Editing Reflection (physics) (section)

===Laws of reflection===
[[Image:Fényvisszaverődés.jpg|An example of the law of reflection|thumb|right]]
{{Main|Specular reflection}}
If the reflecting surface is very smooth, the reflection of light that occurs is called specular or regular reflection. The laws of reflection are as follows:
#The incident ray, the reflected ray and the normal to the reflection surface at the point of the incidence lie in the same [[plane of incidence|plane]].
#The angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal.
#The reflected ray and the incident ray are on the opposite sides of the normal.

These three laws can all be derived from the [[Fresnel equations]].

====Mechanism====

[[File:Reflection of a quantum particle.webm|thumb|2D simulation: reflection of a quantum particle. White blur represents the probability distribution of finding a particle in a given place if measured.]]

In [[Classical electromagnetism|classical electrodynamics]], light is considered as an electromagnetic wave, which is described by [[Maxwell's equations]]. Light waves incident on a material induce small oscillations of [[Dielectric polarization|polarisation]] in the individual atoms (or oscillation of electrons, in metals), causing each particle to radiate a small secondary wave in all directions, like a [[dipole antenna]]. All these waves add up to give specular reflection and refraction, according to the [[Huygens–Fresnel principle]].

In the case of dielectrics such as glass, the electric field of the light acts on the electrons in the material, and the moving electrons generate fields and become new radiators. The refracted light in the glass is the combination of the forward radiation of the electrons and the incident light. The reflected light is the combination of the backward radiation of all of the electrons.

In metals, electrons with no binding energy are called free electrons. When these electrons oscillate with the incident light, the phase difference between their radiation field and the incident field is π (180°), so the forward radiation cancels the incident light, and backward radiation is just the reflected light.

Light–matter interaction in terms of photons is a topic of [[quantum electrodynamics]], and is described in detail by [[Richard Feynman]] in his popular book ''[[QED (book)|QED: The Strange Theory of Light and Matter]]''.