So this is something which you can do at home.

這件事在家就可以做

It's really easy and a great trick to show your friends.

它非常簡單，拿來耍朋友也很棒

But I assure you, it's not magic, it's all science.

但我向你保證，這不是魔法，而是科學

If you place a test tube into a beaker of water, you can still see the test tube,

如果你在裝水的燒杯裡放入一根試管，你還是看得到試管

despite the air, the water, and the tube all being transparent.

即使空氣、水還有試管都是透明的

This is because as the light passes from one material to another,

這是因為，當光穿越某種物質進入到另一種物質時

it changes speed and direction, allowing you to see the edges of the tube.

光的速度和方向會改變，讓你看得到試管的輪廓

But if the angle of the light changes, objects can appear distorted.

但如果光線的角度改變，東西看起來就會扭曲

Watch what happens to this picture on the other side the glass as we add water to it.

來看看我們把水加進玻璃杯時，玻璃另一側的圖片會怎樣

This is known as refraction.

這個現象稱為「折射」

As the lens of your eye changes shape, it allows you to focus on objects at different distances as it refracts the light.

隨著眼睛的水晶體改變形狀，光線被折射時可以讓你聚焦在遠近不同的物體上

Understanding this concept has led to the invention of lenses in glasses, cameras, and telescopes.

了解這個原理後，人發明了用在眼鏡、相機以及望遠鏡的透鏡

But what if we change the water for something else? Different materials have different refractive properties,

但如果我們把水換成別的東西呢？不同的物質有不同的折射特性

so if we switch the water for something which has the same refractive index as the glass,

所以，如果我們把水換成某種折射率和玻璃一樣的物質

the light will appear to pass straight through without changing speed or direction.

光線就會直直穿透，不會改變速度和方向

For your invisibility trick you'll need some Pyrex glass,

玩這個消失把戲會需要耐熱玻璃

so any measuring cyclinders or coffee pots which are made of Pyrex will be great for this.

因此任何用耐熱玻璃做的量筒或是咖啡壺都很適合

And you'll also need something called glycerol.

你還會需要一種叫作「甘油」（丙三醇）的東西

So, glycerol is a sweetener that you can get from the local chemist,

甘油是一種增甜劑，在地方藥房就弄得到

It's also known as 'glycerine'.

甘油 (glycerol) 也被稱為 glycerine

I'm going to be wearing some gloves for this because it can get pretty sticky.

我要戴上手套，因為甘油還滿黏的

You don't have to use glycerol though...

不過你也不一定要用甘油...

If you can't find any glycerol, then don't worry - baby oil, or vegetable oil will work just as well.

如果你找不到甘油，不用擔心，嬰兒油或是蔬菜油也都可以用

Here I have a beaker full of glycerol, and if I take a Pyrex test tube,

現在我有一個裝滿甘油的燒杯，如果我拿一支耐熱試管

and place it in to the beaker - we can still see it

放進燒杯裡，我們還是看得到試管

because of the air in the tube. But if I dip it just beneath the surface...

因為試管裡有空氣。但如果我把試管放到液面下方一點點...

... it vanishes!

試管就消失了！

So the pyrex and the glycerol have the same the refractive index,

耐熱玻璃和甘油的折射率一樣

meaning the light can pass straight through

意思是光線可以直直穿過

without being refracted.

不會被折射

This is a bit awkward - I've just dropped it in. Um... hold on let me see if I can get it back out.

呃這下尷尬了，試管掉進去了。恩...等等，我看看能不能拿出來

There we go. I'll pull that out of there. Hold on there's something else in here as well.

好啦，拿出來了。等等，裡面還有別的東西

Another one...

另一支...

And, another one...

還有另一支...

Hang on. There's something else... If I can just grab it and...

等等，還有東西...要是我能抓住它然後...

So there we go, this beaker has been hidden inside this big jar of glycerol the entire time!

拿出來了，這個燒杯一直都藏在這一大杯甘油裡！

Did you manage to spot it? Let us know if you did.

你有發現它嗎？如果有的話請告訴我們

So there we have it, the science of light and refraction, give it a go at home

就是這樣，光和折射的科學，在家試試吧

and tweet us to let us know if manage to fool any of your friends with this invisibility trick.

如果你用這個消失把戲成功騙倒了你的朋友，也可以在推特告訴我們

For more science to try at home,

想知道更多居家實驗

check out Sarah and David investigating the sciences of sweets.

可以看Sarah和David探究甜食中的科學

Or, if you'd like to see more about how your eyes work,

或者，如果你想知道我們的眼睛如何運作

why not watch an eyeball dissection? And for more science every week

何不看看眼睛解剖？想要每週有更多科學知識

click subscribe. Thanks for watching.

請點擊訂閱。謝謝觀賞。