Law of Reflection
Law of reflection: The angle of incidence is equal to the angle of reflection.
Pool tables make a great example of the law of reflection. This law tells you that the angle at which the ball strikes the rail is equal to the angle the ball bounces off at. In other words, if the ball approaches the rail at a 30º angle, it will bounce off at a 30º angle as well. As you can see in the picture above, this creates a situation with similar triangles.
Billiards players really do estimate and measure similar triangles when setting up their shots.