-Descartes no ponto B\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 <\/b><\/span><\/span><\/span>n<\/b><\/span><\/span><\/span>v<\/b><\/span><\/span><\/sub><\/span>.sen30<\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/sup><\/span>= n<\/b><\/span><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/span>.senr\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 \u221a3.1\/2 = 1.senr\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>senr =<\/b><\/span><\/span><\/span><\/p>\n

\u221a3\/2\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 <\/b><\/span><\/span><\/span>r = 60<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0\u00a0<\/b><\/span><\/span><\/span>R- A<\/b><\/span><\/span><\/span><\/p>\n

04- <\/b><\/span><\/span><\/span>Um <\/b><\/span><\/span><\/span>prisma triangular desvia<\/b><\/span><\/span><\/span> um <\/b><\/span><\/span><\/span>feixe de luz verde de um \u00e2ngulo<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>\u04e8<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>, em rela\u00e7\u00e3o \u00e0 <\/b><\/span><\/span><\/span>dire\u00e7\u00e3o de incid\u00eancia,<\/b><\/span><\/span><\/span> como ilustra a <\/b><\/span><\/span><\/span>figura A.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Se uma <\/b><\/span><\/span><\/span>placa plana, do mesmo material do prisma, for colocada entre a<\/b><\/span><\/span><\/span> <\/b>fonte de luz e o prisma<\/b><\/span><\/span><\/span>, nas posi\u00e7\u00f5es mostradas <\/b><\/span><\/span><\/span>nas figuras B e C, a luz, ao sair do prisma, ser\u00e1 desviada, <\/b><\/span><\/span><\/span>respectivamente,<\/b><\/span><\/span><\/span><\/p>\n

\"\"de <\/b><\/span><\/span><\/span>\u00e2ngulos<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>\u04e8<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0<\/b><\/span><\/span><\/sub><\/span>e \u04e8<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span>, em <\/b><\/span><\/span><\/span>rela\u00e7\u00e3o \u00e0 dire\u00e7\u00e3o de incid\u00eancia indicada pela seta.<\/b><\/span><\/span><\/span><\/p>\n

Os <\/b><\/span><\/span><\/span>desvios angulares ser\u00e3o tais que<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Sempre que um <\/b><\/span><\/span><\/span>feixe de luz monocrom\u00e1tica <\/b><\/span><\/span><\/span>(uma s\u00f3 cor, no caso, verde) incide sobre uma <\/b><\/span><\/span><\/span>l\u00e2mina de faces paralelas (placa plana do exerc\u00edcio) imersa em um mesmo meio, o raio incidente e o raio emergente s\u00e3o paralelos<\/b><\/span><\/span><\/span> <\/b>n\u00e3o<\/b><\/span><\/span><\/span> sofrendo <\/b><\/span><\/span><\/span>mudan\u00e7a na dire\u00e7\u00e3o, no caso horizontal, veja a an\u00e1lise nas figuras abaixo:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

R- A<\/b><\/span><\/span><\/span><\/p>\n

 <\/p>\n

Confira os exerc\u00edcios com resolu\u00e7\u00e3o comentada<\/span><\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

Prismas Prisma \u00f3ptico Um prisma \u00f3ptico corresponde a um conjunto formado por tr\u00eas meios homog\u00eaneos e transparentes ou por dois dioptros planos, em que as superf\u00edcies planas n\u00e3o s\u00e3o paralelas (faces do prisma) que se interceptam em retas que s\u00e3o as arestas. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Tipos de prismas Prismas dispersivos decomp\u00f5em (dispersam) a luz policrom\u00e1tica branca em suas infinitas componentes monocrom\u00e1ticas (cores)<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2137,"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-2248","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2248","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=2248"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2248\/revisions"}],"predecessor-version":[{"id":2255,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2248\/revisions\/2255"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2137"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2248"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}