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第111期:光速在玻璃中会变慢

来源:可可英语 编辑:Melody   VIP免费外教试听课 |  可可官方微信:ikekenet

We all know that light bends when it travels through glass, water, or other transparent material

我们知道光通过玻璃,水,或其他透明介质时会发生折射

that's how a microscope, lighthouse and spectacles work!

这也就是显微镜,灯塔和眼镜的工作原理

And you might even know that light bends

你可能还知道折射是因为

because it travels slower through glass or water than through air

玻璃中的光速比真空中要慢

but why does light slow down?

但光速为什么会慢下来

And how does it speed up again when it comes out on the other side?

而为什么光速又会在通过介质后恢复

There's nothing there to give it a push!

没有东西给光加速啊

Well, if you think light is a wave, it's easy to explain

如果把光看作波 这个问题很好解决

electromagnetic waves simply travel slower through glass than through air.

电磁波在玻璃中的速度比在空气中慢

So the wave crests are closer to each other,

所以波峰会更密集

but the light still oscillates the same number of times per second, it stays the same color.

但光的频率依然不变 也就是它的颜色不变

When the wave hits the air again, its color stays the same,

当光通过介质后 光的颜色依旧不变

while its crests spread out and it returns to light speed.

这时波峰会舒展开 光恢复到原来的速度

The simplified explanation is that the energy of a wave is determined by its frequency, or color, which doesn't change!

更简单的说法是 光的能量是由频率 也就是颜色决定 前后是不会改变的

So it doesn't need a boost to speed up at the other side.

所以它不需要额外的能量加速

images.jpg

But wait, you say!

等等

I thought light traveled at the same speed in every reference frame

我说过光速在任何参考系下不变

you still haven't explained how it can slow down!

但我始终没有说光速为什么会变慢

Well, now let's think about light as a particle.

这次我们把光看成粒子

When light goes through glass, it gets knocked around and bumps into all sorts of molecules and electrons.

当它穿过玻璃时 会撞上分子 电子等各种粒子

So whenever it's traveling, it's traveling at the speed of light

所以光子虽然一直以光速前进

but it's busy interacting with and scattering off lots of stuff along the way,

却在跟各种其他粒子撞来撞去

and it doesn't necessarily take the shortest path through the glass.

从而增加了行径的路程

It's like the President of the United States trying to cross a room

就像是奥观海同志穿过一间屋子

if the room is empty, he can walk across directly.

如果房间是空的 他可以直接通过

But if the room is full of people all of whom want to shake the President's hand,

但如果房间里都是想和他握手的人

even though he walks from person to person at full “Presidential-speed”,

就算他行走的速度保持不变

he'll get slowed down along the way.

也会在中途耽误时间

As soon as he reaches the far side of the room, though, he's free to resume his pace.

直到他挤出这间屋子 才能恢复到原来的速度

Full speed ahead, Mr. President!

全速前进 观海同志

重点单词   查看全部解释    
frame [freim]

想一想再看

n. 框,结构,骨架
v. 构成,把 ...

 
microscope ['maikrəskəup]

想一想再看

n. 显微镜

联想记忆
transparent [træns'perənt]

想一想再看

adj. 透明的,明显的,清晰的

联想记忆
boost [bu:st]

想一想再看

vt. 推进,提高,增加
n. 推进,增加

联想记忆
explanation [.eksplə'neiʃən]

想一想再看

n. 解释,说明

 
reference ['refrəns]

想一想再看

n. 参考,出处,参照
n. 推荐人,推荐函<

联想记忆
spread [spred]

想一想再看

v. 伸展,展开,传播,散布,铺开,涂撒
n.

 
haven ['heivn]

想一想再看

n. 港口,避难所,安息所 v. 安置 ... 于港中,

联想记忆
resume [ri'zju:m]

想一想再看

v. 再继续,重新开始
n. 简历,履历; 摘

联想记忆
frequency ['fri:kwənsi]

想一想再看

n. 频繁,频率

 


关键字: 英语视频 玻璃 光速

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