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  • Hi, I'm Ross, and today I'm going to be showing you the secret to making things invisible.

  • So this is something which you can do at home.

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

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

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

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

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

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

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

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

  • This is known as refraction.

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

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

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

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

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

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

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

  • And you'll also need something called glycerol.

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

  • It's also known as 'glycerine'.

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

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

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

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

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

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

  • ... it vanishes!

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

  • meaning the light can pass straight through

  • without being refracted.

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

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

  • Another one...

  • And, another one...

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

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

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

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

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

  • For more science to try at home,

  • check out Sarah and David investigating the sciences of sweets.

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

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

  • click subscribe. Thanks for watching.

Hi, I'm Ross, and today I'm going to be showing you the secret to making things invisible.

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B1 beaker tube test tube refraction water invisibility

How to make something invisible | Do Try This At Home | At-Bristol Science Centre

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    Cheng-Hong Liu posted on 2015/02/20
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