The reason for light refraction in subatomic level

Question

Can someone explain the reason for light refraction in subatomic level?

Comments

What is "light fracture"?

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sorry i meant light refraction :D @MitchellPorter 

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@VladimirKalitvianski thanks for your answer but now i have another question.

it may sound very silly as any other new question in science.

what would happen if we had 6 quarks in protons and neutrons instead of three?

what would happen then to light refraction ?

and is this situation even possible?

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Proton is a rather compact particle - its "size" is much smaller than any photon wavelength, so normally a photon "sees" a point-like charge $+1$. The proton internals do not participate in photon scarttering separately; rather, they are tightly bound and do not change their initial state. There are heavy particles with more quarks: it is a deyteron, tritium, Helium_3, Helium_4, and the other heavier nuclea. They all act as point charges while photon scattering due to too tight coupling of quarks inside, so normally a photon does not "excite" a nucleus. There are exclusions (see Moessbauer effect), but for your purposes it is well sufficient to consider the nuclea and electrons as point-like charged particles affected with a photon electromagnetic field. It is atomic, molecular, and condensed meduim constituents who "refract" the photon because the binding energy in them is comparable with that of photon.