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牛顿听了都要流泪物理学曾经300年世纪大争论

2019-11-10 00:26:03 | 来源: 生物技术

生活不能没有阳光的滋润,否则,一切美好的事物都将黯然失色。白天,阳光透过淡薄的云层,照耀着苍茫大地,给生命带来希望,给人们带来温暖。沐浴着阳光,我们在成长。 可是,每当夜幕降临,阳光似乎和我们玩起了捉迷藏,独留寒冷夜色静静的陪伴着我们。因此,光是让万物生长,花儿绽放的源泉;是 让积雪融化,候鸟归家的动力;是让希望重燃,温暖心灵的良药。

牛顿听了都要流泪物理学曾经300年世纪大争论

牛顿听了都要流泪物理学曾经300年世纪大争论

那么在物理学中,光又是什么呢?在物理学中,光是个最特殊的物质,但可以说探索光的本性也就等于探索物质的本性。纵观历史,整个物理学正是围绕着物质究竟是波还是粒子而展开的。 爱因斯坦曾经说过:。那么光到底是和水一样是一种波吗?还是光是由很多很小的粒子组成的?

关于光的粒子说,17世纪曾为牛顿等所提倡,这种学说认为光是由光源发出的粒子,它从光源沿直线行进至被照物。这种观点曾被普遍接受。

1801 年托马斯.杨向这个观点进行了挑战。他在百叶窗上开了一个小洞,然后用厚纸片盖住,再在纸片上戳一个很小的洞。让光线透过,并用一面镜子反射透过的光线。然后他用一个厚约1/30英寸的纸片把这束光从中间分成两束。结果看到了相交的光线和阴影。这说明两束光线可以像波一样相互干涉。这个试验为一个世纪后量子学说的创立起到了至关重要的作用。这也就是著名的杨氏双孔干涉,该实验证明了光和水一样,是具有波的性质的,而且也不符合粒子的行为。且实验被评为“物理最美实验”之一。所以这是不是就证明了光就是波呢?

牛顿听了都要流泪物理学曾经300年世纪大争论

然而,我们知道水波通过水来传播,声波通过空气来传播,那么光波传播的介质是什么呢?我们知道光可以在真空传播,那么光到底还需要介质吗?如果不需要介质,那它还是波吗?

看视频来听一听Aaron对这个问题的解释吧!

友情提示:建议小伙伴们横屏放大看视频,以便清晰阅读字幕哦!

小助理

友情提示:建议小伙伴们横屏放大看视频,以便清晰阅读字幕哦!

光除了视觉体验,还在生活的方方面面造福人类,我们会用不同的电磁波的性质来帮助生活,例如,红外线的热效应,我们利用红外线对物体进行烘干,用红外线遥感进行远距离探测。

X射线的穿透本领很大。广泛应用于医学诊断和治疗,对医学发展起着至关重要的推动作用。

尽管如此,人们对光的利用远没达到成熟,还有待未来的进一步开发和利用。

参考阅读:Thomas Young’s double-slit experiment (杨氏双孔干涉实验)

文字详解:

课程文字版详解在此!!错过 Aaron 老师的课程视频或者想要详细了解课堂内容的小伙伴们,千万不要错过哦!!

I’ve got a question for you. What is light? If you're standing out on the field you're surrounded by light. What are you surrounded by? You can feel it hitting your skin. You can feel the sun as it moves through the day and you know at night it's going to be dark you won't be able to see as well. But what's the sun doing? Is it creatingwaves 波浪? Is it shootingparticles 粒子? What's happening? This is an important question and in the mid-1800s physicists didn't really know but they knew a couple of things about it. They knew that light had afinite 有限的speed and they knew that light had aconstant 恒定的speed. That meant that as it was traveling it stayed the same speed and that its speed was ameasurable 可测量的number. It didn't just travelinstantaneously 瞬间地. This was a good firstclue线索. But if we're trying tofigure out 弄明白what it actually is this doesn't really answer everything. Let's think about this. If it's a wave let's think about other waves that we know.

Let's talk first about water because we know water has waves. We’ve seen it. We can kind ofvisualize 想象it and we know that if we see water passing a small opening like this when it hits thatbarrier 障碍 and it goes to the opening then it will kind of curve around it it'lldiffract 衍射. And then you get it traveling in all of these directions all at once. Okay that's pretty good. Let’s just kind of do a little quickthought experiment 思想实验. If we add a second opening here what happens? Well you're gonna get the same effect and you'll get theselayers 层forming or this curving around thebarrier 障碍. But at each of theseintersection points 交叉点 you're gonna haveinterference 干涉. Now sometimes it will be constructive sometimes it'll be destructive but if you measure it at a point further along what you'll see if you measure the height of the water is you'll get thisinterference pattern干涉图样forming were actually the highest peak would be at the center of the twoslits 狭缝. But this is a really good demonstration of waveproperties 性质. So why not try it with light? Why not use this as a test to see if light behaves as a particle or as a Wave? Because surely if it was a particle what would happen is it would pass through these and you just get collections of the light at two points. You wouldn't get aninterference pattern 干涉图样forming it’ll be simple. It’ll be as though you were shooting balls through these little openings. So physicists did this experiment. They tried it out. What did they see? So they sent a plain wave along like this and what happened was on aprojection screen 投影屏幕on the other side they actually saw the interference pattern. They saw the same thing that they would have seen with water but after using light. So that seems prettydefinitive 决定性的. Light behaves as a wave! Okay! problem solved right? Not quite!

You know a water wave is just waving through the water. You know that sound waves are just waving through the air. What's a light waving through? What is themedium 介质that's carrying the light? Let'srecall 回忆a couple of things that we said a while back. We said that light has afinite 有限的speed and that it has aconstant 恒定的speed. So that means that as light is traveling through space it travels at one speed and we know that earth moves around the Sun. So what if we could take onebeam of light 光束 andsplit 劈开it into two and send them on differenttrajectories 轨道? So we send them one along with atrajectory 轨道that follows the motion of the earth and one that’sperpendicular 垂直的to the motion of the earth so that it would beunaffected不受影响的by the Earth's motion. It wouldn't see any change in its path length as the earth moves along. Well if there was amedium介质that the light was waving through then you would have a change in the path length that the light sees. This would result in interference when yourecombine 重组the beams. So they tried this and this experiment showed nothing. It showed nointerference干涉when theyrecombined 重组thebeams 光束. That meant that the light wasn't being caught up in this in thisother以太 (曾被假想成为光的传播介质)that they called it. What does that mean? Does that mean that light can't be a wave if it's not waving through anything? Does that mean that light is a particle that just travels along with the samemomentum动量as the Earth?

I'll leave you with one final thought. Maybe you've seen it in a movie. They use a device called aGeiger counter 盖革计数器 (一种探测X射线强度的计数仪器). What aGeiger counter盖革计数器is is that it counts x-rays. X-rays are kind of like a high-energy light and so you know that when you shine an x-ray on aGeiger counter 盖革计数器 it's gonna click and it'll click for each x-ray that it counts. But this is an interestingconcept 概念. TheGeiger counter盖革计数器is clicking once for a wave. If it was clicking once for a wave how would that be? That means you're taking an entire wave front andcollapsing瓦解it down to just onedetection探测? Well that’s kind ofcurious奇怪的. So maybe then the light is actually a particle? Maybe it's both of these things? And that was the bigrevelation被揭露的真相that light wasn't just a wave or a particle. We said it was both. It was both at the same time and itexhibited 展示bothproperties 性质. And this was very important in understanding and developingquantum mechanics 量子力学. Well we’ll talk more about that next time!

Quiz:

1.Which experiment showed that light behaves as a Wave? Briefly describe this experiment.

2.What did the example of a Geiger counter demonstrate?

3.What medium does light travel on?

4.In conclusion is light a wave or a particle?

小助理

小伙伴们,课听完了,可是词汇都记住了吗?那就请大家再一起复习一下单词吧!

重点词语

barrier 障碍

beam 光束

clue线索

collapsing 瓦解

concept 概念

constant 恒定的

curious奇怪的

definitive 决定性的

detection 探测

finite 有限的

instantaneously 瞬间地

interference 干涉

layer 层

measurable 可测量的

medium介质

perpendicular 垂直的

property 性质

recall 回忆

recombine 重组

revelation 被揭露的真相

split 劈开

slit 狭缝

trajectory 轨道

unaffected 不受影响的

visualize 想象

wave 波浪

重点词组

a beam of light 光束

figure out 弄明白

projection screen 投影屏幕

thought experiment 思想实验

专业术语

diffract 衍射

ether 以太 (曾被假想成为光的传播介质)

exhibit 展示

Geiger counter盖革计数器 (一种探测X射线强度的计数仪器)

interference pattern干涉图样

intersection points 交叉点

momentum 动量

particle 粒子

quantum mechanics 量子力学

纠音小课堂

Aaron老师的发音是不是特别好听!那么,纠音小课堂来啦!听听单词,句子该怎么读,保证让大家拥有一口流利的美式英语!!

我们今天的金句为:

It was a big revelation that light wasn't just a wave or a particle. It was both at the same time.

想要发好音请注意以下要点哦!

It was a big revelation­∧thatlight­wasn'tjust a wave∧or a particle.〡It wasboth­∧at thesametime.

连读:was a just a

失去爆破:it was big revelation that light light wasn’t wasn’t just at the

重读:见黄色高亮

语调:见箭头标注()

断句:短暂停顿见∧,稍长停顿见〡

易错单词:revelation particle

小助理

看不懂没关系,请听下面的录音,会有详细讲解哦!

温馨提示:

诵读示范:

慢速版诵读示范:第30秒

快速版诵读示范:第45秒

连读:第52秒

失去爆破:第1分22秒

易错单词:

revelation:第4分25秒

particle:第5分15秒

光的二象性还应用在生活哪些方面?欢迎大家在文章下方留言告诉我们哦~

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