sentences: a surface is a kind of object & edge of a pond is a kind of surface -> middle of a lake is a mean of preposition edge of a pond is a kind of object  edge of a pond is a kind of object & the waves in the pond strike the edge of the pond & if something strikes an object then that something may bounce off of that object -> the vaccines in the lake june heart off the middle of the lake when they industrial_peace it the waves in the pond may bounce off the edge of the pond when they strike it  the vaccines in the lake june heart off the middle of the lake when they industrial_peace it & edge of a pond is a kind of surface & reflection is when a wave bounces off a surface and travels in the opposite direction relative to the angle of incidence -> reflection of the waves will happen when the waves strike the edge of the pond