More On Waves
Light is a wave in that it exhibits the same properties as waves, such as reflection in which the angle of incidence at which light strikes a surface (measured from the normal or 90 degrees) equals the angle of reflection:
Light also exhibits interference, which occurs when crests or troughs from opposing waves meet. When two troughs or two crests meet the interference is called constructive. When a crest and trough meet they cancel each other out, resulting in destructive interference.