you are going to have to do a lot more than this if you want a proper 'flash' like maybe key an area light or ambient light so the whole room lights up as the flash goes off and you will have to map the fog (thats the picture here) to get that look when light passes through glass, you know have a look at a torch beam on the wall, its not all flat light, theres highlights, dark spots, ect.., anyway, you need to add fog for obvious reasons.., so you get a beam of light.
take it easy and life will be easy