{"id":2589,"date":"2016-11-11T01:49:52","date_gmt":"2016-11-11T01:49:52","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2589"},"modified":"2024-09-02T16:35:01","modified_gmt":"2024-09-02T16:35:01","slug":"refracao-da-luz-resolucao","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/raciocinio-logico\/refracao-da-luz\/refracao-da-luz-resolucao\/","title":{"rendered":"Refra\u00e7\u00e3o da Luz – Resolu\u00e7\u00e3o"},"content":{"rendered":"

Resolu\u00e7\u00f5es comentadas dos exerc\u00edcios de vestibulares sobre <\/b><\/span><\/span><\/span><\/p>\n

Refra\u00e7\u00e3o da Luz<\/b><\/span><\/span><\/span><\/p>\n

01-<\/b><\/span><\/span><\/span> <\/b>Durante o dia predomina a refra\u00e7\u00e3o (luz externa mais intensa) e a noite a reflex\u00e3o(luz interna mais intensa<\/b><\/span><\/span><\/span><\/p>\n

02-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) No ar (fora e dentro da esfera), a velocidade do raio de luz \u00e9 de 3,0.10<\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/sup><\/span>cm\/s e no vidro de \u00edndice de refra\u00e7\u00e3o n<\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/sub><\/span>=1,5 vale n<\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/sub><\/span>=C\/V<\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 1,5=3.10<\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/sup><\/span>\/V<\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 V<\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/sub><\/span>=2,0.10<\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/sup><\/span>cm\/s\u00a0 —\u00a0 para atravessar cada uma das paredes de d=6,0cm de espessura, com velocidade de V=2,0.10<\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/sup><\/span>\u00a0m\/s a luz demora\u00a0 —\u00a0 V=d\/t\u00a0 —\u00a0 2.10<\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/sup><\/span>\u00a0=6\/t\u00a0 —\u00a0 t=3.10<\/b><\/span><\/span><\/span>-10<\/b><\/span><\/span><\/sup><\/span>\u00a0s e para atravessar a parte com ar no interior da esfera demora\u00a0 —\u00a0 3.10<\/b><\/span><\/span><\/span>10<\/b><\/span><\/span><\/sup><\/span>\u00a0= (20 \u2013 12)\/t\u00a0 —\u00a0 t=6.10<\/b><\/span><\/span><\/span>-10<\/b><\/span><\/span><\/sup><\/span>s<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

b) t=(18 \u2013 6).10<\/b><\/span><\/span><\/span>-10<\/b><\/span><\/span><\/sup><\/span>\u00a0\u00a0—\u00a0 t=1,2.10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>s<\/b><\/span><\/span><\/span><\/p>\n

03-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Observe na figura abaixo, que na dispers\u00e3o da luz solar que provoca o arco-\u00edris, a luz retorna ao meio original e, para que isso aconte\u00e7a o Sol tem que estar atr\u00e1s do observador\u00a0\u00a0—\u00a0R- D<\/b><\/span><\/span><\/span><\/p>\n

04-<\/b><\/span><\/span><\/span>I. Falsa—\u00a0\u00a0veja as figuras abaixo:\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

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

II. Correta—\u00a0\u00a0<\/b><\/span><\/span><\/span>A\u00a0<\/b><\/span><\/span><\/span><\/span>Dispers\u00e3o luminosa no\u00a0arco-\u00edris ocorre\u00a0naturalmente\u00a0e \u00e9 resultado do espalhamento da luz em gotas de \u00e1gua em suspens\u00e3o na atmosfera, ou artificialmente quando a luz se dispersa como no interior de um prisma (figura\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

da esquerda) ou passa do ar para a \u00e1gua (figura da direita).<\/b><\/span><\/span><\/span><\/p>\n

III. Falsa—\u00a0\u00a0Difra\u00e7\u00e3o \u00e9 o fen\u00f4meno que permite com que a luz se espalhe contornando obst\u00e1culos ou atravessando uma fenda\u00a0\u00a0—\u00a0\u00a0por exemplo, se\u00a0um pincel de luz monocrom\u00e1tica (uma s\u00f3 cor) incidir sobre uma tela opaca (obst\u00e1culo) A,\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

com uma estreita fenda S<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>, ele consegue atravess\u00e1-la, se espalhando e\u00a0\u00a0sofrendo difra\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

IV. Correta <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Na figura com a luz policrom\u00e1tica branca incidindo na gota de \u00e1gua, voc\u00ea observa o seguinte,\u00a0\u00a0em 1\u00a0ocorre refra\u00e7\u00e3o, em 2 reflex\u00e3o, e em 3 nova refra\u00e7\u00e3o\u00a0\u00a0—\u00a0\u00a0entre 1 e 2 e entre 2 e 3, ocorre dispers\u00e3o\u00a0\u00a0—\u00a0\u00a0R- B.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

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

05-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>S\u00e3o infinitas as frequ\u00eancias (cores) que comp\u00f5em a luz policrom\u00e1tica branca proveniente do <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Sol e uma quantidade muito grande de frequ\u00eancias do espectro eletromagn\u00e9tico vis\u00edvel (veja tabela \u00a0\u00a0—\u00a0\u00a0R- D.<\/b><\/span><\/span><\/span><\/p>\n

06-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>De acordo com o enunciado, o metamaterial apresenta propriedades e comportamentos que n\u00e3o s\u00e3o encontrados em materiais naturais\u00a0 —\u00a0 portanto, a \u00fanica alternativa que pode representar a refra\u00e7\u00e3o da luz ao passar para o metamaterial \u00e9 a D, que n\u00e3o pode acontecer pois, os raios de luz incidentes e refratados devem estar em quadrantes opostos —\u00a0\u00a0R- D<\/b><\/span><\/span><\/span><\/p>\n

07-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Como a atmosfera \u00e9 mais densa nas camadas inferiores, nelas o \u00edndice de refra\u00e7\u00e3o \u00e9 maior que <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

nas camadas superiores e o raio de luz, a medida que desce vai se aproximando da normal\u00a0\u00a0—\u00a0\u00a0R- C.<\/b><\/span><\/span><\/span><\/p>\n

08-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Como a luz incide perpendicularmente a uma das faces do cubo, ela n\u00e3o sofre desvio (incid\u00eancia normal)<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Observe no gr\u00e1fico que o cubo tem\u00a0 aresta a=(50 \u2013 30).10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>=20.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>m =2.10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>m e que a luz demora t=(2 \u2013 1).10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>s=10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>s para atravess\u00e1-lo\u00a0\u00a0—\u00a0velocidade da luz no meio exterior ao cubo\u00a0 —\u00a0 V<\/b><\/span><\/span><\/span>e<\/b><\/span><\/span><\/sub><\/span>=d\/t=30.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>\/1.10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 V<\/b><\/span><\/span><\/span>e<\/b><\/span><\/span><\/sub><\/span>=3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>m\/s\u00a0 —\u00a0 velocidade da luz no interior do cubo\u00a0 —\u00a0 V<\/b><\/span><\/span><\/span>i<\/b><\/span><\/span><\/sub><\/span>=a\/t=2.10<\/b><\/span><\/span><\/span>-1<\/b><\/span><\/span><\/sup><\/span>\/10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 V<\/b><\/span><\/span><\/span>i<\/b><\/span><\/span><\/sub><\/span>=2.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>m\/s\u00a0 —\u00a0 o meio mais refringente \u00e9 o cubo, pois nele a luz tem menor velocidade\u00a0 —\u00a0 n<\/b><\/span><\/span><\/span>e<\/b><\/span><\/span><\/sub><\/span>\/n<\/b><\/span><\/span><\/span>i<\/b><\/span><\/span><\/sub><\/span>=V<\/b><\/span><\/span><\/span>i<\/b><\/span><\/span><\/sub><\/span>\/V<\/b><\/span><\/span><\/span>e<\/b><\/span><\/span><\/sub><\/span>=2.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\/3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0\u00a0n<\/b><\/span><\/span><\/span>e<\/b><\/span><\/span><\/sub><\/span>\/n<\/b><\/span><\/span><\/span>i<\/b><\/span><\/span><\/sub><\/span>=1,5<\/b><\/span><\/span><\/span><\/p>\n

b) Veja resolu\u00e7\u00e3o (a)\u00a00,2m\u00a0ou 20cm<\/b><\/span><\/span><\/span><\/p>\n

09-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Para que o observador veja o ponto B, com o tanque completamente cheio de l\u00edquido, sob o mesmo raio visual que o ponto A, o raio de luz tem que sair de B, atingir Q onde sofre refra\u00e7\u00e3o com \u00e2ngulo de incid\u00eancia i e de refra\u00e7\u00e3o r at\u00e9 atingir o olho do observador, seguindo o caminho BQO.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Aplicar Pit\u00e1goras no tri\u00e2ngulo APQ e achar AQ\u00a0 —\u00a0 (AQ)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0= (AP)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0+ (PQ)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 (AQ)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>= L<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0+ (L\/4)<\/b><\/span><\/span><\/span>2\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0\u00a0—\u00a0\u00a0(AQ) =\u221a17 . (L\/4)\u00a0\u00a0 Ainda no tri\u00e2ngulo APQ achar sen r\u00a0 —\u00a0 senr=(AP)(AQ)\u00a0 —\u00a0 senr=L\/\u221a17 . L\/4=4\/\u221a17\u00a0 —\u00a0\u00a0senr =4(\u221a17)\/17<\/b><\/span><\/span><\/span><\/p>\n

\u00a0Usar Snell-Descartes na refra\u00e7\u00e3o do l\u00edquido para o ar no ponto Q\u00a0\u00a0 —\u00a0\u00a0 —\u00a0\u00a0 n<\/b><\/span><\/span><\/span>l\u00edquido<\/b><\/span><\/span><\/sub><\/span>.seni=n<\/b><\/span><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/span>.senr\u00a0\u00a0 —\u00a0\u00a0 n.sen45<\/b><\/span><\/span><\/span>o\u00a0<\/b><\/span><\/span><\/sup><\/span>= 1.4(\u221a17)\/17\u00a0\u00a0—\u00a0\u00a0n.\u221a2\/2=4\u221a17\/17\u00a0\u00a0 —\u00a0\u00a0\u00a0n=4\u221a34\/17\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

10-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>O desvio (d) na refra\u00e7\u00e3o corresponde ao \u00e2ngulo entre o prolongamento do raio incidente e o raio refratado\u00a0 —\u00a0 observe na figura que o desvio d vale\u00a0 —\u00a0 d= i \u2013 r\u00a0\u00a0 —\u00a0 aplicando a lei de Snell\u00a0 —\u00a0 n<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>.seni =n<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>.senr\u00a0 —\u00a0 1.seni = n<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>.senr\u00a0<\/b><\/span><\/span><\/span>\"\"<\/p>\n

—\u00a0 senr=seni\/n<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 essa express\u00e3o indica que n<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0\u00e9 inversamente proporcional a senr e consequentemente a r\u00a0 —observe na figura que quanto maior for o \u00e2ngulo de refra\u00e7\u00e3o r, menor ser\u00e1 o desvio d\u00a0 — ent\u00e3o, para que o raio de luz sofra menor desvio, ele dever\u00e1 possuir maior \u00e2ngulo de refra\u00e7\u00e3o r o que ocorrer\u00e1 quando o \u00edndice de refra\u00e7\u00e3o n<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0for o menor poss\u00edvel\u00a0 —\u00a0\u00a0consultando a tabela, o menor \u00edndice de refra\u00e7\u00e3o \u00e9 o da \u00e1gua\u00a0 —\u00a0\u00a0R- A<\/b><\/span><\/span><\/span><\/p>\n

11-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Observe a figura abaixo\u00a0 —\u00a0 \u00e0 medida que os raios de luz provenientes do Sol penetram na <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

atmosfera da Terra, v\u00e3o encontrando camadas de ar cada vez mais densas, mais refringentes e de maiores \u00edndices de refra\u00e7\u00e3o e aproximam-se cada vez mais da normal sofrendo os desvios mostrados\u00a0 —\u00a0 esses desvios fazem com que a imagem que se observa do Sol ao amanhecer e ao anoitecer\u00a0 encontra-se acima de sua real posi\u00e7\u00e3o, tomando-se como refer\u00eancia o horizonte. —\u00a0 R- C<\/b><\/span><\/span><\/span><\/p>\n

12-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>A resposta s\u00f3 pode estar entre as alternativas A, D ou C, pois D<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0capta a luz emitida na vertical onde n\u00e3o sofre desvio (incid\u00eancia normal), assim o indicador s\u00f3 pode estar na vertical. Quando se refrata do vidro (\u00e1gua) para o ar a luz sofre desvio, se\u00a0afastando\u00a0da normal, at\u00e9 atingir D<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>. A \u00fanica alternativa que satisfaz \u00e9 a\u00a0C.<\/b><\/span><\/span><\/span><\/p>\n

13-<\/b><\/span><\/span><\/span> <\/b>Aplicando a lei de Snell-Descartes na superf\u00edcie de separa\u00e7\u00e3o dos meios A e B\u00a0\u00a0—\u00a0\u00a0n<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>sen7<\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/sup><\/span>= <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0\u00a0n<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>senr\u00a0\u00a0—\u00a0\u00a01.0,12=1,2.senr — senr=0,1\u00a0\u00a0—\u00a0\u00a0\u00a0tra\u00e7ando o caminho percorrido pelo raio de luz\u00a0\u00a0—\u00a0\u00a0todo raio de luz que incide no espelho passando\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

pelo foco principal F, sofre reflex\u00e3o e emerge paralelamente ao eixo principal (ep)\u00a0\u00a0—\u00a0\u00a0observe a figura abaixo onde est\u00e3o colocados os valores fornecidos e a dist\u00e2ncia d pedida\u00a0\u00a0—\u00a0\u00a0lembrando que, para \u00e2ngulos pequenos (menores que\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

10<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>), no caso, i=7<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>\u00a0e r<i, os valores do seno e da tangente s\u00e3o aproximadamente iguais ent\u00e3o voc\u00ea pode fazer senr=tgr =0.1\u00a0\u00a0—\u00a0\u00a0no tri\u00e2ngulo hachurado\u00a0\u00a0—\u00a0\u00a0tgr=cateto oposto\/cateto adjacente=d\/3\u00a0\u00a0—0,1=d\/3\u00a0\u00a0—\u00a0\u00a0d=0,3m=30cm\u00a0\u00a0—\u00a0\u00a0R- E.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

14-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Aplicando a lei de Snell-Descartes na interface prisma-l\u00edquido\u00a0\u00a0—\u00a0\u00a0n<\/b><\/span><\/span><\/span>p<\/b><\/span><\/span><\/sub><\/span>.seni=n<\/b><\/span><\/span><\/span>l<\/b><\/span><\/span><\/sub><\/span>senr\u00a0\u00a0\u00a0—\u00a0\u00a01,6.sen45<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>=n<\/b><\/span><\/span><\/span>l<\/b><\/span><\/span><\/sub><\/span>.senr\u00a0\u00a0—\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

senr=1,6.\u221a2\/2n<\/b><\/span><\/span><\/span>l<\/b><\/span><\/span><\/sub><\/span>\u00a0(I)\u00a0\u00a0—\u00a0\u00a0no tri\u00e2ngulo hachurado\u00a0\u00a0—\u00a0\u00a0Pit\u00e1goras\u00a0\u00a0—\u00a0\u00a0d<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>=4<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0+ (\u221a2)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>=16 + 2\u00a0\u00a0—\u00a0\u00a0d=\u221a18cm\u00a0\u00a0—\u00a0\u00a0ainda no tri\u00e2ngulo hachurado\u00a0\u00a0—\u00a0\u00a0senr=4\/\u221a18 (II)\u00a0\u00a0—\u00a0\u00a0(II) em (I)\u00a0\u00a0—\u00a0\u00a01,6.\u221a2\/2n<\/b><\/span><\/span><\/span>l<\/b><\/span><\/span><\/sub><\/span>=4\/\u221a18\u00a0\u00a0—\u00a0\u00a08n<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= 1,6.\u221a2.\u221a18\u00a0\u00a0—\u00a0\u00a0n<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=1,6.\u221a36\/8=<\/b><\/span><\/span><\/span><\/p>\n

9,6\/8—\u00a0\u00a0n<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>=1,2.<\/b><\/span><\/span><\/span><\/p>\n

b) Observe nas figuras abaixo que o valor m\u00e1ximo fornecido pela escala graduada \u00e9y=x + \u221a2=L.\u221a2\/2 <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

+ \u221a2\u00a0\u00a0—\u00a0Y=12\u221a2\/2 + \u221a2\u00a0\u00a0—\u00a0\u00a0y=7\u221a2cm\u00a0\u00a0—\u00a0\u00a0senr\u2019=7\u221a2\/m=7\u221a2\/\u221a[(7\u221a2)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0+ (\u221a2)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>]\u00a0\u00a0—\u00a0\u00a0senr\u2019=7\u221a2\/10\u00a0\u00a0—<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0\u00a0aplicando Snell-Descartes—\u00a0\u00a0n<\/b><\/span><\/span><\/span>p<\/b><\/span><\/span><\/sub><\/span>.sen45<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>=n.senr\u2019\u00a0\u00a0—\u00a0\u00a01,6.\u221a2\/2=n.7.\u221a2\/10\u00a0\u00a0—\u00a0\u00a0n=1,12\/0,98\u00a0\u00a0—\u00a0\u00a0\u00a0n=1,14.<\/b><\/span><\/span><\/span><\/p>\n

15-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Observe a figura abaixo onde foi tra\u00e7ada a normal N e localizados os respectivos \u00e2ngulos—\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00e2ngulo de incid\u00eancia, i=60<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>—\u00a0\u00a0\u00e2ngulo de refra\u00e7\u00e3o, r=30<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>\u00a0\u00a0—\u00a0\u00a0r<\/b><\/span><\/span><\/span>i<\/b><\/span><\/span><\/sub><\/span>, raio incidente e r<\/b><\/span><\/span><\/span>r<\/b><\/span><\/span><\/sub><\/span>, raio refratado\u00a0\u00a0—\u00a0\u00a0aplicando a lei de Snell-Descartes\u00a0\u00a0—<\/b><\/span><\/span><\/span><\/p>\n

n<\/b><\/span><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/span>.sen60<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>=n.sen30<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>\u00a0\u00a0—\u00a0\u00a01. \u221a3\/2 = n.1\/2—\u00a0\u00a0n=\u221a3\u00a0\u00a0—\u00a0\u00a0R- C.<\/b><\/span><\/span><\/span><\/p>\n

<\/a><\/p>\n

16-<\/b><\/span><\/span><\/span> <\/b>O \u00edndice de refra\u00e7\u00e3o \u00e9 uma medida da capacidade que o meio possui de desviar a luz—\u00a0\u00a0assim, quanto maior for este \u00edndice para um meio mais um raio de luz ser\u00e1 desviado por ele. Por exemplo, a luz ao passar do ar para o olho atravessa por meios (c\u00f3rnea, os l\u00edquidos dentro do olho e o cristalino) cujo \u00edndice de refra\u00e7\u00e3o \u00e9 maior que o do ar, fazendo com que a luz seja bem desviada.\u00a0\u00a0—quanto mais refringente um meio, maior \u00e9 seu \u00edndice de refra\u00e7\u00e3o e o \u00edndice de refra\u00e7\u00e3o de qualquer meio \u00e9 maior que o do v\u00e1cuo (aproximadamente igual ao do ar e vale 1)\u00a0\u00a0—\u00a0\u00a0portanto os \u00edndices de refra\u00e7\u00e3o da c\u00f3rnea e da \u00e1gua s\u00e3o maiores que o do ar\u00a0\u00a0— como, dentro da \u00e1gua ele enxerga a imagem desfocada, os\u00a0<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

desvios produzidos na luz pelas mesmas s\u00e3o muito pequenos e pr\u00f3ximos\u00a0\u00a0—\u00a0\u00a0consequentemente nc\u00f3rnea\u2248n<\/b><\/span><\/span><\/span>\u00e1gua>nar<\/b><\/span><\/span><\/sub><\/span>\u00a0\u00a0—<\/b><\/span><\/span><\/span><\/p>\n

R- D.\u00a0\u00a0—\u00a0\u00a0Observa\u00e7\u00e3o: pesquisando encontrei\u00a0\u00a0—\u00a0\u00a0n<\/b><\/span><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/span>=1; n<\/b><\/span><\/span><\/span>c\u00f3rnea<\/b><\/span><\/span><\/sub><\/span>=1,38 e n<\/b><\/span><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub><\/span>=1,33.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

17-<\/b><\/span><\/span><\/span> Observe nas\u00a0figuras A e B onde foram tra\u00e7ados raios de luz (em vermelho)\u00a0que, quando eles se refratam\u00a0do ar (menos refringente) para a \u00e1gua (mais refringente)\u00a0eles se\u00a0aproximam da normal (em amarelo)\u00a0e apenas a\u00a0figura A satisfaz,\u00a0pois nela os raios de luz chegam aos olhos do vigia..<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A\u00a0figura C tamb\u00e9m n\u00e3o satisfaz, pois quando os raios de luz\u00a0incidem perpendicularmente \u00e0 superf\u00edcie de separa\u00e7\u00e3o\u00a0eles se refratam sem sofrer desvio\u00a0com a imagem da TV n\u00e3o atingindo os olhos do observador.<\/b><\/span><\/span><\/span><\/p>\n

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

 <\/p>\n

Voltar para os exerc\u00edcios<\/span><\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

Resolu\u00e7\u00f5es comentadas dos exerc\u00edcios de vestibulares sobre Refra\u00e7\u00e3o da Luz 01- Durante o dia predomina a refra\u00e7\u00e3o (luz externa mais intensa) e a noite a reflex\u00e3o(luz interna mais intensa 02-\u00a0a) No ar (fora e dentro da esfera), a velocidade do raio de luz \u00e9 de 3,0.1010cm\/s e no vidro de \u00edndice de refra\u00e7\u00e3o nV=1,5 vale nV=C\/VV\u00a0 —\u00a0 1,5=3.1010\/VV\u00a0 —\u00a0 VV=2,0.1010cm\/s\u00a0<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2587,"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-2589","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2589","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=2589"}],"version-history":[{"count":2,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2589\/revisions"}],"predecessor-version":[{"id":10988,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2589\/revisions\/10988"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2587"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2589"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}