{"id":2242,"date":"2016-05-23T23:53:36","date_gmt":"2016-05-23T23:53:36","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2242"},"modified":"2024-09-02T14:21:53","modified_gmt":"2024-09-02T14:21:53","slug":"leis-da-refracao-resolucao","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/optica\/optica-geometrica\/leis-da-refracao\/leis-da-refracao-resolucao\/","title":{"rendered":"Leis da Refra\u00e7\u00e3o – Resolu\u00e7\u00e3o"},"content":{"rendered":"

Resolu\u00e7\u00e3o comentada dos exerc\u00edcios de vestibulares sobre <\/b><\/span><\/span><\/span><\/p>\n

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

01-<\/b><\/span><\/span><\/span> <\/b>(01) Verdadeira, ao passar do ar para a \u00e1gua o raio de luz sofre desvio se aproximando da normal, pois n<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>>n<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/p>\n

(02) Verdadeira, ao passar da \u00e1gua para o ar o raio de luz sofre desvio se afastando da normal, pois n<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>\u00a0>n<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/p>\n

(04) Errada, s\u00e3o leis da refra\u00e7\u00e3o<\/b><\/span><\/span><\/p>\n

(08) Errada, nesse caso ocorre apenas refra\u00e7\u00e3o<\/b><\/span><\/span><\/p>\n

(16) Correta, pois B\u2019 \u00e9 a imagem de B, obtida no prolongamento dos raios luminosos e, portanto n\u00e3o \u00e9 real\u00a0\u00a0<\/b><\/span><\/span><\/p>\n

R-01 +02 +16=19<\/b><\/span><\/span><\/p>\n

02-<\/b><\/span><\/span><\/span> <\/b>(01) Verdadeira \u2013 n e V s\u00e3o inversamente proporcionais<\/b><\/span><\/span><\/p>\n

(02) Falsa \u2013 quando a luz sofre refra\u00e7\u00e3o em dois meios diferentes, ela deve sofrer desvio, a n\u00e3o ser que incida perpendicularmente \u00e0 superf\u00edcie de separa\u00e7\u00e3o.<\/b><\/span><\/span><\/p>\n

(04) Verdadeira, em B, ao passar do ar para a \u00e1gua se aproxima da normal e da \u00e1gua para o ar, se afasta da normal\u00a0 —\u00a0 em C, incid\u00eancia normal \u00e0 superf\u00edcie de separa\u00e7\u00e3o, n\u00e3o sofre desvio.<\/b><\/span><\/span><\/p>\n

(08) Falsa \u2013 em D, ao passar da \u00e1gua para o ar deveria sofrer desvio.<\/b><\/span><\/span><\/p>\n

(16) Falsa, deveria sofrer desvio em A<\/b><\/span><\/span><\/p>\n

(32) Verdadeira, veja justificativas anteriores.\u00a0<\/b><\/span><\/span><\/p>\n

1 + 4 + 32 = 37<\/b><\/span><\/span><\/p>\n

03-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>R- B\u00a0 (veja teoria)<\/b><\/span><\/span><\/p>\n

04-<\/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 nas camadas superiores. Como consequ\u00eancia, a luz proveniente de um astro, como por exemplo, o Sol, sofre desvio se aproximando da normal at\u00e9 atingir os olhos do observador que tem a impress\u00e3o de que ele est\u00e1 acima de sua posi\u00e7\u00e3o real.<\/b><\/span><\/span><\/p>\n

05-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>R- C – Como a atmosfera \u00e9 mais densa nas camadas inferiores, nelas o \u00edndice de refra\u00e7\u00e3o \u00e9 maior que nas camadas superiores e o raio de luz, a medida que desce vai se aproximando da normal.<\/b><\/span><\/span><\/p>\n

06-<\/b><\/span><\/span><\/span> <\/b>O Sol em contato com o solo deixa o ar mais quente e consequentemente menos refringente que o ar das camadas superiores. Isso faz com que os raios de luz sofram reflex\u00e3o total em camadas pr\u00f3ximas ao solo, subam e atinjam os olhos de um observador, que ter\u00e1 a impress\u00e3o de que no solo existe um espelho fornecendo a imagem do objeto. R- B<\/b><\/span><\/span><\/p>\n

07-<\/b><\/span><\/span><\/span>\u00a0\u00a0<\/b><\/span><\/span><\/span>R- B\u00a0 —\u00a0 Observe a figura\u00a0 —\u00a0 menor \u00e2ngulo com a normal, maior ser\u00e1 o \u00edndice de refra\u00e7\u00e3o n.<\/b><\/span><\/span><\/p>\n

08-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Quando\u00a0<\/b><\/span><\/span>\u03bb<\/b><\/span><\/span><\/span>=44nm \u2013 n=1,47\u00a0 —\u00a0 n<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>.sen30<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>=n<\/b><\/span><\/span>q<\/b><\/span><\/span><\/sub>.sen\u03b8\u00a0 —\u00a0 1.0,5=1,47.sen\u03b8\u00a0 —\u00a0 sen\u03b8=0,340\u00a0\u00a0R- C<\/b><\/span><\/span><\/p>\n

09-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>n<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>.sen49<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>=n<\/b><\/span><\/span>v<\/b><\/span><\/span><\/sub>.senr\u00a0 —\u00a0 1.0,75=1,5.senr\u00a0 —\u00a0 senr=1\/2\u00a0 —\u00a0 r=30<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0 o \u00e2ngulo pedido (\u00e2ngulo que o feixe luminoso refratado forma<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

com a dire\u00e7\u00e3o do feixe incidente) corresponde ao desvio na refra\u00e7\u00e3o e vale d=(49 \u2013 30)=19\u00a0 —\u00a0 d=19<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>\u00a0\u00a0R- B<\/b><\/span><\/span><\/p>\n

10-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>senr\/seni =V<\/b><\/span><\/span>vidro<\/b><\/span><\/span><\/sub>\/V<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>\u00a0 —\u00a0 senr\/0,87=1,73.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>\/3.10<\/b><\/span><\/span>8\u00a0\u00a0<\/b><\/span><\/span><\/sup>—\u00a0 senr=0,5017\u22480,5\u00a0 —\u00a0\u00a0r=30<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>\u00a0 R- D\u00a0<\/b><\/span><\/span><\/p>\n

11-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>n<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>.sen60<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>=n<\/b><\/span><\/span>m.<\/b><\/span><\/span><\/sub>sen (180 \u2013 150)\u00a0 —\u00a0 1.\u221a3\/2=n<\/b><\/span><\/span>m<\/b><\/span><\/span><\/sub>.0,5\u00a0 — n<\/b><\/span><\/span>m<\/b><\/span><\/span><\/sub>=\u221a3\u00a0 e o desvio d, que \u00e9 o \u00e2ngulo entre o prolongamento do raio incidente e o raio refratado vale d=30<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>\u00a0 (veja figura abaixo).<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

12-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Veja a figura abaixo:<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

n<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>.sen60<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>=n<\/b><\/span><\/span>P<\/b><\/span><\/span><\/sub>.sen30<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0 1.\u221a3\/2=n<\/b><\/span><\/span>P<\/b><\/span><\/span><\/sub>.1\/2\u00a0 —\u00a0 n<\/b><\/span><\/span>P<\/b><\/span><\/span><\/sub>=\u221a3=1,7<\/b><\/span><\/span><\/p>\n

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

Observe no gr\u00e1fico que o cubo tem\u00a0aresta a=(50 \u2013 30).10<\/b><\/span><\/span>-2<\/b><\/span><\/span><\/sup>=20.10<\/b><\/span><\/span>-2<\/b><\/span><\/span><\/sup>m =2.10<\/b><\/span><\/span>-1<\/b><\/span><\/span><\/sup>m e que a luz demora t=(2 \u2013 1).10<\/b><\/span><\/span>-9<\/b><\/span><\/span><\/sup>s=10<\/b><\/span><\/span>-9<\/b><\/span><\/span><\/sup>s para atravess\u00e1-lo.<\/b><\/span><\/span>\"\"<\/p>\n

Velocidade da luz no meio exterior ao cubo\u00a0 —\u00a0 V<\/b><\/span><\/span>e<\/b><\/span><\/span><\/sub>=d\/t=30.10<\/b><\/span><\/span>-2<\/b><\/span><\/span><\/sup>\/1.10<\/b><\/span><\/span>-9<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0 V<\/b><\/span><\/span>e<\/b><\/span><\/span><\/sub>=3.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>m\/s\u00a0 —\u00a0 velocidade da luz no interior do cubo\u00a0 —\u00a0 V<\/b><\/span><\/span>i<\/b><\/span><\/span><\/sub>=a\/t=2.10<\/b><\/span><\/span>-1<\/b><\/span><\/span><\/sup>\/10<\/b><\/span><\/span>-9<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0 V<\/b><\/span><\/span>i<\/b><\/span><\/span><\/sub>=2.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>m\/s\u00a0 —\u00a0 o meio mais refringente \u00e9 o cubo, pois nele a luz tem menor velocidade\u00a0 —\u00a0 n<\/b><\/span><\/span>e<\/b><\/span><\/span><\/sub>\/n<\/b><\/span><\/span>i<\/b><\/span><\/span><\/sub>=V<\/b><\/span><\/span>i<\/b><\/span><\/span><\/sub>\/V<\/b><\/span><\/span>e<\/b><\/span><\/span><\/sub>=2.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>\/3.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0\u00a0n<\/b><\/span><\/span>e<\/b><\/span><\/span><\/sub>\/n<\/b><\/span><\/span>i<\/b><\/span><\/span><\/sub>=1,5<\/b><\/span><\/span><\/p>\n

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

14-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>sen i=cateto oposto\/hipotenusa=4\/R\u00a0 —\u00a0 sen r=6\/R\u00a0 —\u00a0 n<\/b><\/span><\/span>1<\/b><\/span><\/span><\/sub>.sen i=n<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sub>.sen r\u00a0 —\u00a0 n<\/b><\/span><\/span>1<\/b><\/span><\/span><\/sub>.4\/R=n<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sub>.6\/R\u00a0 —\u00a0\u00a0n<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sub>\/n<\/b><\/span><\/span>1<\/b><\/span><\/span><\/sub>=2\/3\u00a0 R- A<\/b><\/span><\/span><\/p>\n

15-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Observe que os \u00e2ngulos de incid\u00eancia i=53<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>\u00a0e de reflex\u00e3o r=37<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>\u00a0s\u00e3o complementares (i + r=90<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>) e assim sen i=cos r\u00a0 —\u00a0 tgr =15\/20\u00a0 —\u00a0 tg r =0,75\u00a0 —\u00a0 tg r=senr\/cosr\u00a0 —\u00a0 0,75=senr\/cosr\u00a0 —\u00a0 cosr=senr\/0,75\u00a0 —\u00a0 seni=cosr=senr\/0.75\u00a0 —\u00a0 n<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>.seni=n<\/b><\/span><\/span>l\u00edquido<\/b><\/span><\/span><\/sub>.senr\u00a0 —\u00a0<\/b><\/span><\/span><\/p>\n

1.senr\/0,75=n<\/b><\/span><\/span>l\u00edquido<\/b><\/span><\/span><\/sub>.senr\u00a0 —\u00a0 n<\/b><\/span><\/span>l\u00edquido<\/b><\/span><\/span><\/sub>=1\/0,75=1,33\u00a0\u00a0R- B<\/b><\/span><\/span><\/p>\n

16-<\/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><\/p>\n

\"\"<\/p>\n

Aplicar Pit\u00e1goras no tri\u00e2ngulo APQ e achar AQ\u00a0 —\u00a0 (AQ)<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sup>\u00a0= (AP)<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sup>\u00a0+ (PQ)<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0 (AQ)<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sup>= L<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sup>\u00a0+ (L\/4)<\/b><\/span><\/span>2\u00a0<\/b><\/span><\/span><\/sup>\u00a0\u00a0—\u00a0\u00a0(AQ) =\"\" \u00a0\u00a0 <\/b><\/span><\/span><\/p>\n

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(17)\/17<\/b><\/span><\/span><\/p>\n

Usar 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>l\u00edquido<\/b><\/span><\/span><\/sub>.seni=n<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>.senr\u00a0\u00a0 —\u00a0\u00a0 n.sen45<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>=1.4(\"\" — n.\"\"=4(\"\" —\u00a0\u00a0\u00a0n=4\"\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/p>\n

17-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a)<\/b><\/span><\/span><\/p>\n

n<\/b><\/span><\/span>3<\/b><\/span><\/span><\/sub><n<\/b><\/span><\/span>1<\/b><\/span><\/span><\/sub><n<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sub>\u00a0\u00ae\u00a0n<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sub>>n<\/b><\/span><\/span>3<\/b><\/span><\/span><\/sub><\/p>\n

\"\"<\/p>\n

b) menos refringente (menor \u00edndice de refra\u00e7\u00e3o), se afasta mais da normal \u2013 meio 3<\/b><\/span><\/span><\/p>\n

18-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Veja figura abaixo:<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

senr\/seni=V<\/b><\/span><\/span>vidro<\/b><\/span><\/span><\/sub>\/V<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>\u00a0 — senr\/0,87=1,73.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>\/3.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0 senr=0,5017\u00a0 —\u00a0 R- B=D<\/b><\/span><\/span><\/p>\n

19-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Tra\u00e7ando a normal:<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

O \u00e2ngulo de incid\u00eancia que \u00e9 o \u00e2ngulo que o raio incidente forma com a normal vale i=(90 \u2013 32)=58\u00a0\u00a0—\u00a0\u00a0 i=58<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0 r=32<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>\u00a0(veja a figura)\u00a0 R- B<\/b><\/span><\/span><\/p>\n

20-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>A luz se propaga entre dois pontos, sofrendo refra\u00e7\u00e3o sem que haja reflex\u00e3o e, no menor tempo poss\u00edvel (princ\u00edpio de Fermat)\u00a0 – R-A<\/b><\/span><\/span><\/p>\n

21-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Por defini\u00e7\u00e3o o desvio angular (d) \u00e9 o \u00e2ngulo entre o\u00a0prolongamento\u00a0do raio incidente e o raio refratado. A normal (N) \u00e9 obtida unindo-se o centro da circunfer\u00eancia C \u00e0 superf\u00edcie de separa\u00e7\u00e3o entre o ar (n<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>=1) e o hemisf\u00e9rio (n<\/b><\/span><\/span>e<\/b><\/span><\/span><\/sub>=\u221a2).<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

O \u00e2ngulo entre a normal (N) e o raio incidente \u00e9 ( i ) e o \u00e2ngulo entre a normal e o raio refratado \u00e9 ( r ), tal que\u00a0 —\u00a0 senr=catetooposto\/hipotenusa=(R\/2)\/R\u00a0 —\u00a0 senr=1\/2\u00a0 —\u00a0 r=30<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0 n<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>.seni=n<\/b><\/span><\/span>e<\/b><\/span><\/span><\/sub>.senr\u00a0 —\u00a0 1.seni=\u221a2.1\/2\u00a0 —\u00a0 seni=\u221a2\/2\u00a0 —\u00a0 i=45<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/p>\n

\"\"<\/p>\n

i=d + r\u00a0 —\u00a0 45=d + 30\u00a0 —\u00a0\u00a0d=15<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/p>\n

22-<\/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>1<\/b><\/span><\/span><\/sub>\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>2<\/b><\/span><\/span><\/sub>. A \u00fanica alternativa que satisfaz \u00e9 a\u00a0C.<\/b><\/span><\/span><\/p>\n

23-<\/b><\/span><\/span><\/span> <\/b>N<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>.sen\u03b8=n<\/b><\/span><\/span>v<\/b><\/span><\/span><\/sub>.senr\u00a0 —\u00a0 1.0,9=1,5.senr\u00a0 —\u00a0 senr=0,6\u00a0 —\u00a0 se senr=0,6\u00a0 —\u00a0\u00a0 cosr=0,8<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

No tri\u00e2ngulo ABC\u00a0 —\u00a0 cosr=AB\/AC\u00a0 —\u00a0 0,8=4\/AC\u00a0 —\u00a0\u00a0AC=5cm\u00a0<\/b><\/span><\/span><\/p>\n

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

\"\"<\/p>\n

25-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) n<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>=c\/v<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>\u00a0 —\u00a0 1,3=3.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>\/V<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>\u00a0 —\u00a0\u00a0V<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>\u2248 2,3.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>m\/s<\/b><\/span><\/span><\/p>\n

b) Observe na figura\u00a0 —\u00a0 cos50<\/b><\/span><\/span>o<\/b><\/span><\/span><\/sup>=d\/d<\/b><\/span><\/span>p<\/b><\/span><\/span><\/sub>\u00a0 —\u00a0 0,64=1,6\/d<\/b><\/span><\/span>p<\/b><\/span><\/span><\/sub>\u00a0 —\u00a0 d<\/b><\/span><\/span>p<\/b><\/span><\/span><\/sub>=2,5m\u00a0 —\u00a0 sendo a velocidade da radia\u00e7\u00e3o Cerenkov constante\u00a0 —<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0V<\/b><\/span><\/span>p<\/b><\/span><\/span><\/sub>=\u0394S\/\u0394t\u00a0 —\u00a0\u00a0 V<\/b><\/span><\/span>p<\/b><\/span><\/span><\/sub>=d<\/b><\/span><\/span>p<\/b><\/span><\/span><\/sub>\/\u0394t\u00a0 —\u00a0 a radia\u00e7\u00e3o Cerenkov percorre a dist\u00e2ncia d<\/b><\/span><\/span>p<\/b><\/span><\/span><\/sub>\u00a0no mesmo intervalo de tempo em que a luz percorre a dist\u00e2ncia d nesse meio\u00a0 —\u00a0 V<\/b><\/span><\/span>p<\/b><\/span><\/span><\/sub>=2,5\/12.10<\/b><\/span><\/span>-9<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0V<\/b><\/span><\/span>p<\/b><\/span><\/span><\/sub>\u22482,1.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>m\/s<\/b><\/span><\/span><\/p>\n

26-<\/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 atmosfera da Terra, v\u00e3o<\/b><\/span><\/span><\/p>\n

\"\"<\/p>\n

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\u00a0R- C<\/b><\/span><\/span><\/p>\n

27-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Falso\u00a0 —\u00a0 n=C\/V\u00a0 —\u00a0 o \u00edndice de refra\u00e7\u00e3o n \u00e9 diferente para cada comprimento de onda \u0443 compreendido entre 450 nm e 550nm.<\/b><\/span><\/span><\/p>\n

b) Falso\u00a0 —\u00a0 V=C=<\/b><\/span><\/span><\/span>\u03bb<\/b><\/span><\/span>f\u00a0 —\u00a0 3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/span><\/sup>=600.10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/span><\/sup>.f\u00a0 —\u00a0 f=5,0.10<\/b><\/span><\/span><\/span>14<\/b><\/span><\/span><\/span><\/sup>\u00a0Hz<\/b><\/span><\/span><\/span><\/p>\n

c) Falso\u00a0 —\u00a0 \u00a0maior \u00edndice de refra\u00e7\u00e3o corresponde ao menor comprimento de onda, portanto \u00e0 maior frequ\u00eancia.\u00a0<\/b><\/span><\/span><\/p>\n

d) Verdadeiro\u00a0 —\u00a0 n=C\/V\u00a0 —\u00a0 1,2=3.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>\/V\u00a0 —\u00a0 V=2,5.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>m\/s<\/b><\/span><\/span><\/p>\n

e) Falso\u00a0 —\u00a0 n=C\/V\u00a0 —\u00a0 C=constante=n.V\u00a0 —\u00a0 n e V s\u00e3o inversamente proporcionais.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/p>\n

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

 <\/p>\n

28-<\/b><\/span><\/span><\/span> <\/b>I. Falsa\u00a0 —\u00a0 a frequ\u00eancia \u00e9 caracter\u00edstica da onda (luz)\u00a0 —\u00a0 ela \u00e9 sempre a mesma para cada cor, independente do meio onde estiver se propagando.<\/b><\/span><\/span><\/p>\n

II. Falsa\u00a0 —\u00a0 veja justificativa da I.<\/b><\/span><\/span><\/p>\n

III. Verdadeira\u00a0 — a frequ\u00eancia permanece a mesma (caracter\u00edstica da onda)\u00a0 —\u00a0 na \u00e1gua\u00a0 —\u00a0 n<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>=C\/V<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>\u00a0 —\u00a0 4\/3=3.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>\/V<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>\u00a0 — V<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>=9\/4.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>=2,25.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>m\/s\u00a0 —\u00a0 c\u00e1lculo da frequ\u00eancia utilizando o ar\u00a0 —\u00a0\u00a0 V<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>=\u03b3<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>.f<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>\u00a0 —\u00a0 3.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>=6.10<\/b><\/span><\/span>-7<\/b><\/span><\/span><\/sup>.f<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>\u00a0 —\u00a0 f<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>=5.10<\/b><\/span><\/span>14<\/b><\/span><\/span><\/sup>Hz\u00a0 —\u00a0 f<\/b><\/span><\/span>ar<\/b><\/span><\/span><\/sub>=f<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>=constante (independente do meio)\u00a0 —\u00a0 na \u00e1gua\u00a0 —\u00a0 V<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>=\u03b3<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>.f\u00a0 —\u00a0 2,25.10<\/b><\/span><\/span>8<\/b><\/span><\/span><\/sup>= \u03b3<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>.5.10<\/b><\/span><\/span>14<\/b><\/span><\/span><\/sup>\u00a0 —\u00a0 \u03b3<\/b><\/span><\/span>\u00e1gua<\/b><\/span><\/span><\/sub>=4,5.10<\/b><\/span><\/span>-7<\/b><\/span><\/span><\/sup>m.<\/b><\/span><\/span><\/p>\n

IV. Falsa\u00a0 —\u00a0 n\u00e3o importa a dist\u00e2ncia entre a fonte de luz e a superf\u00edcie de separa\u00e7\u00e3o, a f n\u00e3o varia, mas V e \u03b3 variam.<\/b><\/span><\/span><\/p>\n

V.\u00a0 Falsa\u00a0 —\u00a0 Falsa\u00a0 —\u00a0 veja I, II, III e IV.<\/b><\/span><\/span><\/p>\n

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

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

\"\"<\/p>\n

desvio d vale\u00a0 —\u00a0 d= i \u2013 r\u00a0\u00a0 —\u00a0 aplicando a lei de Snell\u00a0 —\u00a0 n<\/b><\/span><\/span>1<\/b><\/span><\/span><\/sub>.seni =n<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sub>.senr\u00a0 —\u00a0 1.seni = n<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sub>.senr\u00a0 —\u00a0 senr=seni\/n<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sub>\u00a0 —\u00a0 essa express\u00e3o indica que n<\/b><\/span><\/span>2<\/b><\/span><\/span><\/sub>\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>2<\/b><\/span><\/span><\/sub>\u00a0for o menor poss\u00edvel\u00a0 —\u00a0\u00a0 consultando a tabela, o menor \u00edndice de refra\u00e7\u00e3o \u00e9 o da \u00e1gua\u00a0 —\u00a0\u00a0R- A<\/b><\/span><\/span><\/p>\n

 <\/p>\n

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

Resolu\u00e7\u00e3o comentada dos exerc\u00edcios de vestibulares sobre Leis da Refra\u00e7\u00e3o 01- (01) Verdadeira, ao passar do ar para a \u00e1gua o raio de luz sofre desvio se aproximando da normal, pois n\u00e1gua>nar (02) Verdadeira, ao passar da \u00e1gua para o ar o raio de luz sofre desvio se afastando da normal, pois n\u00e1gua\u00a0>nar (04) Errada, s\u00e3o leis da refra\u00e7\u00e3o (08)<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2237,"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-2242","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2242","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=2242"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2242\/revisions"}],"predecessor-version":[{"id":10947,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2242\/revisions\/10947"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2237"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2242"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}