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A reflection through an axis. In mathematics, a reflection (also spelled reflexion) [1] is a mapping from a Euclidean space to itself that is an isometry with a hyperplane as the set of fixed points; this set is called the axis (in dimension 2) or plane (in dimension 3) of reflection.
Likewise, (x, −y) are the coordinates of its reflection across the first coordinate axis (the x-axis). In more generality, reflection across a line through the origin making an angle with the x-axis, is equivalent to replacing every point with coordinates (x, y) by the point with coordinates (x′,y′), where
The term reflection is loose, and considered by some an abuse of language, with inversion preferred; however, point reflection is widely used. Such maps are involutions, meaning that they have order 2 – they are their own inverse: applying them twice yields the identity map – which is also true of other maps called reflections.
When reflection occurs from thin layers of material, internal reflection effects can cause the reflectance to vary with surface thickness. Reflectivity is the limit value of reflectance as the sample becomes thick; it is the intrinsic reflectance of the surface, hence irrespective of other parameters such as the reflectance of the rear surface.
Diagram showing vectors used to define the BRDF. All vectors are unit length. points toward the light source. points toward the viewer (camera). is the surface normal.. The bidirectional reflectance distribution function (BRDF), symbol (,), is a function of four real variables that defines how light from a source is reflected off an opaque surface. It is employed in the optics of real-world ...
In telecommunications and transmission line theory, the reflection coefficient is the ratio of the complex amplitude of the reflected wave to that of the incident wave. The voltage and current at any point along a transmission line can always be resolved into forward and reflected traveling waves given a specified reference impedance Z 0.
The product of two rotations or two reflections is a rotation; the product of a rotation and a reflection is a reflection. So far, we have considered D n to be a subgroup of O(2) , i.e. the group of rotations (about the origin) and reflections (across axes through the origin) of the plane.
Grazing incidence diffraction is used in X-ray spectroscopy and atom optics, where significant reflection can be achieved only at small values of the grazing angle. Ridged mirrors are designed to reflect atoms coming at a small grazing angle. This angle is usually measured in milliradians. In optics, there is Lloyd's mirror.