heijastussäännön
Heijastussääntö, known in English as the law of reflection, describes the behavior of light when it bounces off a surface. It is a fundamental principle in optics. The rule states that the angle of incidence is equal to the angle of reflection. The angle of incidence is the angle between the incoming ray of light and the normal to the surface at the point of incidence. The normal is an imaginary line perpendicular to the surface. Similarly, the angle of reflection is the angle between the reflected ray of light and the normal.
In addition to the equality of angles, the law of reflection also specifies that the incident ray,