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lightarrow
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Don't know if this is the correct forum.
While we know that light's phase velocity in a linear medium with refration index n is c/n, what can we say about signal's velocity? If I switch on a laser inside the medium (let's say glass) at t = 0, when will the first photon arrive to a detector placed L metres away? At t = L/(c/n) or at t = L/c or else?
While we know that light's phase velocity in a linear medium with refration index n is c/n, what can we say about signal's velocity? If I switch on a laser inside the medium (let's say glass) at t = 0, when will the first photon arrive to a detector placed L metres away? At t = L/(c/n) or at t = L/c or else?