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In thin-film interference and in glass fibers refraction is involved. Depending on the angle of which a light ray enters the material it will be reflected or transmitted. The refraction depends on the different materials like air and water, glass or oil.

But as far as I know the reflection happens within the material of the thin-film or the glass. So from that point of view that photon haven't 'seen' or 'felt' the material on the other side of that material which refraction index would reflect them. So when a photon is reflected before he 'knows' the other material (as he is reflected by the atoms of the same material as he went in) how does he 'know' that he 'has' to bounce back?

Vishnu JK
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Marijn
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1 Answers1

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As mentioned in comments, a photon is "delocalised", so it feels the whole system. You may imagine a photon as a long-long wave (to have a defined frequency) and as such it interacts with the whole material. More strictly, one can say that the source of photon is the whole set of charges, so the photon is a collective mode of excitation of a given system. Thus it becomes natural that a photon feels more than we naively think. The notion of a separate photon in space is a poor physical picture.

Vladimir Kalitvianski
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