Reflection of Light

The angle of incidence equals the angle of reflection.

Discussion

In this movie a mirror is placed at the back of a semi-circular dish filled with water and a bit of milk to make the beam from a laser pointer visible from above. As the laser pointer is moved around the dish, you can see that the angle at which the beam is reflected by the mirror is equal to the angle of incidence, the angle at which the beam strikes the mirror. When a linear wave strikes a flat barrier at an angle, it is reflected at that same angle.