conjugate mirrors

Conjugate \Con"ju*gate\, a. [L. conjugatus, p. p. or conjugare
   to unite; con- + jugare to join, yoke, marry, jugum yoke;
   akin to jungere to join. See {Join}.]
   1. United in pairs; yoked together; coupled.
      [1913 Webster]

   2. (Bot.) In single pairs; coupled.
      [1913 Webster]

   3. (Chem.) Containing two or more compounds or radicals
      supposed to act the part of a single one. [R.]
      [1913 Webster]

   4. (Gram.) Agreeing in derivation and radical signification;
      -- said of words.
      [1913 Webster]

   5. (Math.) Presenting themselves simultaneously and having
      reciprocal properties; -- frequently used in pure and
      applied mathematics with reference to two quantities,
      points, lines, axes, curves, etc.
      [1913 Webster]

   {Conjugate axis of a hyperbola} (Math.), the line through the
      center of the curve, perpendicular to the line through the
      two foci.

   {Conjugate diameters} (Conic Sections), two diameters of an
      ellipse or hyperbola such that each bisects all chords
      drawn parallel to the other.

   {Conjugate focus} (Opt.) See under {Focus}.

   {Conjugate mirrors} (Optics), two mirrors so placed that rays
      from the focus of one are received at the focus of the
      other, especially two concave mirrors so placed that rays
      proceeding from the principal focus of one and reflected
      in a parallel beam are received upon the other and brought
      to the principal focus.

   {Conjugate point} (Geom.), an acnode. See {Acnode}, and
      {Double point}.

   {Self-conjugate triangle} (Conic Sections), a triangle each
      of whose vertices is the pole of the opposite side with
      reference to a conic.
      [1913 Webster]