Physics Explanation:
In this picture, I just used a laser pointer and pointed it towards a mirror at an angle. (By turning off the light and spraying water in the air we can see the actual beams.) This mirror is simply a straight mirror so the beam of light coming from the right side of the picture hits the mirror and bounces off to the left as we can see in the picture.
This relates to what we've been doing in class regarding our law of reflection, Oi = Or. From my point of view, there is a tangent line flat across the mirror and a normal line (perpendicular) coming straight out towards us. The 1st light beam (angle of incidence) on the right hits the mirror at an angle going left and immediately bounces off at the same angle (angle of reflection). These two light beams are split by the normal line between them. Basically, the distance from each beam to the normal line is the same.