Falling light. According to general relativity and the equivalence principle, light is bent by gravity. Consider two tall, perfectly reflecting mirrors exactly 7 m apart and facing each other. A beam of light is directed horizontally through a hole in one of the mirrors 13 m above the ground. (a) Determine the time it takes for the light to strike the ground. b) The light will undergo N reflections (i.e., N/2 reflections from each mirror) before it strikes the ground. Find N.