Why is glass transparent?



Why is glass transparent?

In: Physics

Glass is made up of many separate molecules, like sand. It isn’t until you add heat to all the different molecules at once.. then get them all hot enough, they melt together into glass.

Think of it like melting a bowl of m&ms in the microwave. Once the insides get hot enough, the chocolate oozes out and melts the shells.. that is the same as how glass is made.

The main reason is because glass’ core ingredient is normally Quartz, a clear stone found in sand that gains some wonky properties when heated. As all the ingredients of glass are combined and melted, the bonds between molecules break up and are unable to re-from into a crystal-like fashion. The way these molecules re-form do so in a way that *allows light to pass between them*, instead of getting bounced around scattered, resulting a transparent product. (Quartz itself can range from clear to white/clouded depending on how the molecules inside are arranged.)

(This is why a prism can cask a rainbow. The molecules are formed in a way that scatters/catches the light (photons) *just right.*)

[Here’s a video](https://ed.ted.com/lessons/why-is-glass-transparent-mark-miodownik) that does a great job of explaining the above with visuals!

Light is made of waves, specifically electromagnetic waves. Any solid material is going to be made of atoms, which are made up of electrically charged particles (protons and electrons). This means that both light and atoms can interact with each other through the electromagnetic field.

The strength of this interaction determines whether light can pass through an object or get absorbed by it.

At it’s core it’s about the wiggling of the light waves and the wiggling of the atoms in the material. They don’t wiggle together at the same speed and the light can’t be absorbed, much like if you try to push a person on the swing but don’t time it right you might just get knocked over. Light hitting a brick is more like pushing a swing in time with the swing. The energy from your arms is absorbed because your pushes are timed well. Light hitting a brick wiggles together with the atoms in the brick well and its energy gets absorbed.