Quick question about radiation pressure?

[jeebs]

it's apparently well known that light can exert pressure on a surface, which could be used as a light sail or whatever they are called, to accelerate space ships. however, light is a transverse wave, so when it interacts with charged particles it will accelerate them in a direction perpendicular to its trajectory, right?

so how does radiation pressure happen, if I'm right in assuming that the pressure is due to the momentum of the photon, which points in the direction that the photon is travelling?
why does a transverse excitation produce a forward-acting force?

 

[kcdodd]

I would analyse in a simple case of an em wave reflecting off of a conductor. The electric field is ideally zero at the interface so it can't exert much force anyway. However, the magnetic field is discontinuous at the surface. That discontinuity is created by a surface current. If you do JxB then you get a force which is your pressure.