Recently, a simple solution of the vacuum Einstein-Maxwell field equat
ions was given describing a plane electromagnetic shock wave sharing i
ts wave front with a plane gravitational impulse wave. We present here
an exact solution of the vacuum Einstein-Maxwell field equations desc
ribing the head-on collision of such a wave with a plane gravitational
impulse wave. The solution has the Penrose-Khan solution and a soluti
on obtained by Griffiths as separate limiting cases.