{"id":5603,"date":"2020-11-09T03:14:58","date_gmt":"2020-11-09T03:14:58","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=5603"},"modified":"2024-06-26T14:14:59","modified_gmt":"2024-06-26T14:14:59","slug":"enem-2020-ondulatoria","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/enem\/enem-2020-ondulatoria\/","title":{"rendered":"ENEM – 2020 – ONDULAT\u00d3RIA"},"content":{"rendered":"

ONDULAT\u00d3RIA<\/span><\/span><\/span><\/p>\n

01-\u00a0<\/b><\/span><\/span><\/span>(ENEM-MEC-018)<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

<\/p>\n

<\/p>\n

<\/p>\n

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

02-\u00a0<\/b><\/span><\/span><\/span>(ENEM-MEC-018)<\/b><\/span><\/span><\/span><\/p>\n

<\/p>\n

<\/p>\n

<\/p>\n

<\/p>\n

 <\/p>\n

03-\u00a0<\/b><\/span><\/span><\/span>(ENEM-MEC-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

A\u00a0<\/b><\/span><\/span>figura mostra<\/b><\/span><\/span>\u00a0como \u00e9 a\u00a0<\/b><\/span><\/span>emiss\u00e3o de radia\u00e7\u00e3o eletromagn\u00e9tica\u00a0<\/b><\/span><\/span>para\u00a0<\/b><\/span><\/span>cinco tipos de l\u00e2mpada: haleto met\u00e1lico, tungst\u00eanio, merc\u00fario, x\u00eanon e LED (diodo emissor de luz).<\/b><\/span><\/span><\/span><\/span><\/p>\n

As\u00a0<\/b><\/span><\/span>\u00e1reas marcadas em cinza s\u00e3o proporcionais \u00e0 intensidade da energia liberada pela l\u00e2mpada.<\/b><\/span><\/span><\/span><\/span><\/p>\n

As\u00a0<\/b><\/span><\/span>linhas pontilhadas mostram a sensibilidade do olho humano aos diferentes comprimentos de onda. UV e IV\u00a0<\/b><\/span><\/span>s\u00e3o as\u00a0<\/b><\/span><\/span>regi\u00f5es do ultravioleta e do infravermelho,\u00a0<\/b><\/span><\/span>respectivamente.<\/b><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

Um\u00a0<\/b><\/span><\/span>arquiteto deseja iluminar uma sala usando uma l\u00e2mpada que produza boa ilumina\u00e7\u00e3o,\u00a0<\/b><\/span><\/span>mas\u00a0<\/b><\/span><\/span>que n\u00e3o aque\u00e7a o ambiente.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Qual tipo de l\u00e2mpada melhor atende ao desejo do arquiteto?<\/b><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

Para\u00a0<\/b><\/span><\/span>se obter boa ilumina\u00e7\u00e3o\u00a0<\/b><\/span><\/span>como\u00a0<\/b><\/span><\/span>deseja o arquiteto\u00a0<\/b><\/span><\/span>voc\u00ea deve procurar\u00a0<\/b><\/span><\/span>maior quantidade de intensidade emitida (\u00e1rea cinza)\u00a0<\/b><\/span><\/span>que que\u00a0<\/b><\/span><\/span>est\u00e3o dentro das linhas pontilhadas<\/b><\/span><\/span>, mais\u00a0<\/b><\/span><\/span>sens\u00edveis, percept\u00edveis ao\u00a0<\/b><\/span><\/span>olho humano,\u00a0<\/b><\/span><\/span>que \u00e9 o caso da LED.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Al\u00e9m disso, a\u00a0<\/b><\/span><\/span>LED fornece muito pouca intensidade na faixa do infravermelho (IF),\u00a0<\/b><\/span><\/span>que\u00a0<\/b><\/span><\/span>emite calor, n\u00e3o aquecendo o ambiente, conforme desejo do arquiteto. Por esse motivo as l\u00e2mpadas de tungst\u00eanio e x\u00eanon devem ser evitadas (ampla regi\u00e3o de infravermelho).<\/b><\/span><\/span><\/span><\/span><\/p>\n

Observe ainda que as\u00a0<\/b><\/span><\/span>l\u00e2mpadas de Merc\u00fario e de Haleto met\u00e1lico possuem regi\u00f5es na parte vis\u00edvel,<\/b><\/span><\/span>\u00a0mas\u00a0<\/b><\/span><\/span>n\u00e3o t\u00e3o amplas quanto \u00e0s da LED.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

 <\/p>\n

04-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span>(ENEM-MEC-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

Em uma\u00a0<\/b><\/span><\/span>linha de transmiss\u00e3o de informa\u00e7\u00f5es por fibra \u00f3ptica,<\/b><\/span><\/span>\u00a0quando um\u00a0<\/b><\/span><\/span>sinal diminui sua intensidade\u00a0<\/b><\/span><\/span>para\u00a0<\/b><\/span><\/span>valores inferiores a 10 dB,\u00a0<\/b><\/span><\/span>este\u00a0<\/b><\/span><\/span>precisa ser retransmitido.<\/b><\/span><\/span><\/span><\/span><\/p>\n

No entanto,\u00a0<\/b><\/span><\/span>intensidades superiores a 100 dB n\u00e3o podem ser transmitidas adequadamente.<\/b><\/span><\/span><\/span><\/span><\/p>\n

A\u00a0<\/b><\/span><\/span>figura apresenta como se d\u00e1 a perda de sinal (perda \u00f3ptica)\u00a0<\/b><\/span><\/span>para\u00a0<\/b><\/span><\/span>diferentes comprimentos de onda para certo tipo de fibra \u00f3ptica.<\/b><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

Qual \u00e9 a m\u00e1xima dist\u00e2ncia,\u00a0<\/b><\/span><\/span>em\u00a0<\/b><\/span><\/span>km,\u00a0<\/b><\/span><\/span>que um\u00a0<\/b><\/span><\/span>sinal pode ser enviado nessa fibra sem ser necess\u00e1ria uma retransmiss\u00e3o?<\/b><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

Quando um\u00a0<\/b><\/span><\/span>sinal diminui sua intensidade\u00a0<\/b><\/span><\/span>para\u00a0<\/b><\/span><\/span>valores inferiores a 10 dB,\u00a0<\/b><\/span><\/span>este\u00a0<\/b><\/span><\/span>precisa ser retransmitido.<\/b><\/span><\/span><\/span><\/span><\/p>\n

e\u00a0<\/b><\/span><\/span>intensidades superiores a 100 dB n\u00e3o podem ser transmitidas adequadamente<\/b><\/span><\/span>.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Assim, a faixa\u00a0<\/b><\/span><\/span>de intensidade sonora em que a\u00a0<\/b><\/span><\/span>linha pode operar,\u00a0<\/b><\/span><\/span>sem retransmiss\u00e3o,\u00a0<\/b><\/span><\/span>est\u00e1\u00a0<\/b><\/span><\/span>compreendida entre<\/b><\/span><\/span>\u00a0100 dB \u2013 10 dB\u00a0<\/b><\/span><\/span>= 90 dB.<\/b><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

05-\u00a0<\/b><\/span><\/span><\/span>(ENEM-MEC-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/h4>\n

<\/p>\n

A\u00a0<\/b><\/span><\/span>depila\u00e7\u00e3o a laser\u00a0<\/b><\/span><\/span>(popularmente conhecida como\u00a0<\/b><\/span><\/span>depila\u00e7\u00e3o a laser<\/b><\/span><\/span>) consiste na\u00a0<\/b><\/span><\/span>aplica\u00e7\u00e3o de uma fonte de luz para aquecer\u00a0<\/b><\/span><\/span>e\u00a0<\/b><\/span><\/span>causar<\/b><\/span><\/span>\u00a0uma\u00a0<\/b><\/span><\/span>les\u00e3o localizada\u00a0<\/b><\/span><\/span>e\u00a0<\/b><\/span><\/span>controlada\u00a0<\/b><\/span><\/span>nos\u00a0<\/b><\/span><\/span>fol\u00edculos capilares.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Para\u00a0<\/b><\/span><\/span>evitar que outros tecidos<\/b><\/span><\/span>\u00a0sejam\u00a0<\/b><\/span><\/span>danificados, selecionam-se comprimentos de onda\u00a0<\/b><\/span><\/span>que s\u00e3o\u00a0<\/b><\/span><\/span>absorvidos pela melanina presente nos pelos,\u00a0<\/b><\/span><\/span>mas que\u00a0<\/b><\/span><\/span>n\u00e3o afetam a oxi-hemoglobina do sangue\u00a0<\/b><\/span><\/span>e a\u00a0<\/b><\/span><\/span>\u00e1gua dos tecidos da regi\u00e3o\u00a0<\/b><\/span><\/span>em que o\u00a0<\/b><\/span><\/span>tratamento ser\u00e1 aplicado.<\/b><\/span><\/span><\/span><\/span><\/p>\n

A\u00a0<\/b><\/span><\/span>figura mostra\u00a0<\/b><\/span><\/span>como \u00e9 a\u00a0<\/b><\/span><\/span>absor\u00e7\u00e3o de diferentes comprimentos de onda\u00a0<\/b><\/span><\/span>pela\u00a0<\/b><\/span><\/span>melanina, oxi-hemoglobina e \u00e1gua.<\/b><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

Qual \u00e9 o comprimento de onda<\/b><\/span><\/span>, em\u00a0<\/b><\/span><\/span>nm, ideal para a epila\u00e7\u00e3o a laser?<\/b><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

Basta analisar o gr\u00e1fico e o enunciado:<\/b><\/span><\/span><\/span><\/span><\/p>\n

Pelo enunciado,\u00a0para\u00a0<\/b><\/span><\/span>evitar que outros tecidos<\/b><\/span><\/span>\u00a0sejam\u00a0<\/b><\/span><\/span>danificados,\u00a0selecionam-se comprimentos de<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>onda\u00a0<\/b><\/span><\/span>que s\u00e3o\u00a0<\/b><\/span><\/span>absorvidos pela melanina\u00a0<\/b><\/span><\/span>(entre 400 nm e 1100 nm)\u00a0<\/b><\/span><\/span>presente nos pelos,\u00a0<\/b><\/span><\/span>mas que\u00a0<\/b><\/span><\/span>n\u00e3o afetam a oxi-hemoglobina do sangue\u00a0<\/b><\/span><\/span>(nulo em 700 nm)\u00a0e a\u00a0<\/b><\/span><\/span>\u00e1gua\u00a0<\/b><\/span><\/span>(nula inferior a 900 nm)\u00a0<\/b><\/span><\/span>dos tecidos da regi\u00e3o\u00a0<\/b><\/span><\/span>em que o\u00a0<\/b><\/span><\/span>tratamento ser\u00e1 aplicado.\u00a0<\/b><\/span><\/span>Conclus\u00e3o,<\/b><\/span><\/span>\u00a0700 nm.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

 <\/p>\n

06-<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span>(ENEM-MEC-017)<\/b><\/span><\/span><\/span><\/span><\/span><\/h4>\n

<\/p>\n

O\u00a0<\/b><\/span><\/span>trombone de Quincke<\/b><\/span><\/span>\u00a0\u00e9 um\u00a0<\/b><\/span><\/span>dispositivo experimental\u00a0<\/b><\/span><\/span>utilizado para\u00a0<\/b><\/span><\/span>demostrar o fen\u00f4meno da interfer\u00eancia de ondas sonoras.<\/b><\/span><\/span><\/span><\/span><\/p>\n

<\/p>\n

Quando o\u00a0<\/b><\/span><\/span>trajeto ADC \u00e9 igual ao trajeto AEC (<\/b><\/span><\/span>mesma diferen\u00e7a de caminho)\u00a0<\/b><\/span><\/span>capta-se um som muito intenso na sa\u00edda\u00a0<\/b><\/span><\/span>o que indica que a\u00a0<\/b><\/span><\/span>interfer\u00eancia \u00e9 construtiva e a fonte emitiu ondas em dire\u00e7\u00f5es opostas mas em concord\u00e2ncia de fase.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Quando se\u00a0<\/b><\/span><\/span>aumentou gradativamente o trajeto ADC\u00a0<\/b><\/span><\/span>at\u00e9 que fique como\u00a0<\/b><\/span><\/span>mostrado na figura\u00a0<\/b><\/span><\/span>a\u00a0<\/b><\/span><\/span>intensidade do som na sa\u00edda fica praticamente nula e a\u00ed voc\u00ea tem a primeira interfer\u00eancia destrutiva.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Na\u00a0<\/b><\/span><\/span>situa\u00e7\u00e3o da figura fornecida<\/b><\/span><\/span>\u00a0observe que o\u00a0<\/b><\/span><\/span>trecho AD \u00e9 10 cm maior que o trecho AE\u00a0<\/b><\/span><\/span>e que o\u00a0<\/b><\/span><\/span>trecho DC \u00e9 10 cm maior que o trecho EC<\/b><\/span><\/span>, o que\u00a0<\/b><\/span><\/span>implica que o caminho que a onda percorre no trajeto ACD \u00e9 20 cm maior que o caminho que a onda percorre no trajeto AEC.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Isso\u00a0<\/b><\/span><\/span>significa que a diferen\u00e7a de caminho entre uma interfer\u00eancia construtiva e a destrutiva sucessiva \u00e9 de d2\u00a0\u2013 d1\u00a0= 20 cm = 0,2 m.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Como na\u00a0<\/b><\/span><\/span>sa\u00edda o som \u00e9 praticamente nulo, a\u00ed\u00a0<\/b><\/span><\/span>voc\u00ea\u00a0<\/b><\/span><\/span>tem interfer\u00eancia destrutiva, cuja teoria est\u00e1 a seguir:<\/b><\/span><\/span><\/span><\/span><\/p>\n

\"ONDULAT\u00d3RIA\"<\/p>\n

O\u00a0<\/b><\/span><\/span>primeiro m\u00ednimo corresponde a n = 0\u00a0<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>d2\u00a0\u2013 d1\u00a0= (2n +1).\u00a0<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>0,2 = (2.0 + 1).\u00a0\u00a00,2 = 1.\u00a0
\n<\/b><\/span><\/span>\u00a0= 0,4 m.<\/b><\/span><\/span><\/span><\/span><\/p>\n

Utilizando a\u00a0<\/b><\/span><\/span>equa\u00e7\u00e3o fundamental da ondulat\u00f3ria\u00a0<\/b><\/span><\/span>com a velocidade do som no interior do tubo\u00a0<\/b><\/span><\/span>V = 320 m\/s\u00a0\u00a0= 0,4 m\u00a0<\/b><\/span><\/span>\u00a0<\/b><\/span><\/span>V =\u00a0.f\u00a0<\/b><\/span><\/span>\u00a0320 = 0,4.f\u00a0\u00a0f =\u00a0\u00a0\u00a0<\/b><\/span><\/span>f = 800 Hz.<\/b><\/span><\/span><\/span><\/span><\/p>\n

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

 <\/p>\n

Clique aqui para ver sobre o tema!<\/a><\/p>\n

Confira as v\u00eddeo aulas!<\/a><\/p>\n

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

 <\/p>\n","protected":false},"excerpt":{"rendered":"

ONDULAT\u00d3RIA 01-\u00a0(ENEM-MEC-018) R- C 02-\u00a0(ENEM-MEC-018)   03-\u00a0(ENEM-MEC-017) A\u00a0figura mostra\u00a0como \u00e9 a\u00a0emiss\u00e3o de radia\u00e7\u00e3o eletromagn\u00e9tica\u00a0para\u00a0cinco tipos de l\u00e2mpada: haleto met\u00e1lico, tungst\u00eanio, merc\u00fario, x\u00eanon e LED (diodo emissor de luz). As\u00a0\u00e1reas marcadas em cinza s\u00e3o proporcionais \u00e0 intensidade da energia liberada pela l\u00e2mpada. As\u00a0linhas pontilhadas mostram a sensibilidade do olho humano aos diferentes comprimentos de onda. UV e IV\u00a0s\u00e3o as\u00a0regi\u00f5es do ultravioleta<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":3575,"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-5603","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/5603","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=5603"}],"version-history":[{"count":3,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/5603\/revisions"}],"predecessor-version":[{"id":9757,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/5603\/revisions\/9757"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/3575"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=5603"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}