Mirrors in quantum mechanics

by superg33k
Tags: mechanics, mirrors, quantum
superg33k is offline
Jun7-11, 03:54 AM
P: 96
How do mirrors work in quantum mechanics? Does light get absorbed by the atoms and then emitted at the same frequency? Or is something else going on?
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DrChinese is offline
Jun7-11, 12:41 PM
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Absorption/re-emission is not an accurate manner to describe this. I believe this is in the General Physics FAQ. ZapperZ says in part:

"The process of describing light transport via the quantum mechanical description isn't trivial. The use of photons to explain such process involves the understanding of not just the properties of photons, but also the quantum mechanical properties of the material itself (something one learns in Solid State Physics). So this explanation will attempt to only provide a very general and rough idea of the process.

A common explanation that has been provided is that a photon moving through the material still moves at the speed of c, but when it encounters the atom of the material, it is absorbed by the atom via an atomic transition. After a very slight delay, a photon is then re-emitted. This explanation is incorrect and inconsistent with empirical observations. If this is what actually occurs, then the absorption spectrum will be discrete because atoms have only discrete energy states. Yet, in glass for example, we see almost the whole visible spectrum being transmitted with no discrete disruption in the measured speed. In fact, the index of refraction (which reflects the speed of light through that medium) varies continuously, rather than abruptly, with the frequency of light."

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