So You Think You Know Glass?

Why is glass transparent of all objects?
Why is glass used in a mirror, instead of any other object?
Why haven’t these questions struck me before?

Well the third question I can’t answer, but the other two I will.

First of all, is glass a solid or liquid? Our textbooks will tell us that it’s a liquid, because we can see old glass panes thicker at the bottom than at the top. This is in fact wrong. This paper will tell you how poor our sense of “states of matter” is. To put that in perspective, it’s as poor as the decision making power is with M.U.N. debaters.

How is glass made? Our saviour Ted Ed will answer that for you.

The next question that comes up is how on earth is it transparent?

The above Ted Ed video might have given you some idea about it, but that’s not everything about it. To understand why glass is transparent let’s first understand why other things are not. We know that, it’s because those objects absorb all the colours except the one they are, but reflect that colour itself. Note: They reflect it. So obviously the next question is, why doesn’t glass reflect light and instead, lets it pass through?

Professor Moriarty will put some more perspective about this in our heads.

Let’s focus on the last part of that video where he shows us a semiconductor. The semiconductor is actually doing three things at a time. It is reflecting an orange tint, so its molecules are throwing back orange light at you. It is translucent, so not all light is being reflected. And it is absorbing light as well, that we know via the experiment. So the question actually changes to why do objects reflect light at all? To think about that let’s look at the worlds best reflector: Mirror.

Mirror mirror on the wall, why do you use glass of all?

Well glass is awfully straight, and it remains that way throughout its life (unlike Kevin Spacey). No other transparent substance is known to remain in such great shape. To put all this in perspective, here’s how mirrors are actually made.

Now that that’s done let’s focus on our first burning question about its transparency. Every object reflects light, even glass does, that’s how mirrors have a colour! What? Mirrors have a colour? Yes! – Hey Vsauce, Michael here.

Yes that’s also why you see your own reflection while talking to a friend who wears spectacles. Everything reflects some amount of light. Glass does everything spectacularly, it reflects, it absorbs, and it transmits. So that’s cleared then, glass is just an object that does all of the three things. The question is, why do other solids not allow light to pass through them at all?

Find the answer in our article about transparency.

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