Source : Webster's Revised Unabridged Dictionary (1913)

Rontgen ray \R["o]ntgen ray\ (Physics)
   Any of the rays produced when cathode rays strike upon
   surface of a solid (as the wall of the vacuum tube).
   R["o]ntgen rays are noted for their penetration of many
   opaque substances, as wood and flesh, their action on
   photographic plates, and their fluorescent effects. They were
   called {X rays} by their discoverer, W. K. R["o]ntgen. They
   also ionize gases, but cannot be reflected, or polarized, or
   deflected by a magnetic field. They are regarded as
   nonperiodic, transverse pulses in the ether. They are used in
   examining opaque objects, as for locating fractures or
   bullets in the human body.

Ray \Ray\, n. [OF. rai, F. rais, fr. L. radius a beam or ray,
   staff, rod, spoke of a wheel. Cf. {Radius}.]
   1. One of a number of lines or parts diverging from a common
      point or center, like the radii of a circle; as, a star of
      six rays.

   2. (Bot.) A radiating part of the flower or plant; the
      marginal florets of a compound flower, as an aster or a
      sunflower; one of the pedicels of an umbel or other
      circular flower cluster; radius. See {Radius}.

   3. (Zo["o]l.)
      (a) One of the radiating spines, or cartilages, supporting
          the fins of fishes.
      (b) One of the spheromeres of a radiate, especially one of
          the arms of a starfish or an ophiuran.

   4. (Physics)
      (a) A line of light or heat proceeding from a radiant or
          reflecting point; a single element of light or heat
          propagated continuously; as, a solar ray; a polarized
          ray.
      (b) One of the component elements of the total radiation
          from a body; any definite or limited portion of the
          spectrum; as, the red ray; the violet ray. See Illust.
          under {Light}.

   5. Sight; perception; vision; -- from an old theory of
      vision, that sight was something which proceeded from the
      eye to the object seen.

            All eyes direct their rays On him, and crowds turn
            coxcombs as they gaze.                --Pope.

   6. (Geom.) One of a system of diverging lines passing through
      a point, and regarded as extending indefinitely in both
      directions. See {Half-ray}.

   {Bundle of rays}. (Geom.) See {Pencil of rays}, below.

   {Extraordinary ray} (Opt.), that one or two parts of a ray
      divided by double refraction which does not follow the
      ordinary law of refraction.

   {Ordinary ray} (Opt.) that one of the two parts of a ray
      divided by double refraction which follows the usual or
      ordinary law of refraction.

   {Pencil of rays} (Geom.), a definite system of rays.

   {Ray flower}, or {Ray floret} (Bot.), one of the marginal
      flowers of the capitulum in such composite plants as the
      aster, goldenrod, daisy, and sunflower. They have an
      elongated, strap-shaped corolla, while the corollas of the
      disk flowers are tubular and five-lobed.

   {Ray point} (Geom.), the common point of a pencil of rays.

   {R["o]ntgen ray}(Phys.), a kind of ray generated in a very
      highly exhausted vacuum tube by the electrical discharge.
      It is capable of passing through many bodies opaque to
      light, and producing photographic and fluorescent effects
      by which means pictures showing the internal structure of
      opaque objects are made, called radiographs, or sciagraphs