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 in a great trick
to show your friends
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 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.