|Message: Re: propagation speed of optical photons||Not Logged In (login)|
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Ok. To answer my own question. Geant 4 propagates the optical photons with the group velocity not the phase velocity (c/n), where the group velocity is
vg = c/(n(E)+dn/d(log(E))
The plot compares phase velocity, group velocity and the velocity with which optical photons are propagated in PbF4.
Looks like geant 4 does a good job.