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Q: How does the reflectivity of a light-source change when it is switched on/off?

Consider a light-source like an red LED with some white light shining on it. When the LED's switched off, it's going to be absorbing some of the white light (I'm fairly certain of this) and it won't appear reflective. But when the LED is switched on, does it reflect any of the white light? Furthermore, would the electrons in the LED that emit red light start reflecting red wavelengths from the white light?

I was asked this question earlier today and dismissed it as silly but after reading up on it for a while, I realised I couldn't give a good answer. This is my first time posting on this stackexchange so thanks for letting me ask this question.

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    $\begingroup$ I would expect that the reflectivity of a LED doesn't change due to its being on or off. Why should it? Running a small current through an LED doesn't cause its electronic structure or bandgap to change. $\endgroup$ – Samuel Weir May 11 '17 at 19:05
  • $\begingroup$ @SamuelWeir Thanks for the response. In answer to 'why should it': as I understand it when an LED is emitting some light, electrons in the LED are emiting photons so are those electrons still capable of absorbing photons and emitting them at the same time? $\endgroup$ – Jam May 11 '17 at 19:10
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    $\begingroup$ I think that that electronic recombination occurs in a very thin layer at the p-n junction of an LED. Conceivably, there might be some small effect on reflectivity but my feeling is that we're talking about very small changes here. Similarly, the reflectivity and emissivity of the tungsten filament in an incandescent light bulb don't suddenly undergo dramatic changes simply because it starts emitting light. There is, however, a temperature dependence to the emissivity of tungsten. $\endgroup$ – Samuel Weir May 11 '17 at 19:46
  • $\begingroup$ @SamuelWeir Wonderful, that answers my question. Thanks :) $\endgroup$ – Jam May 11 '17 at 19:50

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