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.
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2. (Bot.) A radiating part of a 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.
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3. (Zool.)
(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.
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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.
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5. Sight; perception; vision; -- from an old theory of
vision, that sight was something which proceeded from the
eye to the object seen.
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All eyes direct their rays
On him, and crowds turn coxcombs as they gaze.
--Pope.
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6. (Geom.) One of a system of diverging lines passing through
a point, and regarded as extending indefinitely in both
directions. See Half-ray.
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Bundle of rays. (Geom.) See Pencil of rays, below.
Extraordinary ray (Opt.), that one of 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.
Roentgen ray, R["o]ntgen ray (r[~e]nt"g[e^]n r[=a]`)
(Phys.), a form of electromagnetic radiation generated in
a very highly exhausted vacuum tube by an electrical
discharge; now more commonly called X-ray. It is
composed of electromagnetic radiation of wavelength
shorter than that of ultraviolet light but longer than
that of gamma rays. 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
X-rays, radiographs, sciagraphs, X-ray photographs,
radiograms. So called from the discoverer, W. C.
R["o]ntgen.
X ray, the R["o]ntgen ray; -- so called by its discoverer
because of its enigmatical character, x being an algebraic
symbol for an unknown quantity.
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