Scientists can’t yet make an invisibility cloak1 like the one that Harry Potter2 uses. But, for the first time, they’ve constructed a simple cloaking device that makes itself and something placed inside it invisible to microwaves.
When a person “sees” an object, his or her eye senses many different waves of visible light as they bounce off the object. The eye and brain then work together to organize these sensations and reconstruct the object’s original shape. So, to make an object invisible, scientists have to keep waves from bouncing off it. And they have to make sure the object casts no shadow. Otherwise, the absence of reflected light on one side would give the object away.
Invisibility isn’t possible yet with waves of light that the human eye can see. But it is now possible with microwaves. like visible light，microwaves are a form of radiant energy. They are part of the electromagnetic spectrum, which also includes radio waves, infrared light, ultraviolet rays, X rays and gamma rays. The wavelengths of microwaves are shorter than those of radio waves but longer than those of visible light.
The scientist’s new “visibility device” is the size of a drink coaster and shaped like a ring. The ring is made of a special material with unusual ability. When microwaves strike the ring, very few bounce off it. Instead, they pass through the ring, which bends the waves all the way around until they reach the opposite side. The waves then return to their original paths.
To a detector set up to receive microwaves on the other side of the ring, it looks as if the waves never changed their paths - as if there were no object in the way! So，the ring is effectively invisible. When the researchers put a small copper loop inside the ring it，too，is nearly invisible. However，the cloaking device and anything inside it do casts a pale shadow. And the device works only for microwaves, not for visible light or any kind of electromagnetic radiation. So Harry Potter’s invisibility cloak doesn’t have any real competition yet.
練習(xí):
1. Harry Potter is mentioned in the passage，because scientists
A can now make an invisible cloak of the same kind as he uses.
B try to make an invisible cloak of the same kind as he uses.
C try to invent a device similar in idea to the invisible cloak he uses.
D know that it is possible to make an invisible cloak of the same kind.
2. What is true of microwaves?
A Their wavelengths are shorter than those of visible light.
B Their wavelengths arc longer than those of visible light.
C They are different from visible light as they are a kind of radiant energy.
D They are visible to the human eye.
3. What is NOT true of the invisibility device?
A It is made of a special material with unusual ability.
B Microwaves bounce off it when they strike it. www.Examw.com
C Microwaves pass through it when they strike it.
D It bends the microwaves all the way around until they reach the opposite side.
4. What does the word “coaster” mean in the passage?
A A disk or plate placed under a drinking glass to protect a table top.
B A vessel engaged in coastal trade.
C A roller coaster.
D A resident of a coastal area.
5. Harry Potter's invisibility cloak doesn't have any real competition yet, because
A scientists have not found out how his cloak works.
B the cloaking device is a total failure.
C the cloaking device works only for microwaves.
D the cloaking device works only for visible light.
答案與題解： 來自www.Examw.com
1. C 文章的第一段告訴我們，科學(xué)家還沒有發(fā)明哈里 ·波特使用的那種隱身衣，所以不能選 A;該段還告訴我們 ,科學(xué)家已制造了一種裝置，這種裝置能使自身或置于其中的物體不被微波發(fā)現(xiàn)，所以 C是正確選擇。也就是說，科學(xué)家發(fā)明的隱形裝置和哈里波特的隱身衣僅僅在概念上相同，這同時(shí)說明 B和D是錯(cuò)誤的選擇。
2. B 第三段昀后一句中告訴我們， A是錯(cuò)誤選擇， B是正確選擇。該段第三句說，微波與可見光一樣都是一種輻射能，所以 C的說法是錯(cuò)誤的，不能選擇；根據(jù)該段第一句 : with waves of light taht the human eye can see和第三句: Like visible light 可以得知 D是錯(cuò)誤的說法，也不能選擇。
3. B 第四段第三句說，當(dāng)微波到裝置表面， very few bounce off it。very few是幾乎沒有的意思，所以選擇 B。其他選擇所述內(nèi)容都可以很容易在該段中找到。
4. A 第四段第一句告訴我們，科學(xué)家的這個(gè)隱形裝置和一個(gè)杯墊差不多大小，所以 A是正確選擇。 Coaster是一個(gè)多義詞，其他幾個(gè)選擇是該詞的其他意思。 B:從事沿海貿(mào)易的船； C：過山車，摩天輪； D:海岸地區(qū)居民。
5. C A句在短文中沒有提到；按文章的內(nèi)容 B不是正確的說法；文章昀后一段說， And the device works only for microwaves，not for visible light，所以，C是正確選擇。