Always asked myself this…
Physician friend explained that to me but i dont get it, thats why ELI5…
In: 333
So, the real question here is “why is glass so special that it gets to be transparent”
And to answer that question, we have to understand how light interacts with atoms. Light can only interact with atoms in two ways. It can be totally absorbed by the atom (typically by exciting an electron) or it can be partially absorbs and then release colored light of the energy level that the atom does not need.
So basically, light can only interact with atoms if the atoms’ electrons are able to be excited and absorb the light energy. If an atom cannot absorb any energy, then the light cannot interact with it and just pass through it.
So, what makes glass so special? It’s crystalline structure. Glass’ crystal structure is VERY stable, damn near every single atom is used up in a covalent bins and cannot absorb more energy. Which as we know means those atoms cannot interact with light. So the light just passes straight in through.
This also explains why the more perfect the glass, the clearer it is, but the more imperfections in the glass, the more it will gradually absorb/obscure light.
An objects transparency isn’t necessarily determined by it’s thickness. Transparency DOES tend to decrease as things get thicker but there way more important details to consider first.
Whether or not something allows light through it is dependent on its molecular structure. Molecules of different shapes, sizes, energies, and other properties will make some light get absorbed, some reflected, and some not react at all.
The cool part is this extends beyond visible light to other electromagnetic radiation such as radio waves, x-rays, gamma rays, and everything in between. You for example are opaque to most visible light (though you can see a flash light through the thin parts of your skin) but you are almost completely transparent to x-rays! What’s the exception? Your bones which is why they show up on the film and nothing else.
On the other end of the spectrum, infrared light is lower energy can come from distant stars and galaxies. When we try to observe them with normal telescopes, that visible light can be blocked by space dust. The brand new James Webb Space Telescope is specifically designed to look through that dust at the infrared instead.
This is because light can travel through glass, but it can’t through foil.
If light can’t get through something, you can’t see through it.
Metal has free states that electrons can be excited to, so when light comes in, it excites electrons and the light is not passed through.
Insulators (e.g. glass) have a very large energy requirement for the electrons to be excited, so generally light won’t have enough energy to excite the electrons, and the light passes through freely.
Not quite ELI5, but I think you’ll like this explanation.
To be transparent, light has to be able to pass through an object.
In glass, the molecules are lined up in such a way that light can go through them. In tin foil, the atoms are arranged in a way that makes some light bounce off them; the rest of the light gets caught by the atoms, resulting in the foil’s silvery colour.
What makes anything transparent is that light is able to pass through it without being scattered or blocked. Some materials, like metals are structured in such a way that they completely block the light, so you can’t see through it. Other materials, like many glasses, are structured so that the light passes through without being blocked or too distorted.
To a degree, thickness does affect whether you can see through an object. Even things like glasses have an upper limit to how thick they can be. Also, if you get thin enough, some opaque materials will become see-through, but those are at very small scales.
Found something online that may provide a [satisfactory answer](https://www.scientificamerican.com/article/what-determines-whether-a/).
because glass is clear where as tinfoil isnt, im seeing a lot of people not explaining like your 5
Wow there are so many incorrect answers and not very ELI5 answers here…
Firstly, when light enters glass (or any object), it interacts with a LOT of the atoms and even kinda “bounces around”. This is a gross oversimplification that relativity explains a bit more, but this is why light “slows down” when it enters glass. It doesn’t have to do with its atomic structure or shape.
We can observe this slowing down effect with Pink Floyd’s famous cover art. The light with more energy will be slowed down a little less than the light with less energy, and you’ll see white light break up into all of its components.
But why does the light pass through? Well in some materials, the atoms don’t have much need to capture that photon (light particle), and it’ll just bounce away. Glass happens to be one of those materials. There are other materials that really DO want to capture that photon, and usually store it in the form of heat.
If you put a metal cup and glass cup out in the sun, one of them will get really hot. Even a wooden one will get hotter than a glass one.
Glass is transparent and tin foil is opaque. Light passes through transparent things but bounces off opaque things
So, if you’re looking though 3m glass, light will bounce off objects on the other side, pass though the glass, and enter your eyes, thus you see the objects on the other side as light bounces off them and goes into your eyes
If you’re looking at tinfoil, light will bounce off objects on the other side, but then bounce back off the tinfoil and never reach your eyes. Light from the other side (Where you’re standing) will bounce off the tinfoil and enter your eyes, hence you will see the tin foil, but not what’s behind it
You can only see light that is able to reach your eyes
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