>>7
According to the equations of general relativity a black hole has zero volume. However, according to quantum mechanics, it's impossible for an object to have zero size. This means that the black hole would just be as small as physically possible but not a singularity.
So really we've got two extremely well tested theories saying two completely different things and until we can come up with something better we really don't know much about the size of a black hole.
The reason that black holes, or gravity in general, effect light is because gravity bends space. And since light is traveling through space, it's trajectory also get's altered.