{"id":2482,"date":"2016-09-18T22:16:40","date_gmt":"2016-09-18T22:16:40","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2482"},"modified":"2024-08-21T13:39:26","modified_gmt":"2024-08-21T13:39:26","slug":"resolucoes-comentadas-dos-exercicios-de-vestibulares-sobre-efeito-fotoeletrico","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/fisica-moderna\/efeito-fotoeletrico-2\/resolucoes-comentadas-dos-exercicios-de-vestibulares-sobre-efeito-fotoeletrico\/","title":{"rendered":"Efeito Fotoel\u00e9trico – Resolu\u00e7\u00e3o"},"content":{"rendered":"

\u00a0<\/span>Resolu\u00e7\u00f5es comentadas dos exerc\u00edcios de vestibulares sobre<\/b><\/span><\/span><\/span><\/p>\n

Efeito Fotoel\u00e9trico<\/b><\/span><\/span><\/span><\/p>\n

01- R- B<\/b><\/span><\/span><\/span>\u00a0 <\/b><\/span><\/span><\/span>—\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

02-<\/b><\/span><\/span><\/span> <\/b>R- E\u00a0<\/b><\/span><\/span><\/span>\u00a0—\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

03-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Falsa\u00a0 —\u00a0 a massa de um el\u00e9tron vale aproximadamente m=9,11.10-28g.<\/b><\/span><\/span><\/span><\/p>\n

b) Correta\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

c) Falsa\u00a0 —\u00a0 as massas dos pr\u00f3tons e dos n\u00eautrons s\u00e3o praticamente iguais.<\/b><\/span><\/span><\/span><\/p>\n

d) Falsa\u00a0 —\u00a0 existe a dualidade onda- part\u00edcula.<\/b><\/span><\/span><\/span><\/p>\n

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

04-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>I- Correta\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>c<\/b><\/span><\/span><\/sub><\/span>=0\u00a0 —\u00a0 W=hf\u00a0 —\u00a0 observe que a energia cedida ao el\u00e9tron pelo f\u00f3ton incidente \u00e9 a energia que ele precisa receber para ser arrancado pelo metal<\/b><\/span><\/span><\/span><\/p>\n

II- Falsa\u00a0 —\u00a0 a freq\u00fc\u00eancia influencia (freq\u00fc\u00eancia de corte – f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>)<\/b><\/span><\/span><\/span><\/p>\n

III- Falsa\u00a0 —\u00a0 a temperatura do metal n\u00e3o influi na emiss\u00e3o de el\u00e9trons.<\/b><\/span><\/span><\/span><\/p>\n

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

05-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Toda radia\u00e7\u00e3o eletromagn\u00e9tica (luz) se propaga de maneira descont\u00ednua em forma de \u201cpacotes\u201d que recebem o nome de f\u00f3tons \u201cquantum\u201d, conceito de energia quantizada\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>R- 05<\/b><\/span><\/span><\/span><\/p>\n

06<\/b><\/span><\/span><\/span>–\u00a0<\/b><\/span><\/span><\/span>E=h.f\u00a0 —\u00a0 como h \u00e9 a constante de Planck, a energia do f\u00f3ton E \u00e9 diretamente proporcional \u00e0 freq\u00fc\u00eancia f\u00a0 —\u00a0 quanto maior f, maior ser\u00e1 E\u00a0 —<\/b><\/span><\/span><\/span>\u00a0 R- A<\/b><\/span><\/span><\/span><\/p>\n

07-<\/b><\/span><\/span><\/span> <\/b>R- A<\/b><\/span><\/span><\/span>\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

08-<\/b><\/span><\/span><\/span> <\/b>R- C<\/b><\/span><\/span><\/span>\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

09-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Maior freq\u00fc\u00eancia, maior n\u00edvel de energia\u00a0 —\u00a0 a energia cin\u00e9tica dos f\u00f3tons emitidos \u00e9 a mesma e consequentemente a velocidade \u00e9 a mesma\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- A<\/b><\/span><\/span><\/span><\/p>\n

10-<\/b><\/span><\/span><\/span> <\/b>R- C<\/b><\/span><\/span><\/span>\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

11-<\/b><\/span><\/span><\/span> <\/b>R- A\u00a0<\/b><\/span><\/span><\/span>\u00a0—\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

12<\/b><\/span><\/span><\/span>– R- C\u00a0<\/b><\/span><\/span><\/span>\u00a0—\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

13-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Falsa\u00a0 —\u00a0 o potencial de corte \u00e9 o mesmo qualquer que seja a intensidade da luz incidente.<\/b><\/span><\/span><\/span><\/p>\n

b) Falsa\u00a0 —\u00a0 a energia cin\u00e9tica m\u00e1xima \u00e9 fornecida por K<\/b><\/span><\/span><\/span>m<\/b><\/span><\/span><\/sub><\/span>=e.V<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0(e \u2013 carga de um el\u00e9tron e V<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0\u2013 potencial de corte)<\/b><\/span><\/span><\/span><\/p>\n

c) Correta\u00a0 —\u00a0 \u00e9 o f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0do gr\u00e1fico (freq\u00fc\u00eancia de corte)<\/b><\/span><\/span><\/span><\/p>\n

d) Falsa\u00a0 — Falsa\u00a0 —\u00a0 veja b<\/b><\/span><\/span><\/span><\/p>\n

R- C\u00a0<\/b><\/span><\/span><\/span><\/p>\n

14-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Voc\u00ea est\u00e1 aumentando a quantidade de f\u00f3tons emitidos pela l\u00e2mpada\u00a0 —<\/b><\/span><\/span><\/span>\u00a0 R- D<\/b><\/span><\/span><\/span><\/p>\n

15-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) As energias dos f\u00f3tons que surgiram foram obtidas atrav\u00e9s das massas do el\u00e9tron e do p\u00f3sitron que desapareceram no processo de aniquila\u00e7\u00e3o.A rela\u00e7\u00e3o entre massas e energias foram previstas pela teoria da relatividade de Einstein na equa\u00e7\u00e3o E=mC<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>, onde m \u00e9 a quantidade de massas convertidas em energia e C a velocidade da luz no v\u00e1cuo, de valor C=3,0.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>ms.<\/b><\/span><\/span><\/span><\/p>\n

b) A energia de um f\u00f3ton (E) e a sua frequ\u00eancia (f) est\u00e3o relacionadas pela express\u00e3o E = h . f, em que h \u00e9 a constante de Planck\u00a0 —\u00a0 igualando as energias dos dois f\u00f3tons ao equivalente em energia das massas das part\u00edculas aniquiladas (el\u00e9tron e p\u00f3sitron)\u00a0 —\u00a0\u00a0 \u00a0<\/b><\/span><\/span><\/span><\/p>\n

E<\/b><\/span><\/span><\/span>f\u00f3tons<\/b><\/span><\/span><\/sub><\/span>\u00a0= E<\/b><\/span><\/span><\/span>massas equivalentes<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 \u00a02.(h.f) = 2.M<\/b><\/span><\/span><\/span>el\u00e9tron<\/b><\/span><\/span><\/sub><\/span>\u00a0.C<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0\u00a0—\u00a0 6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>.f=9,1.10<\/b><\/span><\/span><\/span>-31<\/b><\/span><\/span><\/sup><\/span>.(3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0f=1,2.10<\/b><\/span><\/span><\/span>20<\/b><\/span><\/span><\/sup><\/span>Hz<\/b><\/span><\/span><\/span><\/p>\n

16-<\/b><\/span><\/span><\/span> <\/b>R- E<\/b><\/span><\/span><\/span>\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

17-<\/b><\/span><\/span><\/span> <\/b>R- (01 + 02 + 04 + 16)=23<\/b><\/span><\/span><\/span>\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

18-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Com o decorrer do tempo o el\u00e9tron vai adquirindo mais energia o que faz aumentar a sua velocidade at\u00e9 que ele atinja a velocidade da luz (3,0.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>m\/s) e, a partir da\u00ed ele prossegue com essa velocidade que \u00e9 o valor A do gr\u00e1fico.<\/b><\/span><\/span><\/span><\/p>\n

b) E=h.f\u00a0 —\u00a0 c=\u03bbf\u00a0 —\u00a0 f=c\/\u03bb\u00a0 —\u00a0 mc<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>=hf\u00a0 —\u00a0 mc<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>=hc\/\u03bb\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0\u03bb=h\/mc\u00a0<\/b><\/span><\/span><\/span>\u00a0—\u00a0 mc=Q\u00a0 —\u00a0 25.10<\/b><\/span><\/span><\/span>-18<\/b><\/span><\/span><\/sup><\/span>=6.6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>\/Q\u00a0 —\u00a0 Q=6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>\/25.10<\/b><\/span><\/span><\/span>-18<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>Q=2,64.10<\/b><\/span><\/span><\/span>-15<\/b><\/span><\/span><\/sup><\/span>\u00a0kg.ms<\/b><\/span><\/span><\/span><\/p>\n

19-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Quanto maior a freq\u00fc\u00eancia da luz incidente (menor comprimento de onda) maior ser\u00e1 seu n\u00edvel energ\u00e9tico facilitando a retirada de el\u00e9trons (emiss\u00e3o de luz)\u00a0 —\u00a0 a luz verde tema maior freq\u00fc\u00eancia que a vermelha\u00a0 e consequentemente cada f\u00f3ton verde tem mais energia que cada f\u00f3ton vermelho\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- B<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

20-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>E=\u03bbf\u00a0 —\u00a0 c=\u03bbf\u00a0 —\u00a0 E=h.c\/\u03bb=6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>.3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\/600.10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 E=3,3.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>J\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>R- C<\/b><\/span><\/span><\/span><\/p>\n

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

\"\"<\/p>\n

Observe na tabela ao lado que a freq\u00fc\u00eancia e consequentemente o n\u00edvel de energia dos f\u00f3tons aumenta do vermelho para o violeta<\/b><\/span><\/span><\/span><\/p>\n

—\u00a0<\/b><\/span><\/span><\/span>\u00a0R- B<\/b><\/span><\/span><\/span><\/p>\n

22-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>A energia da radia\u00e7\u00e3o incidente\u00a0 (f\u00f3ton) \u00e9 dada por\u00a0 E=h.f\u00a0 —\u00a0 h \u2013 constante de Planck e f freq\u00fc\u00eancia do f\u00f3ton incidente\u00a0 —<\/b><\/span><\/span><\/span><\/p>\n

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

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

\"\"<\/p>\n

\"\"<\/p>\n

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

24-<\/b><\/span><\/span><\/span> <\/b>R- E<\/b><\/span><\/span><\/span>\u00a0 —\u00a0 veja teoria<\/b><\/span><\/span><\/span><\/p>\n

25-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>E<\/b><\/span><\/span><\/span>cm\u00e1x<\/b><\/span><\/span><\/sub><\/span>=h.f \u2013 W\u00a0 —\u00a0 3,6.1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>=6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>.f \u2013 3.1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 5,76.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>=6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>f\u00a0 —\u00a0 f=1,6.1015 Hz\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- A<\/b><\/span><\/span><\/span><\/p>\n

26-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>01. Correta\u00a0 —\u00a0 como a freq\u00fc\u00eancia da luz violeta \u00e9 maior que da luz vermelha, o \u201cf\u00f3ton violeta\u201d \u00e9 mais energ\u00e9tico que o \u201cf\u00f3ton vermelho\u201d<\/b><\/span><\/span><\/span><\/p>\n

02. Correta\u00a0 —\u00a0 a difra\u00e7\u00e3o \u00e9 junto com a interfer\u00eancia um fen\u00f4meno tipicamente ondulat\u00f3rio\u00a0 —\u00a0 a difra\u00e7\u00e3o \u00e9 observada quando uma onda muda de dire\u00e7\u00e3o devido a um obst\u00e1culo cujas dimens\u00f5es s\u00e3o compar\u00e1veis ao comprimento de onda\u00a0 —\u00a0 a interfer\u00eancia luminosa consiste no fato de 2 ondas, por exemplo, se movendo em sentidos contr\u00e1rios sofrem interfer\u00eancia produzindo uma onda resultante.\u00a0<\/b><\/span><\/span><\/span>\"\"<\/p>\n

04. Correta\u00a0 —\u00a0 veja teoria.<\/b><\/span><\/span><\/span><\/p>\n

08. Correta\u00a0 —\u00a0 trata-se da natureza dual da luz, ora como onda e ora como part\u00edcula.<\/b><\/span><\/span><\/span><\/p>\n

16- Falsa\u00a0 —\u00a0 veja 08.<\/b><\/span><\/span><\/span><\/p>\n

R- ( 01 + 02+ + 04 + 08)=15<\/b><\/span><\/span><\/span><\/p>\n

27-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>E=h.f\u00a0 —\u00a0 E=m.C<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 m.C<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>=h.f\u00a0 —\u00a0 mC=Q=h.fC\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- C<\/b><\/span><\/span><\/span>
\n<\/b><\/span><\/span><\/span><\/p>\n

28-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>As naturezas ondulat\u00f3ria e corpuscular da luz s\u00e3o complementares e n\u00e3o antag\u00f4nicas\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- B<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

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

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

\"\"<\/p>\n

31-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>As op\u00e7\u00f5es (a), (b) e (d) apresentam fen\u00f4menos exclusivamente ondulat\u00f3rios. Somente a op\u00e7\u00e3o (b) apresenta fen\u00f4menos de caracter\u00edsticas corpusculares (efeito fotoel\u00e9trico) e ondulat\u00f3rias (difra\u00e7\u00e3o)\u00a0 \u00a0<\/b><\/span><\/span><\/span><\/p>\n

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

32-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>E<\/b><\/span><\/span><\/span>cin.m\u00e1x.<\/b><\/span><\/span><\/sub><\/span>=h.f \u2013 W\u00a0 —\u00a0 C=<\/b><\/span><\/span><\/span>\u03bb<\/b><\/span><\/span><\/span><\/span>f\u00a0 —\u00a0 f=C\/\u03bb\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>cin.m\u00e1x.<\/b><\/span><\/span><\/sub><\/span>=h.C\/\u03bb \u2013 W=6,63.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>.3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\/327.10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>\u00a0\u2013 1,8.1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>cin.m\u00e1x.<\/b><\/span><\/span><\/sub><\/span>=3,8 \u2013 1,8\u00a0 —\u00a0<\/b><\/span><\/span><\/span><\/p>\n

E<\/b><\/span><\/span><\/span>cin.m\u00e1x.<\/b><\/span><\/span><\/sub><\/span>=2,0 eV<\/b><\/span><\/span><\/span><\/p>\n

33-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Do gr\u00e1fico, vemos que a frequ\u00eancia limite, ou frequ\u00eancia de corte \u00e9 f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0= 1,2 \u00b4 10<\/b><\/span><\/span><\/span>15<\/b><\/span><\/span><\/sup><\/span>Hz.<\/b><\/span><\/span><\/span><\/p>\n

b) Dada a constante de Planck, h = 6,6 \u00b4 10\u201334 J.s\u00a0 —\u00a0 a equa\u00e7\u00e3o de Einstein para o efeito fotoel\u00e9trico \u00e9\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>cm\u00e1x<\/b><\/span><\/span><\/sub><\/span>\u00a0= h f \u2013 W, sendo: W o trabalho para arrancar um el\u00e9tron; h.f a energia do f\u00f3ton incidente e E<\/b><\/span><\/span><\/span>cm\u00e1x<\/b><\/span><\/span><\/sub><\/span>\u00a0a energia cin\u00e9tica m\u00e1xima com que o el\u00e9tron arrancado \u00e9 ejetado\u00a0 —\u00a0 veja o gr\u00e1fico da energia cin\u00e9tica m\u00e1xima em fun\u00e7\u00e3o da freq\u00fc\u00eancia\u00a0 —\u00a0<\/b><\/span><\/span><\/span><\/p>\n

A constante h \u00e9 o coeficiente angular da reta: h = tg \u00a0\u00a0—\u00a0\u00a0 mas no tri\u00e2ngulo da figura, tg a = W\/f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 \u00a0h =W\/f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 W = h.f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 \u00a0<\/b><\/span><\/span><\/span>\"\"<\/p>\n

assim a equa\u00e7\u00e3o do efeito fotoel\u00e9trico fica\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>cm\u00e1x<\/b><\/span><\/span><\/sub><\/span>\u00a0= h.f \u2013 h.f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0= h(f \u2013 f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>)\u00a0 —\u00a0 para o potencial limite de 1,5 V, podemos tirar do gr\u00e1fico que a frequ\u00eancia \u00e9 de aproximadamente 1,3.10<\/b><\/span><\/span><\/span>15<\/b><\/span><\/span><\/sup><\/span>\u00a0Hz\u00a0 —\u00a0 efetuando os c\u00e1lculos\u00a0 —\u00a0\u00a0 E<\/b><\/span><\/span><\/span>cm\u00e1x<\/b><\/span><\/span><\/sub><\/span>\u00a0= 6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>\u00a0(1,3 \u2013 1,2) 10<\/b><\/span><\/span><\/span>15<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 \u00a0E<\/b><\/span><\/span><\/span>cm\u00e1x<\/b><\/span><\/span><\/sub><\/span>=6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>\u00a0(0,1) 10<\/b><\/span><\/span><\/span>15<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>E<\/b><\/span><\/span><\/span>cm\u00e1x<\/b><\/span><\/span><\/sub><\/span>\u00a0= 6,6.10<\/b><\/span><\/span><\/span>-20<\/b><\/span><\/span><\/sup><\/span>\u00a0J.<\/b><\/span><\/span><\/span><\/p>\n

34-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>A pot\u00eancia da luz\u00a0 —\u00a0 energia por tempo\u00a0 —\u00a0\u00a0 se refere ao n\u00famero de f\u00f3tons que ela \u00e9 capaz de emitir, por segundo\u00a0 —\u00a0 se voc\u00ea compara-las verificar\u00e1 que a mais potente (I) emite muito mais f\u00f3tons por segundo que a (II)\u00a0 —\u00a0 a energia de cada f\u00f3ton \u00e9 fornecida por E=h.c\/\u03bb\u00a0 —\u00a0 como todas grandezas (h \u2013 constante de Planck; c \u2013 velocidade da luz e \u03bb \u2013 comprimento de onda) s\u00e3o os mesmos, a energia de cada f\u00f3ton tamb\u00e9m ser\u00e1 a mesma\u00a0 —\u00a0<\/b><\/span><\/span><\/span>R- A\u00a0<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

35-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>E=h.c\/\u03bb\u00a0 —\u00a0 6.600.1,6.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>=6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>.3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\/\u03bb\u00a0 — \u03bb=1,87.10<\/b><\/span><\/span><\/span>-10<\/b><\/span><\/span><\/sup><\/span>m\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- E<\/b><\/span><\/span><\/span><\/p>\n

36-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Pela conserva\u00e7\u00e3o da quantidade de movimento\u00a0 —\u00a0 \u00a0Q<\/b><\/span><\/span><\/span>antes<\/b><\/span><\/span><\/sub><\/span>\u00a0= Q<\/b><\/span><\/span><\/span>depois<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0\u00a0 m.4.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>\u00a0= m.(-V) + 14.5.10<\/b><\/span><\/span><\/span>6\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 4.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>.m = – m.V + 7.10<\/b><\/span><\/span><\/span>7\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 como o choque \u00e9 perfeitamente el\u00e1stico, devido a conserva\u00e7\u00e3o de energia cin\u00e9tica, o coeficiente de restitui\u00e7\u00e3o \u00e9 igual a 1<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 (velocidade relativa de afastamento)\/(velocidade relativa de aproxima\u00e7\u00e3o) = 1<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 (V + 5.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>)\/(4.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>) = 1<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 V + 5.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\u00a0= 4.10<\/b><\/span><\/span><\/span>7\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 V = 4.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>\u00a0\u2013 5.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\u00a0= 4.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>\u00a0– 0,5.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>\u00a0= 3,5.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>\u00a0m\/s<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 voltando na express\u00e3o da conserva\u00e7\u00e3o da quantidade de movimento\u00a0 —\u00a0 4.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>.m = – m.V + 7.10<\/b><\/span><\/span><\/span>7\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 4.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>.m = – m.3,5.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>\u00a0+ 7.10<\/b><\/span><\/span><\/span>7\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 4.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>.m + 3,5.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>.m = 7.10<\/b><\/span><\/span><\/span>7\u00a0<\/b><\/span><\/span><\/sup><\/span>\u00a0—\u00a0 7,5.m = 7\u00a0 —\u00a0 m = 7\/7,5\u00a0 —\u00a0 \u00a0<\/b><\/span><\/span><\/span>m=0,93 u (unidade de massa at\u00f4mica)<\/b><\/span><\/span><\/span><\/p>\n

\u00a0b) Pela express\u00e3o da energia E = hc\/l\u00a0 —\u00a0 7.10<\/b><\/span><\/span><\/span>12<\/b><\/span><\/span><\/sup><\/span>\u00a0= 4.10<\/b><\/span><\/span><\/span>-15<\/b><\/span><\/span><\/sup><\/span>.3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\/l\u00a0 —\u00a0 l = 12.10<\/b><\/span><\/span><\/span>-7<\/b><\/span><\/span><\/sup><\/span>\/(7.10<\/b><\/span><\/span><\/span>12<\/b><\/span><\/span><\/sup><\/span>)\u00a0\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>\u03bb=1,7.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>\u00a0m<\/b><\/span><\/span><\/span>\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

37-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>A cor \u00e9 uma caracter\u00edstica da luz absorvida e da luz refletida pelos objetos, dependendo ainda da luz incidente sobre eles.<\/b><\/span><\/span><\/span><\/p>\n

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

38-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>(I) Correta\u00a0 —\u00a0\u00a0 conforme prop\u00f4s Einstein, a luz \u00e9 formada de corp\u00fasculos ou quanta de luz, mais tarde denominados f\u00f3tons\u00a0 —\u00a0\u00a0 de acordo com a equa\u00e7\u00e3o de Planck, a energia (E) transportada por um f\u00f3ton \u00e9 diretamente proporcional \u00e0 frequ\u00eancia (f) da radia\u00e7\u00e3o\u00a0 —\u00a0 E = h f, sendo h a constante de Planck.<\/b><\/span><\/span><\/span><\/p>\n

(II) Correta.=\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>cm\u00e1x<\/b><\/span><\/span><\/sub><\/span>=hf \u2013 W\u00a0 —\u00a0 sendo W o trabalho para arrancar um el\u00e9tron do metal.<\/b><\/span><\/span><\/span><\/p>\n

(III) Incorreta.\u00a0 \u00a0<\/b><\/span><\/span><\/span><\/p>\n

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

39-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Sendo a velocidade do el\u00e9tron \u00e9 muito menor que a velocidade da luz, pode-se desconsiderar efeitos relativ\u00edsticos e usar a express\u00e3o convencional da energia cin\u00e9tica.\u00a0 —\u00a0 Ec = h f\u00a0 e\u00a0\u00a0 Ec =mV<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\/2\u00a0 —\u00a0 combinando essas express\u00f5es\u00a0 —\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/b><\/span><\/span><\/span><\/p>\n

h f = mV<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\/2\u00a0 —\u00a0 f=mV<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\/2h=9,11.10<\/b><\/span><\/span><\/span>-31<\/b><\/span><\/span><\/sup><\/span>.(3.10<\/b><\/span><\/span><\/span>7<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\/2.6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>=8,2.10<\/b><\/span><\/span><\/span>-16<\/b><\/span><\/span><\/sup><\/span>\/13.10<\/b><\/span><\/span><\/span>-33<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 f=6,3.10<\/b><\/span><\/span><\/span>17\u00a0<\/b><\/span><\/span><\/sup><\/span>Hz\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>a ordem de grandeza \u00e9 10<\/b><\/span><\/span><\/span>18<\/b><\/span><\/span><\/sup><\/span><\/p>\n

40-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Dados: c = 3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\u00a0m\/s; h = 6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>\u00a0J.s; l = 6.10<\/b><\/span><\/span><\/span>-7<\/b><\/span><\/span><\/sup><\/span>\u00a0m.<\/b><\/span><\/span><\/span><\/p>\n

Lembrando a equa\u00e7\u00e3o fundamental da ondulat\u00f3ria:<\/b><\/span><\/span><\/span><\/p>\n

c = l f\u00a0 — \u00a0f =c\/\u03bb\u00a0 —\u00a0\u00a0 substituindo essa express\u00e3o na equa\u00e7\u00e3o dada\u00a0 —\u00a0 E = h f\u00a0 —\u00a0 E = hc\/\u03bb\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0E = 3.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>\u00a0J.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

b) Dados:\u00a0 i = 45\u00b0; r = 30\u00b0; n<\/b><\/span><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/span>\u00a0= 1.<\/b><\/span><\/span><\/span><\/p>\n

\u00a0Aplicando a Lei de Snell\u00a0 —\u00a0 n<\/b><\/span><\/span><\/span>ar<\/b><\/span><\/span><\/sub><\/span>\u00a0sen 45\u00b0 = n<\/b><\/span><\/span><\/span>X<\/b><\/span><\/span><\/sub><\/span>\u00a0sen 30\u00b0\u00a0 —\u00a0 1.\u221a2\/2=n<\/b><\/span><\/span><\/span>X<\/b><\/span><\/span><\/sub><\/span>.1\/2\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>n<\/b><\/span><\/span><\/span>X<\/b><\/span><\/span><\/sub><\/span>=\u221a2<\/b><\/span><\/span><\/span><\/p>\n

nX =\u00a0\"\"<\/b><\/span><\/span><\/span><\/p>\n

c) Dados: c = 3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\u00a0m\/s\u00a0 —\u00a0 da defini\u00e7\u00e3o de \u00edndice de refra\u00e7\u00e3o\u00a0 —\u00a0 n<\/b><\/span><\/span><\/span>X<\/b><\/span><\/span><\/sub><\/span>=c\/V<\/b><\/span><\/span><\/span>X<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 V<\/b><\/span><\/span><\/span>X<\/b><\/span><\/span><\/sub><\/span>=c\/n<\/b><\/span><\/span><\/span>X<\/b><\/span><\/span><\/sub><\/span>=3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\/\u221a2\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>V<\/b><\/span><\/span><\/span>X<\/b><\/span><\/span><\/sub><\/span>=1,5.\u221a2.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\u00a0m\/s<\/b><\/span><\/span><\/span><\/p>\n

41-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>A f\u00edsica cl\u00e1ssica estabelecia que a luz se propagava na forma de ondas e de maneira cont\u00ednua\u00a0 —\u00a0 a f\u00edsica moderna estabeleceu a teoria qu\u00e2ntica, afirmando que a luz n\u00e3o se propaga de forma cont\u00ednua, mas em pequenos \u201cgr\u00e2nulos\u201d chamados f\u00f3tons\u00a0 —\u00a0 ao movimento de cada part\u00edcula est\u00e1 associada uma onda\u00a0 —\u00a0 dependendo do fen\u00f4meno, prevalecem as caracter\u00edsticas ondulat\u00f3rias ou corpusculares, da\u00ed a dualidade entre part\u00edculas e ondas.<\/b><\/span><\/span><\/span><\/p>\n

Por exemplo: quando se faz um feixe de el\u00e9trons atravessar uma fenda, ocorre difra\u00e7\u00e3o, evidenciando o car\u00e1ter ondulat\u00f3rio da mat\u00e9ria\u00a0 —\u00a0 \u00a0quando um feixe de luz de alta frequ\u00eancia incide sobre uma chapa met\u00e1lica, el\u00e9trons podem ser arrancados (efeito fotoel\u00e9trico) explicado por Einstein, considerando a luz como um feixe de part\u00edculas. \u00a0<\/b><\/span><\/span><\/span><\/p>\n

R- C<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

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

\"\"<\/p>\n

43-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) \u00a0m<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0= m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0= 2 g = 2.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>\u00a0kg; c = 3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>\u00a0m\/s\u00a0 —\u00a0 a massa a ser convertida em energia \u00e9 m = m<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\u00a0+ m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0= 4.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>\u00a0kg\u00a0 —\u00a0\u00a0 da equa\u00e7\u00e3o de Einstein, a energia liberada na aniquila\u00e7\u00e3o \u00e9\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>lib<\/b><\/span><\/span><\/sub><\/span>\u00a0= mc<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>lib<\/b><\/span><\/span><\/sub><\/span>\u00a0= 4.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>.(3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>)<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>lib<\/b><\/span><\/span><\/sub><\/span>\u00a0= 4.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>.9.10<\/b><\/span><\/span><\/span>16<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0E<\/b><\/span><\/span><\/span>lib<\/b><\/span><\/span><\/sub><\/span>=3,6.10<\/b><\/span><\/span><\/span>14<\/b><\/span><\/span><\/sup><\/span>\u00a0J<\/b><\/span><\/span><\/span><\/p>\n

b) Dados\u00a0 —\u00a0\u00a0 popula\u00e7\u00e3o\u00a0 —\u00a0\u00a0 1 milh\u00e3o de habitantes\u00a0 —\u00a0 N = 10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\u00a0habitantes\u00a0 —\u00a0 consumo m\u00e9dio\u00a0 —\u00a0 100 kWh\/habitante.m\u00eas\u00a0 —\u00a0<\/b><\/span><\/span><\/span><\/p>\n

lembrando que 1 kWh = 3,6.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\u00a0J, a pot\u00eancia consumida mensalmente pela cidade \u00e9:\u00a0 —\u00a0 \u00a0P<\/b><\/span><\/span><\/span>otcons<\/b><\/span><\/span><\/sub><\/span>\u00a0= 100.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>.3,6.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\u00a0= 360.10<\/b><\/span><\/span><\/span>12<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 \u00a0P<\/b><\/span><\/span><\/span>otcons<\/b><\/span><\/span><\/sub><\/span>=3,6\u00b410<\/b><\/span><\/span><\/span>14<\/b><\/span><\/span><\/sup><\/span>\u00a0J\/m\u00eas\u00a0 —\u00a0 P<\/b><\/span><\/span><\/span>otcons<\/b><\/span><\/span><\/sub><\/span>=E<\/b><\/span><\/span><\/span>lib<\/b><\/span><\/span><\/sub><\/span>\/\u0394t\u00a0 —\u00a0 3,6.10<\/b><\/span><\/span><\/span>14<\/b><\/span><\/span><\/sup><\/span>=3,6.10<\/b><\/span><\/span><\/span>14<\/b><\/span><\/span><\/sup><\/span>\/\u0394t\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>\u0394t=1 m\u00eas<\/b><\/span><\/span><\/span><\/p>\n

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

45-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Energia de um f\u00f3ton\u00a0 —\u00a0 E=h.f\u00a0 —\u00a0 energia transformada por n f\u00f3tons\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>total<\/b><\/span><\/span><\/sub><\/span>=nh.f=400h.f\u00a0 —\u00a0 c=\u03bb.f\u00a0 —\u00a0 E=h.c\/\u03bb\u00a0 —\u00a0 pot\u00eancia\u00a0 —\u00a0 P<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>=E<\/b><\/span><\/span><\/span>total<\/b><\/span><\/span><\/sub><\/span>\/\u0394t\u00a0 —\u00a0 P<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>=400h.c\/\u03bb.\u0394t (I)\u00a0 —\u00a0 intensidade de onda que deve impressionar a retina\u00a0 —\u00a0 I=P<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\/A=P<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\/\u03c0.d<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>(II)\u00a0 —\u00a0 substituindo I em II\u00a0 —\u00a0 I=400h.c\/\u03c0.r<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u03bb\u0394t (III)\u00a0 —\u00a0 intensidade de onda da fonte\u00a0 —\u00a0 I=P<\/b><\/span><\/span><\/span>of<\/b><\/span><\/span><\/sub><\/span>\/4\u03c0d<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0(IV)\u00a0 —\u00a0 igualando III com VI\u00a0 —\u00a0 400h.c\/\u03c0.r<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u03bb\u0394t= P<\/b><\/span><\/span><\/span>of<\/b><\/span><\/span><\/sub><\/span>\/4\u03c0.d<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 d=r\/400.\u221a(P<\/b><\/span><\/span><\/span>of<\/b><\/span><\/span><\/sub><\/span>.\u03bb.\u0394t)\/h.c\u00a0 —\u00a0 observe que, sendo r, P<\/b><\/span><\/span><\/span>of<\/b><\/span><\/span><\/sub><\/span>, \u0394t,h e c constantes, a dist\u00e2ncia d \u00e9 diretamente proporcional ao comprimento de onda \u03bb\u00a0 —\u00a0 como o comprimento de onda da luz vermelha (l<\/b><\/span><\/span><\/span>v<\/b><\/span><\/span><\/sub><\/span>) \u00e9 maior que o da luz azul (l<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sub><\/span>),\u00a0<\/b><\/span><\/span><\/span>a fonte que poder ser vista a uma dist\u00e2ncia maior \u00e9 a que emite luz vermelha.<\/b><\/span><\/span><\/span><\/p>\n

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

46-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Respostas das quest\u00f5es que envolvem f\u00edsica:<\/b><\/span><\/span><\/span><\/p>\n

01) Falsa\u00a0 —\u00a0\u00a0 os \u00e1tomos t\u00eam a capacidade de emitir luz no exato momento em que el\u00e9trons saltam de camadas mais externas para outras mais internas da eletrosfera at\u00f4mica.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

02) Falsa\u00a0 —\u00a0 lentes de bordas grossas com \u00edndice de refra\u00e7\u00e3o maior que o do ar s\u00e3o divergentes.<\/b><\/span><\/span><\/span><\/p>\n

16) Falsa\u00a0 —\u00a0\u00a0 1 quatrilh\u00e3o = 10<\/b><\/span><\/span><\/span>15<\/b><\/span><\/span><\/sup><\/span>\u00a0 — dura\u00e7\u00e3o do pulso\u00a0 —\u00a0 \u2206t=1\/10<\/b><\/span><\/span><\/span>15<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 \u2206t=10<\/b><\/span><\/span><\/span>-15<\/b><\/span><\/span><\/sup><\/span>\u00a0s<\/b><\/span><\/span><\/span><\/p>\n

R-\u00a0<\/b><\/span><\/span><\/span>(04 + 08 + 64) = 76.<\/b><\/span><\/span><\/span><\/p>\n

47-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>P=E\/\u2206t\u00a0 —\u00a0 110.10<\/b><\/span><\/span><\/span>-3<\/b><\/span><\/span><\/sup><\/span>=E\/6.10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>total<\/b><\/span><\/span><\/sub><\/span>=660.10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>J\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>1f\u00f3ton<\/b><\/span><\/span><\/sub><\/span>=hf=6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>.4.10<\/b><\/span><\/span><\/span>14<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>1f\u00f3ton<\/b><\/span><\/span><\/sub><\/span>=26,4.10<\/b><\/span><\/span><\/span>-20<\/b><\/span><\/span><\/sup><\/span>J\u00a0 —\u00a0 n\u00famero de f\u00f3tons\u00a0 —\u00a0 n=E<\/b><\/span><\/span><\/span>total<\/b><\/span><\/span><\/sub><\/span>\/E<\/b><\/span><\/span><\/span>1f\u00f3ton<\/b><\/span><\/span><\/sub><\/span>=660.10<\/b><\/span><\/span><\/span>-12<\/b><\/span><\/span><\/sup><\/span>\/26,4.10<\/b><\/span><\/span><\/span>-20<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 n=25.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>=2,5.10<\/b><\/span><\/span><\/span>9<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- A<\/b><\/span><\/span><\/span><\/p>\n

48-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>Equa\u00e7\u00e3o fundamental da ondulat\u00f3ria\u00a0 —\u00a0 V=c=\u03bbf\u00a0 —\u00a0 3.10<\/b><\/span><\/span><\/span>8<\/b><\/span><\/span><\/sup><\/span>=700.10<\/b><\/span><\/span><\/span>-9<\/b><\/span><\/span><\/sup><\/span>.f\u00a0 —\u00a0 f=3\/7.10<\/b><\/span><\/span><\/span>15<\/b><\/span><\/span><\/sup><\/span>Hz\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>total<\/b><\/span><\/span><\/sub><\/span>=500kcal=5.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>\u00a0cal=5.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>.4\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>total<\/b><\/span><\/span><\/sub><\/span>=2.10<\/b><\/span><\/span><\/span>6\u00a0<\/b><\/span><\/span><\/sup><\/span>J\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>1f\u00f3ton<\/b><\/span><\/span><\/sub><\/span>=hf=6,62.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>.3\/7.10<\/b><\/span><\/span><\/span>15<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 E<\/b><\/span><\/span><\/span>1f\u00f3ton<\/b><\/span><\/span><\/sub><\/span>=2,9.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>J\u00a0 —\u00a0 n\u00famero de f\u00f3tons\u00a0 —\u00a0 n=E<\/b><\/span><\/span><\/span>total<\/b><\/span><\/span><\/sub><\/span>\/E<\/b><\/span><\/span><\/span>1f\u00f3ton<\/b><\/span><\/span><\/sub><\/span>=2.10<\/b><\/span><\/span><\/span>6<\/b><\/span><\/span><\/sup><\/span>\/2,9.10<\/b><\/span><\/span><\/span>-19<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0 n=0,69.10<\/b><\/span><\/span><\/span>25<\/b><\/span><\/span><\/sup><\/span>=6,9.10<\/b><\/span><\/span><\/span>24<\/b><\/span><\/span><\/sup><\/span>\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>R- A<\/b><\/span><\/span><\/span><\/p>\n

49-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>a) Dados\u00a0 — \u00a0\u03bb<\/b><\/span><\/span><\/span>verde<\/b><\/span><\/span><\/sub><\/span>\u00a0= 500 nm\u00a0 — \u00a0\u03bb<\/b><\/span><\/span><\/span>vermelho<\/b><\/span><\/span><\/sub><\/span>\u00a0= 650 nm\u00a0 —\u00a0 equa\u00e7\u00e3o fundamental da ondulat\u00f3ria\u00a0 —\u00a0 c=\u03bbv\u00a0 —\u00a0 v=\u03bb\/c (I)\u00a0 —\u00a0 equa\u00e7\u00e3o de Plank\u00a0 —\u00a0 E=hv (II)\u00a0 —\u00a0 relacionando (I) com (II)\u00a0 —\u00a0 E=hc\/\u03bb\u00a0 —\u00a0 raz\u00e3o pedida\u00a0 —\u00a0 R=E<\/b><\/span><\/span><\/span>vermelho<\/b><\/span><\/span><\/sub><\/span>\/E<\/b><\/span><\/span><\/span>verde<\/b><\/span><\/span><\/sub><\/span>=(hc\/\u03bb<\/b><\/span><\/span><\/span>vermelho<\/b><\/span><\/span><\/sub><\/span>)\/(hc\/\u03bb<\/b><\/span><\/span><\/span>verde<\/b><\/span><\/span><\/sub><\/span>)\u00a0 —\u00a0 R=E<\/b><\/span><\/span><\/span>vermelho<\/b><\/span><\/span><\/sub><\/span>\/E<\/b><\/span><\/span><\/span>verde<\/b><\/span><\/span><\/sub><\/span>=\u03bb<\/b><\/span><\/span><\/span>vermelho<\/b><\/span><\/span><\/sub><\/span>\/\u03bb<\/b><\/span><\/span><\/span>verde<\/b><\/span><\/span><\/sub><\/span>=650\/500\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R=1,3<\/b><\/span><\/span><\/span><\/p>\n

b) Dados\u00a0 — \u00a0h = 6,6<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/sub><\/span>10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>\u00a0J.s\u00a0 — \u00a0m = 5<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/sub><\/span>10<\/b><\/span><\/span><\/span>-26<\/b><\/span><\/span><\/sup><\/span>\u00a0kg\u00a0 —\u00a0 \u03bb = 660 nm = 6,6<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/sub><\/span>10<\/b><\/span><\/span><\/span>-7<\/b><\/span><\/span><\/sup><\/span>\u00a0m\u00a0 —\u00a0 a varia\u00e7\u00e3o da quantidade de movimento do \u00e1tomo \u00e9 igual \u00e0 quantidade de movimento do f\u00f3ton\u00a0 —\u00a0 \u2206Q<\/b><\/span><\/span><\/span>\u00e1tomo<\/b><\/span><\/span><\/sub><\/span>=p<\/b><\/span><\/span><\/span>f\u00f3ton<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 m.\u2206V<\/b><\/span><\/span><\/span>\u00e1tomo<\/b><\/span><\/span><\/sub><\/span>=h\/\u03bb\u00a0 —\u00a0 \u2206V<\/b><\/span><\/span><\/span>\u00e1tomo<\/b><\/span><\/span><\/sub><\/span>=h\/\u03bbm=6,6.10<\/b><\/span><\/span><\/span>-34<\/b><\/span><\/span><\/sup><\/span>\/6,6.10<\/b><\/span><\/span><\/span>-7<\/b><\/span><\/span><\/sup><\/span>x<\/b><\/span><\/span><\/span><\/p>\n

5.10<\/b><\/span><\/span><\/span>-26<\/b><\/span><\/span><\/sup><\/span>=0,92\u00a0 —\u00a0 \u2206V<\/b><\/span><\/span><\/span>\u00e1tomo<\/b><\/span><\/span><\/sub><\/span>=2,0.10<\/b><\/span><\/span><\/span>-2<\/b><\/span><\/span><\/sup><\/span>m\/s<\/b><\/span><\/span><\/span><\/p>\n

50-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>As duas leis estabelecidas por Phillip Lenard para o efeito fotoel\u00e9trico s\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

1\u00aa Lei: para determinada frequ\u00eancia, o n\u00famero de el\u00e9trons emitidos (conhecidos como fotoel\u00e9trons) pela placa iluminada (emissora)\u00a0<\/b><\/span><\/span><\/span>\u00e9 proporcional \u00e0 intensidade da luz<\/b><\/span><\/span><\/span><\/span>\u00a0nela incidente.<\/b><\/span><\/span><\/span><\/p>\n

2\u00aa Lei: a energia cin\u00e9tica dos fotoel\u00e9trons\u00a0<\/b><\/span><\/span><\/span>depende da frequ\u00eancia<\/b><\/span><\/span><\/span><\/span>\u00a0da radia\u00e7\u00e3o incidente na placa emissora, n\u00e3o dependendo da intensidade dessa radia\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

Como, na situa\u00e7\u00e3o\u00a0<\/b><\/span><\/span><\/span>b<\/b><\/span><\/span><\/span>, a intensidade da luz incidente na placa emissora \u00e9 o dobro em rela\u00e7\u00e3o \u00e0 situa\u00e7\u00e3o\u00a0<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/span>, de acordo com a 1\u00aa lei, o n\u00famero de el\u00e9trons liberados tamb\u00e9m \u00e9 o dobro, provocando corrente el\u00e9trica tamb\u00e9m duas vezes maior\u00a0 —\u00a0 i<\/b><\/span><\/span><\/span>b<\/b><\/span><\/span><\/sub><\/span>\u00a0= 2<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sub><\/span>i<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 como se trata da mesma radia\u00e7\u00e3o nas duas situa\u00e7\u00f5es (mesma frequ\u00eancia), a 2\u00aa lei garante que energia cin\u00e9tica dos fotoel\u00e9trons tamb\u00e9m \u00e9 a mesma, exigindo o mesmo potencial el\u00e9trico de frenamento (<\/b><\/span><\/span><\/span>-V<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>)<\/b><\/span><\/span><\/span>\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>R- C<\/b><\/span><\/span><\/span><\/p>\n

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

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

01-\u00a0<\/b><\/span><\/span><\/span>01.Correta\u00a0 — A figura abaixo mostra o gr\u00e1fico da energia cin\u00e9tica do el\u00e9tron extra\u00eddo em fun\u00e7\u00e3o da frequ\u00eancia da radia\u00e7\u00e3o (f\u00f3ton, cor) incidente, para uma mesma placa met\u00e1lica (c\u00e9lula fotoel\u00e9trica).<\/b><\/span><\/span><\/span><\/p>\n

f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0\u00e9 a freq\u00fc\u00eancia m\u00ednima (frequ\u00eancia de corte) necess\u00e1ria para produzir o efeito fotoel\u00e9trico. Se f=f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0o el\u00e9tron \u00e9 liberado, mas sua energia cin\u00e9tica \u00e9 nula. Para freq\u00fc\u00eancias inferiores a f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0o fen\u00f4meno n\u00e3o ocorre. Por\u00e9m, para valores superiores a f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>, o n\u00famero de el\u00e9trons arrancados \u00e9 diretamente proporcional \u00e0 intensidade da radia\u00e7\u00e3o eletromagn\u00e9tica incidente, ou seja, aumentando a intensidade da radia\u00e7\u00e3o (freq\u00fc\u00eancia, cor) incidente no metal, aumenta-se o n\u00edvel energ\u00e9tico dos f\u00f3tons incidentes, aumentando assim n\u00famero de el\u00e9trons arrancados.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

02. Correta\u00a0 —\u00a0 veja 01.<\/b><\/span><\/span><\/span><\/p>\n

04. Falsa\u00a0 — \u00e0 medida que a freq\u00fc\u00eancia (cor, n\u00edvel energ\u00e9tico) da radia\u00e7\u00e3o incidente aumenta, a energia cin\u00e9tica dos el\u00e9trons emitidos tamb\u00e9m aumenta. Mas, para a mesma freq\u00fc\u00eancia f (cor, n\u00edvel energ\u00e9tico) a energia cin\u00e9tica dos el\u00e9trons emitidos \u00e9 sempre a mesma.<\/b><\/span><\/span><\/span><\/p>\n

08. Correta\u00a0 —\u00a0 Foi Albert Einstein que explicou corretamente o efeito fotoel\u00e9trico em 1921, recebendo por isso o pr\u00eamio Nobel da F\u00edsica. Segundo Einstein a energia de qualquer radia\u00e7\u00e3o luminosa (inclusive luz) n\u00e3o se espalha uniforme e continuamente pelo espa\u00e7o mas, sim, concentrada em pequenos \u201cpacotes\u201dque carregam uma quantidade bem definida de energia. Cada um desses pacotes \u00e9 denominado\u00a0quantum\u00a0de energia e esse modelo constru\u00eddo por Einstein recebeu o nome de\u00a0teoria\u00a0 dos quanta.\u00a0Quanta, em latim \u00e9 plural de quantum, que significa \u201cquantidade\u201d.<\/b><\/span><\/span><\/span><\/p>\n

Esses\u00a0quanta\u00a0de energia radiante\u00a0foram denominados de f\u00f3tons.\u00a0<\/b><\/span><\/span><\/span><\/p>\n

16. Falsa\u00a0 —\u00a0 Essa\u00a0energia m\u00ednima para extrair um el\u00e9tron\u00a0da placa met\u00e1lica \u00e9 denominada\u00a0fun\u00e7\u00e3o trabalho\u00a0e est\u00e1 relacionada com o tipo de metal utilizado e depende da frequ\u00eancia da radia\u00e7\u00e3o incidente.<\/b><\/span><\/span><\/span><\/p>\n

Corretas:01,02 e 08\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0soma 11.<\/b><\/span><\/span><\/span><\/p>\n

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

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

A correta numera\u00e7\u00e3o dos par\u00eanteses, de cima para baixo, \u00e9<\/b><\/span><\/span><\/span><\/p>\n

A) 1 \u2013 2 \u2013 3 \u2013 4 \u2013 5\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

B) 2 \u2013 1 \u2013 4 \u2013 3 \u2013 5\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

C) 3 \u2013 2 \u2013 5 \u2013 4 \u2013 1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

D) 4 \u2013 3 \u2013 5 \u2013 2 \u2013 1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/b><\/span><\/span><\/span><\/p>\n

E) 5 \u2013 2 \u2013 1 \u2013 4 \u2013 3<\/b><\/span><\/span><\/span><\/p>\n

\u00a0A express\u00e3o E=h.f afirma que quanto maior a frequ\u00eancia maior \u00e9 a energia do f\u00f3ton\u00a0 —\u00a0 observe nas tabelas abaixo que a freq\u00fc\u00eancia e consequentemente o n\u00edvel de energia dos f\u00f3tons aumenta do vermelho para<\/b><\/span><\/span><\/span><\/p>\n

\"\"\"\"<\/p>\n

o violeta e das ondas de r\u00e1dio para os raios gama\u00a0 —\u00a0<\/b><\/span><\/span><\/span>\u00a0R- C<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

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

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

As duas leis estabelecidas por Phillip Lenard para o efeito fotoel\u00e9trico s\u00e3o:<\/b><\/span><\/span><\/span>\"\"<\/p>\n

1\u00aa Lei: para determinada frequ\u00eancia, o n\u00famero de el\u00e9trons emitidos (conhecidos como fotoel\u00e9trons) pela placa iluminada (emissora)\u00a0<\/b><\/span><\/span><\/span>\u00e9 proporcional \u00e0 intensidade da luz<\/b><\/span><\/span><\/span><\/span>\u00a0nela incidente.<\/b><\/span><\/span><\/span><\/p>\n

2\u00aa Lei: a energia cin\u00e9tica dos fotoel\u00e9trons\u00a0<\/b><\/span><\/span><\/span>depende da frequ\u00eancia<\/b><\/span><\/span><\/span><\/span>\u00a0da radia\u00e7\u00e3o incidente na placa emissora, n\u00e3o dependendo da intensidade dessa radia\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

Como, na situa\u00e7\u00e3o\u00a0<\/b><\/span><\/span><\/span>b<\/b><\/span><\/span><\/span>, a intensidade da luz incidente na placa emissora \u00e9 o dobro em rela\u00e7\u00e3o \u00e0 situa\u00e7\u00e3o\u00a0<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/span>, de acordo com a 1\u00aa lei, o n\u00famero de el\u00e9trons liberados tamb\u00e9m \u00e9 o dobro, provocando corrente el\u00e9trica tamb\u00e9m duas vezes maior\u00a0 —\u00a0 i<\/b><\/span><\/span><\/span>b<\/b><\/span><\/span><\/sub><\/span>\u00a0= 2<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sub><\/span>i<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 como se trata da mesma radia\u00e7\u00e3o nas duas situa\u00e7\u00f5es (mesma frequ\u00eancia), a 2\u00aa lei garante que energia cin\u00e9tica dos fotoel\u00e9trons tamb\u00e9m \u00e9 a mesma, exigindo o mesmo potencial el\u00e9trico de frenamento (<\/b><\/span><\/span><\/span>-V<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>)<\/b><\/span><\/span><\/span>\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>R- C<\/b><\/span><\/span><\/span><\/p>\n

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

A) A emiss\u00e3o de el\u00e9trons devido \u00e0 radia\u00e7\u00e3o incidente sobre o emissor surge quase que instantaneamente, independente se a radia\u00e7\u00e3o (luz) incidente tiver baixa intensidade\u00a0 —\u00a0 o atraso entre o tempo de incid\u00eancia da ilumina\u00e7\u00e3o e o tempo de emiss\u00e3o dos el\u00e9trons \u00e9 da ordem de 10<\/b><\/span><\/span><\/span>-9\u00a0<\/b><\/span><\/span><\/sup><\/span>s (praticamente instant\u00e2neo)\u00a0 —\u00a0 esse comportamento se justifica pelo modelo corpuscular da luz, proposto por Einstein\u00a0 — \u00a0a radia\u00e7\u00e3o \u00e9 formada por pequenos pacotes de energia (f\u00f3tons) que, ao colidirem diretamente com um dos el\u00e9trons da superf\u00edcie, transmite instantaneamente toda sua energia para o el\u00e9tron\u00a0 —\u00a0 ent\u00e3o, ele \u00e9 arrancando-o, imediatamente da superf\u00edcie.<\/b><\/span><\/span><\/span><\/p>\n

B) O efeito fotoel\u00e9trico s\u00f3 surge se o metal receber um feixe de radia\u00e7\u00e3o com energia superior \u00e0 energia m\u00ednima de remo\u00e7\u00e3o dos el\u00e9trons do metal, provocando a sua sa\u00edda das \u00f3rbitas o que pode ocorrer sem energia cin\u00e9tica (se a energia da radia\u00e7\u00e3o for igual \u00e0 energia de remo\u00e7\u00e3o) ou com energia cin\u00e9tica, se a energia da radia\u00e7\u00e3o exceder a energia de remo\u00e7\u00e3o dos el\u00e9trons.<\/b><\/span><\/span><\/span><\/p>\n

Essa\u00a0energia m\u00ednima para extrair um el\u00e9tron\u00a0da placa met\u00e1lica \u00e9 denominada\u00a0fun\u00e7\u00e3o trabalho\u00a0e est\u00e1 relacionada com o tipo de metal utilizado.\u00a0Se a energia do f\u00f3ton que incide (h.f) for maior que a fun\u00e7\u00e3o trabalho (W) a energia em excesso ser\u00e1 energia cin\u00e9tica (Ec), de modo que\u00a0 — \u00a0W=h.f \u2013 E<\/b><\/span><\/span><\/span>c<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 denominada\u00a0equa\u00e7\u00e3o fotoel\u00e9trica de Einstein..<\/b><\/span><\/span><\/span><\/p>\n

C) A figura abaixo mostra o gr\u00e1fico da energia cin\u00e9tica do el\u00e9tron extra\u00eddo em fun\u00e7\u00e3o da frequ\u00eancia da radia\u00e7\u00e3o (f\u00f3ton, cor) incidente, para uma mesma placa met\u00e1lica (c\u00e9lula fotoel\u00e9trica).<\/b><\/span><\/span><\/span>\"\"<\/p>\n

F<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0\u00e9 a freq\u00fc\u00eancia m\u00ednima (frequ\u00eancia de corte) necess\u00e1ria para produzir o efeito fotoel\u00e9trico. Se f=f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0o el\u00e9tron \u00e9 liberado, mas sua energia cin\u00e9tica \u00e9 nula. Para freq\u00fc\u00eancias inferiores a fo\u00a0o fen\u00f4meno n\u00e3o ocorre. Por\u00e9m, para valores superiores a f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>, o n\u00famero de el\u00e9trons arrancados \u00e9 diretamente proporcional \u00e0 intensidade da radia\u00e7\u00e3o eletromagn\u00e9tica incidente, ou seja, aumentando a intensidade da radia\u00e7\u00e3o (freq\u00fc\u00eancia, cor) incidente no metal, aumenta-se o n\u00edvel energ\u00e9tico dos f\u00f3tons incidentes, aumentando assim n\u00famero de el\u00e9trons arrancados.<\/b><\/span><\/span><\/span><\/p>\n

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

I. Correta\u00a0 — \u00a0\u00a0Quando a luz interage com a mat\u00e9ria atrav\u00e9s de absor\u00e7\u00e3o, emiss\u00e3o, choques, etc., ela se comporta como part\u00edcula (modelo corpuscular), mas para os fen\u00f4menos referentes \u00e0 sua propaga\u00e7\u00e3o, reflex\u00e3o, refra\u00e7\u00e3o, interfer\u00eancia, etc., ela se comporta como onda.<\/b><\/span><\/span><\/span><\/p>\n

II. Correta\u00a0 —\u00a0 A figura abaixo mostra o gr\u00e1fico da energia cin\u00e9tica do el\u00e9tron extra\u00eddo em fun\u00e7\u00e3o da frequ\u00eancia da radia\u00e7\u00e3o (f\u00f3ton, cor) incidente, para uma mesma placa met\u00e1lica (c\u00e9lula fotoel\u00e9trica).<\/b><\/span><\/span><\/span>\"\"<\/p>\n

F<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0\u00e9 a freq\u00fc\u00eancia m\u00ednima (frequ\u00eancia de corte) necess\u00e1ria para produzir o efeito fotoel\u00e9trico. Se f=f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0o el\u00e9tron \u00e9 liberado, mas sua energia cin\u00e9tica \u00e9 nula. Para freq\u00fc\u00eancias inferiores a f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0o fen\u00f4meno n\u00e3o ocorre. Por\u00e9m, para valores superiores a f<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>, o n\u00famero de el\u00e9trons arrancados \u00e9 diretamente proporcional \u00e0 intensidade da radia\u00e7\u00e3o eletromagn\u00e9tica incidente, ou seja, aumentando a intensidade da radia\u00e7\u00e3o (freq\u00fc\u00eancia, cor) incidente no metal, aumenta-se o n\u00edvel energ\u00e9tico dos f\u00f3tons incidentes, aumentando assim n\u00famero de el\u00e9trons arrancados.<\/b><\/span><\/span><\/span><\/p>\n

III. Falsa\u00a0 — \u00a0A emiss\u00e3o e a energia \u00a0dos el\u00e9trons arrancados dependem da freq\u00fc\u00eancia e n\u00e3o da intensidade da radia\u00e7\u00e3o eletromagn\u00e9tica incidente.<\/b><\/span><\/span><\/span><\/p>\n

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

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

\"\"<\/p>\n

As duas leis estabelecidas por Phillip Lenard para o efeito fotoel\u00e9trico s\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

1\u00aa Lei: para determinada frequ\u00eancia, o n\u00famero de el\u00e9trons emitidos (conhecidos como fotoel\u00e9trons) pela placa iluminada (emissora)\u00a0<\/b><\/span><\/span><\/span>\u00e9 proporcional \u00e0 intensidade da luz<\/b><\/span><\/span><\/span><\/span>\u00a0nela incidente.<\/b><\/span><\/span><\/span><\/p>\n

2\u00aa Lei: a energia cin\u00e9tica dos fotoel\u00e9trons\u00a0<\/b><\/span><\/span><\/span>depende da frequ\u00eancia<\/b><\/span><\/span><\/span><\/span>\u00a0da radia\u00e7\u00e3o incidente na placa emissora, n\u00e3o dependendo da intensidade dessa radia\u00e7\u00e3o.<\/b><\/span><\/span><\/span><\/p>\n

Como, na situa\u00e7\u00e3o\u00a0<\/b><\/span><\/span><\/span>b<\/b><\/span><\/span><\/span>, a intensidade da luz incidente na placa emissora \u00e9 o dobro em rela\u00e7\u00e3o \u00e0 situa\u00e7\u00e3o\u00a0<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/span>, de acordo com a 1\u00aa lei, o n\u00famero de el\u00e9trons liberados tamb\u00e9m \u00e9 o dobro, provocando corrente el\u00e9trica tamb\u00e9m duas vezes maior\u00a0 —\u00a0 i<\/b><\/span><\/span><\/span>b<\/b><\/span><\/span><\/sub><\/span>\u00a0= 2<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/sub><\/span>i<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sub><\/span>\u00a0 —\u00a0 como se trata da mesma radia\u00e7\u00e3o nas duas situa\u00e7\u00f5es (mesma frequ\u00eancia), a 2\u00aa lei garante que energia cin\u00e9tica dos fotoel\u00e9trons tamb\u00e9m \u00e9 a mesma, exigindo o mesmo potencial el\u00e9trico de frenamento (<\/b><\/span><\/span><\/span>-V<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>)<\/b><\/span><\/span><\/span>\u00a0 —\u00a0\u00a0<\/b><\/span><\/span><\/span>R- C<\/b><\/span><\/span><\/span><\/p>\n

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

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

\u00a0Resolu\u00e7\u00f5es comentadas dos exerc\u00edcios de vestibulares sobre Efeito Fotoel\u00e9trico 01- R- B\u00a0 —\u00a0 veja teoria 02- R- E\u00a0\u00a0—\u00a0 veja teoria 03-\u00a0a) Falsa\u00a0 —\u00a0 a massa de um el\u00e9tron vale aproximadamente m=9,11.10-28g. b) Correta\u00a0 —\u00a0 veja teoria c) Falsa\u00a0 —\u00a0 as massas dos pr\u00f3tons e dos n\u00eautrons s\u00e3o praticamente iguais. d) Falsa\u00a0 —\u00a0 existe a dualidade onda- part\u00edcula. R- B 04-\u00a0I-<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2478,"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-2482","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2482","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=2482"}],"version-history":[{"count":4,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2482\/revisions"}],"predecessor-version":[{"id":10718,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2482\/revisions\/10718"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2478"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2482"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}