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, the reflected ray, and the normal all lie in the same plane. This means that the reflection occurs in a single, flat plane. This principle applies to all types of reflection, whether it is specular reflection from a smooth surface like a mirror, or diffuse reflection from a rough surface. In specular reflection, parallel incident rays produce parallel reflected rays, which is why mirrors form clear images. In diffuse reflection, parallel incident rays scatter in many directions, which is why we can see non-shiny objects. The heijastussääntö is crucial for understanding how we see objects and for the design of optical instruments such as telescopes and cameras.