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General Science / Why are substances Transparent ?
« on: 31/05/2019 08:34:11 »
To elaborate on what ukmicky said. Materials with "radom" or amorphous structure don’t have lots of internal faults. Where as crystalline materials commonly have lots of internal faults and facets that scatter and refract the light. It is not so much to do with how closely packed the atoms are. As qsmollin said everything is dependent on how the material interacts with photons of light as they try to pass through. Shorter wavelengths of light are more penetrating and have higher energy... so even a certain amount of lead which is very dense is transparent to gamma rays. And essentially with quantum mechanics everything has a certain amount of translucency by probability that a photon will make it through without interacting in any way. The density of the material just means there are more electrons in the way to increase the chance that a photon is going to interact with any field of charge present. Certain materials like metals will always be opaque to most light because they have a cloud of free electrons which are far more ready to interact with any light that comes along, electrons that are tightly bound to there atoms aren’t moving around causing a changing electric field. Thinking on a broader scale, a lightyear of lead is transparent to neutrinos since they hardly ever interact with anything, and that’s just your average one, some if they have enough energy could penetrate a thousand lightyears.