Editing Corner reflector (section)

==Principle==
[[File:Corner reflector.svg|thumb|220px|Working principle of a corner reflector]]

The incoming ray is reflected three times, once by each surface, which results in a reversal of direction.<ref name="Newman">{{cite book   
  | last = Newman
  | first = William I. 
  | title = Continuum Mechanics in the Earth Sciences
  | publisher = Cambridge University Press
  | date = 2019
  | pages = 6–7
  | url = https://books.google.com/books?id=CWXO_nVRKYMC&pg=PA6
  | isbn = 978-0-521-56289-8}}</ref><ref name="Bernstein">{{cite book   
  | last1 = Bernstein
  | first1 = Matt A.
  |first2=William A. |last2=Friedman
  | title = Thinking About Equations: A Practical Guide for Developing Mathematical Intuition in the Physical Sciences and Engineering
  | publisher = Wiley
  | date = 2011
  | pages = 193
  | url = https://books.google.com/books?id=l8A-VnolePcC&dq=%22corner+reflector&pg=PT193
  | isbn = 978-1-118-21064-2}}</ref>   To see this, the three corresponding normal vectors of the corner's perpendicular sides can be considered to form a [[basis (linear algebra)|basis]] (a [[rectangular coordinate system]]) (''x'', ''y'', ''z'') in which to represent the direction of an arbitrary incoming ray, {{thinsp|[''a'',|''b'',|''c'']}}.  When the ray reflects from the first side, say ''x'', the ray's ''x'' component, ''a'',  is reversed to −''a'' while the ''y'' and ''z'' components are unchanged, resulting in a direction of {{thinsp|[−''a'',|''b'',|''c'']}}.  Similarly, when reflected from side ''y'' and finally from side ''z'', the ''b'' and ''c'' components are reversed. Therefore, the ray direction goes from {{thinsp|[''a'',|''b'',|''c'']}} to {{thinsp|[−''a'',|''b'',|''c'']}} to {{thinsp|[−''a'',|−''b'',|''c'']}} to {{thinsp|[−''a'',|−''b'',|−''c'']}}, and it leaves the corner reflector with all three components of direction exactly reversed. The distance travelled, relative to a plane normal to the direction of the rays, is also equal for any ray entering the reflector, regardless of the location where it first reflects.{{Citation needed|date=March 2013}}
[[File:Reflection-coin-cube-rot.gif|thumb|Animation showing the reflected rays in a corner of a cube (corner reflector principle).]]
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