Single Photon Hits A Linear Polarizer, What Happens? If a linear polarized single photon strikes a linear polarizer such that its polarization is at 45 degrees to the polarization axis of the polarizer, what happens?
There is a nearly 50% chance that the photon is transmitted, and assuming it is transmitted, it somehow rotates its polarization to match that of the polarizer axis. But the photon has energy defined by E=hv before and after it encounters the polarizer.  So it cannot lose energy by projecting its amplitude onto the polarization axis, as per the normal explanation.
Also assuming the linear polarizer is a dichroic type, then I understand that this means the long molecules in the film have their long axis aligned perpendicular to the polarization axis - so how does the photon encounter the molecules.  Is it absorbed and then re-emitted orthogonal to the molecular axis somehow?
 A: Since you are talking about photons, you are also talking about quantum mechanics.  In the language of QM, the incoming photon induces a transition to a virtual state of a molecule in the polarizer.  When the molecule returns to the ground state, a photon of rotated polarization is emitted.
This transition to a virtual state is not absorption.  The energy of the photon does not have to be anywhere near the energy of a molecular transition.  The photon and the molecule find themselves in a state of mixed photon and molecule character.  This state retains its coherence properties, and the phase of the outgoing photon is related to the phase of the incoming photon, and its frequency is identical to that of the incoming photon.  
In real absorption, something (like a collision) interrupts the coherence of the mixed state, which could lead to the molecule finding itself in a true excited state.  This can only happen if the energy of the photon matches the energy of the excited state.  In that case, we say the photon has been absorbed.  The molecule will eventually spontaneously drop back to the ground state emitting a photon, but that photon will have no fixed phase relationship with the original, and might not have the same frequency.  
