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I would like to understand the difference between reflection of light and re emission.

Indeed in both case an observer far from the object will se an electromagnetic field coming to him.

When we take a perfect conductor an a E.M wave going to it, we know that the wave is "reflected" but can we also see it in the way that the material absorbed the light and re emitted it ?

Is the difference based on the fact that in re emission the energy is stored for a finite amount of time in the material and the re emitted as a ray whereas in reflection the energy of the incident beam is never stored by the material ?

Thank you for your answers.

StarBucK
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1 Answers1

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If by re-emission you mean fluorescence, than the key difference is in coherence, which is related to what you've suggested. In the case of idealistic reflection each oscillator(atom) in the material moves in phase(with certain delay) with incident light, i.e. coherence is preserved. The result of the interference from all the oscillators is reflected beam, which, due to coherence, has a well defined direction (for good surface and directed incident light).

In the case of fluorescence each oscillator will re-emit after certain delay, probabilistically and not correlated with other oscillators in the crystal. Thus the radiation will not be directed.

Ivan Madan
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