When ψ=0 on impact on the surface of incidence, the photon fully manifest itself as a mass mp with velocity c. When it passes the exit surface in a very thin medium, it is not going to regain ψ as ψ has completely disappeared.
What is this particle that was previously a photon? It has a small mass mp, but no energy density, ψ=0. Does it exist?
If this happens the medium will actually cool when bombarded with photons.
