Test particles and electromagnetic fields in exact gravitational wave spacetimes

We consider the propagation of massive neutral test particles and electromagnetic waves in the background of radiation
fields that are generated either by an exact gravitational wave or an exact electromagnetic wave
in the framework of general relativity.
The features of the scattering of massive particles are analysed and compared, depending on the nature
 of the radiation field considered. To study the light scattering by these radiation fields we develop the optical
 medium analogy of the associated background, allowing for a comparison of the distinct optical properties of
the equivalent optical media.
We are able to identify certain detectable observational consequences arising from our analysis,
 e.g., the deflection and delay of photon beams, the response of a Michelson interferometer to
gravitational waves beyond linear approximation, etc.
Lastly, we discuss some interesting physical effects related to light propagation in the
 background of colliding gravitational waves.