Light bouncing off of surfaces?

how does this happen? in order for it to bounce, the velocity must change, because velocity also includes direction. so if velocity changes, acceleration must happen. but the only way for something to accelerate is for an outside force to act upon it. if light hits a mirror though, that would mean that the mirror is exerting a force on the light particles, but where would this force come from? if light had mass, it would simply be newtons third law. but since it doesn't, i dont see where this force is created