Editing Specular reflection (section)

== Consequences ==
=== Internal reflection ===
When light is propagating in a material and strikes an interface with a material of lower [[index of refraction]], some of the light is reflected. If the angle of incidence is greater than the [[critical angle (optics)|critical angle]], [[total internal reflection]] occurs: all of the light is reflected. The critical angle can be shown to be given by
: <math>\theta_\text{crit} = \arcsin\!\left(\frac{n_2}{n_1}\right)\!.</math>

=== Polarization ===
When light strikes an interface between two materials, the reflected light is generally partially [[Polarization (waves)|polarized]]. However, if the light strikes the interface at [[Brewster's angle]], the reflected light is ''completely'' linearly polarized parallel to the interface. Brewster's angle is given by
: <math>\theta_\mathrm{B} = \arctan\!\left(\frac{n_2}{n_1}\right)\!.</math>

=== Reflected images ===
{{See also|Mirror image#In three dimensions}}
The image in a flat mirror has these features:
* It is the same distance behind the mirror as the object is in front.
* It is the same size as the object.
* It is the right way up (erect).
* It is reversed.
* It is ''virtual'', meaning that the image appears to be behind the mirror, and cannot be projected onto a screen.

The reversal of images by a plane mirror is perceived differently depending on the circumstances. In many cases, the image in a mirror appears to be reversed from left to right. If a flat mirror is mounted on the ceiling it can appear to reverse ''up'' and ''down'' if a person stands under it and looks up at it. Similarly a car turning ''left'' will still appear to be turning ''left'' in the rear view mirror for the driver of a car in front of it. The reversal of directions, or lack thereof, depends on how the directions are defined. More specifically a mirror changes the [[Cartesian coordinate system#In three dimensions|handedness]] of the coordinate system, one axis of the coordinate system appears to be reversed, and the [[Chirality (mathematics)|chirality]] of the image may change. For example, the image of a right shoe will look like a left shoe.