Light is an electromagnetic wave that exhibits both wave and matter-like properties yes? I was wondering what happens to light when it reflects off a mirror. If a tennis ball is thrown at a wall, the moment of contact between the ball and the wall is very brief, so the deceleration rate is very, very high right? Say the ball was travelling 20ms^-1 then bounces back at around -19ms^-1, making a difference of 39ms^-1. The length of time the ball contacts the wall is around 0.02s (for the sake of example). Then the deceleration would be 1950ms^-2. There is a point in time where the ball is simply stationary. Light travels at around 299,792,458ms^-1. The moment of 'contact' is near negligible, most likely in the picoseconds. Even so, there must be a measure of deceleration for light whether it is a particle (matter) or wave (radiation). If this is the case, then what kind of properties would light have at the inevitable point in time of 0 velocity? If I have it all wrong and there is a separate set of physical laws governing EM radiation, what is it?