Translucent, yet hermetical !?

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Offline InCharacter

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Translucent, yet hermetical !?
« on: 24/11/2008 03:31:42 »
Say, this question has been asked many times, but I can't recall the exact answer: Why is it that in some scenarios, such as glass, matter can be translucent, and allow light to penetrate it, simultaneously holding back just about everything else, e.g., water, air, etc. ?



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Translucent, yet hermetical !?
« Reply #1 on: 24/11/2008 15:36:47 »
Basically, your question involves two different issues- the bonds between the atoms (which affect the mechanical properties) and  the way that em interacts the atoms (which can cause absorption of energy from em waves). Most substances interact with em waves and, for a dense material, which will be a strong solid, the absorption will be more. Glass, some plastics and ice are exceptions because they happen not to absorb em waves (much) at optical frequencies - but they are not very dense as solids go. They are, however, opaque to some wavelengths.

For a material to be transparent, the atoms must allow the light to 'go round' without taking a significant amount of its energy away. You can look at the phenomenon in terms of resonance; if the light doesn't resonate with the atoms, then it will (almost) ignore them.