Definition of Focuses. Meaning of Focuses. Synonyms of Focuses
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Definition of Focuses
FocusesFocus Fo"cus, n.; pl. E. Focuses, L. Foci. [L. focus
hearth, fireplace; perh. akin to E. bake. Cf. Curfew,
Fuel, Fusil the firearm.]
1. (Opt.) A point in which the rays of light meet, after
being reflected or refrcted, and at which the image is
formed; as, the focus of a lens or mirror.
2. (Geom.) A point so related to a conic section and certain
straight line called the directrix that the ratio of the
distace between any point of the curve and the focus to
the distance of the same point from the directrix is
Note: Thus, in the ellipse FGHKLM, A is the focus and CD the
directrix, when the ratios FA:FE, GA:GD, MA:MC, etc.,
are all equal. So in the hyperbola, A is the focus and
CD the directrix when the ratio HA:HK is constant for
all points of the curve; and in the parabola, A is the
focus and CD the directrix when the ratio BA:BC is
constant. In the ellipse this ratio is less than unity,
in the parabola equal to unity, and in the hyperbola
greater than unity. The ellipse and hyperbola have each
two foci, and two corresponding directrixes, and the
parabola has one focus and one directrix. In the
ellipse the sum of the two lines from any point of the
curve to the two foci is constant; that is:
AG+GB=AH+HB; and in the hyperbola the difference of the
corresponding lines is constant. The diameter which
passes through the foci of the ellipse is the major
axis. The diameter which being produced passes through
the foci of the hyperbola is the transverse axis. The
middle point of the major or the transverse axis is the
center of the curve. Certain other curves, as the
lemniscate and the Cartesian ovals, have points called
foci, possessing properties similar to those of the
foci of conic sections. In an ellipse, rays of light
coming from one focus, and reflected from the curve,
proceed in lines directed toward the other; in an
hyperbola, in lines directed from the other; in a
parabola, rays from the focus, after reflection at the
curve, proceed in lines parallel to the axis. Thus rays
from A in the ellipse are reflected to B; rays from A
in the hyperbola are reflected toward L and M away from
3. A central point; a point of concentration.
Aplanatic focus. (Opt.) See under Aplanatic.
Conjugate focus (Opt.), the focus for rays which have a
sensible divergence, as from a near object; -- so called
because the positions of the object and its image are
Focus tube (Phys.), a vacuum tube for R[oe]ntgen rays in
which the cathode rays are focused upon the anticathode,
for intensifying the effect.
Principal, or Solar, focus (Opt.), the focus for parallel
Meaning of Focuses from wikipedia
- 2010. "Focus
on his label
a.Fam Entertainment". The Hype Machine. May 25, 2009. Retrieved March
3, 2010. Focus
… at AllMusic...
(band), a Christian hardcore
(album), a 1999 album
by Billy Cobham
" (song), a song by Wale "Focused"...
, or foci may refer
name of the Adelaide Fringe
in South Australia Focus
, a 1962 TV film...
an optical system
to minimize defocus aberration Focusing
(psychotherapy), a psychotherapeutic technique Focus
- Focus Plays Focus
is the first studio album
rock band Focus
1970 on Imperial
Records. It is the only album recorded
- InFocus Corporation
is an American privately owned company based
in the state
of Oregon. Founded
in 1986, the company
develops, manufactures, and distributes...
- The Ford Focus
is a compact
car (C-segment in Europe) manufactured
by the Ford Motor Company
and created under Alexander
Trotman's Ford 2000 plan, which...
- optics, a focus
, also called
point, is a point where light
from a point
on the object
- of the progressive
rock band Focus consists
of 11 studio
albums, 1 compilation
album, 6 live albums, and 8 singles. "Focus Album
Top 100". Kent, David...
is a fourth-generation programming language
(4GL) computer programming language
and development environment
that is used to build database
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