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Old 19-05-2011, 08:40 PM
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Robh (Rob)
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Join Date: Feb 2009
Location: Blue Mountains, Australia
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Casey,

I think I understand where you're coming from.
This is my viewpoint on the physics involved. Consider light travelling through a denser medium such as glass.

The explanation is based (as Carl mentioned earlier) on both the wave and particle nature (or packet energy) of the light. The atomic structure of glass is such that the packet energy of any photon is absorbed and then re-emitted by constituent atoms rather than being absorbed and held as heat as in opaque materials. Glass atoms will absorb and then re-emit this packet energy in an essentially random chain throughout the glass but in the general direction of the refracted wavefront. It is important to note that any individual photon is reconverted many many times from one energy packet to another from atom to atom through the glass.
Exit photons are not the same ones that entered the glass. Due to the quantum nature of these energy conversions, it is impossible to trace the "path" of an individual photon packet.
The reason light slows down in glass is because of the time lag in passing this packet of energy from atom to atom. The initial bending (refraction) is due to the slowdown in energy transfer of photons in the wavefront nearer the glass compared to the photons still travelling through the air in the same wavefront further from the glass.

Regards, Rob
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