Scientists cant yet make an invisibility cloak1 like the one that Harry Potter2 uses.But,for the first time,theyve constructed a simple cloaking device that makes itself and somethingplaced inside it invisible to microwaves. Invisibility isnt possible yet with waves of light that the human eye can see.But it is nowpossible with microwaves.Like visible light,microwaves are a form of radiant energy.Theyare 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 thanthose of radio waves but longer than those of visible light. To a detector set up to receive microwaves on the other side of the ring,it looks as if thewaves never changed their paths as if there were no object in the way! So,the ring is effectively invisible. 练习: Acan now make an invisible cloak of the same kind as he uses. Ctry to invent a device Similar in idea to the invisible cloak he uses.
人教版高中英语选修9 Unit 2《Sailing the oceans》word单元测试1
人教版高中英语选修七Unit 3《Under the sea》(Reading Tasks)word同步讲练
人教版高中英语选修9 Unit 2《Sailing the oceans》word单元练习
人教版高中英语选修七Unit 4《Sharing》单元测试打包下载(3套)
人教版高中英语选修七Unit 4《Sharing》(Reading Tasks)word同步讲练
人教版高中英语选修9 Unit 4《Exploring plants》word单元测试2
人教版高中英语选修8 Unit 3《Inventors and inventions》word单元测试3
人教版高中英语选修9 Unit 4《Reading 》word单元练习
人教版高中英语选修8 Unit 2《Cloning》word单元测试3
人教版高中英语选修七Unit 4《Sharing》(Sentence Explanation)word同步讲练
人教版高中英语选修9 Unit 3《Australia》word单元测试2
人教版高中英语选修9 Unit 1《Breaking records》word单元测试
人教版高中英语选修七Unit 4《sharing》word精华练习及答案
人教版高中英语选修七Unit 2《Robots》(Words ^ Expressions)word同步讲练
人教版高中英语选修9 Unit 3《Australia》word单元测试1
人教版高中英语选修9 Unit 5《Inside advertising》word单元测试2
人教版高中英语选修七Unit 3《Under the sea》(Sentence Explanation)word同步讲练
人教版高中英语选修8 Unit 1《A land of diversity》word单元测试3
人教版高中英语选修七Unit 3《Under the sea》单元测试打包下载(3套)
人教版高中英语选修8 Unit 5《Meeting your ancestors》word单元测试3
人教版高中英语选修9 Unit 3《Australia》word专项训练1
人教版高中英语选修10 Unit 1《Nothing》word单元测试1
人教版高中英语选修七Unit 5《travelling abroad》word精华练习及答案
人教版高中英语选修8 Unit 4《Pygmalion》word单元测试3
人教版高中英语选修8 Unit 2《Cloning》word单元测试1
人教版高中英语选修9 Unit 4《Exploring plants》word单元测试1
人教版高中英语选修七Unit 3《Under the sea》(Grammar)word同步讲练
人教版高中英语选修七Unit 5《Travelling abroad》单元测试打包下载(3套)
人教版高中英语选修七Unit 4《Sharing》(Grammar)word同步讲练
人教版高中英语选修8 Unit 5《Meeting your ancestors》word单元测试2
| 不限 |
| 英语教案 |
| 英语课件 |
| 英语试题 |
| 不限 |
| 不限 |
| 上册 |
| 下册 |
| 不限 |