Definition of focus

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Focus (n.) 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 constant.

Lern More About Focus

Camera Obscura :: Camera obscura () An apparatus in which the images of external objects, formed by a convex lens or a concave mirror, are thrown on a paper or other white surface placed in the focus of the lens or mirror within a darkened chamber, or box, so that the outlines may be traced..
Focimeter :: Focimeter (n.) An assisting instrument for focusing an object in or before a camera.
Focalization :: Focalization (n.) The act of focalizing or bringing to a focus, or the state of being focalized..
Focal :: Focal (a.) Belonging to,or concerning, a focus; as, a focal point..
Aberration :: Aberration (n.) The convergence to different foci, by a lens or mirror, of rays of light emanating from one and the same point, or the deviation of such rays from a single focus; called spherical aberration, when due to the spherical form of the lens or mirror, such form giving different foci for central and marginal rays; and chromatic aberration, when due to different refrangibilities of the colored rays of the spectrum, those of each color having a distinct focus..
Collimator :: Collimator (n.) A tube having a convex lens at one end and at the other a small opening or slit which is at the principal focus of the lens, used for producing a beam of parallel rays; also, a lens so used..
Corradiate :: Corradiate (v. t.) To converge to one point or focus, as light or rays..
Directrix :: Directrix (n.) A straight line so situated with respect to a conic section that the distance of any point of the curve from it has a constant ratio to the distance of the same point from the focus.
Eccentricity :: Eccentricity (n.) The ratio of the distance between the center and the focus of an ellipse or hyperbola to its semi-transverse axis.
Focalize :: Focalize (v. t.) To bring to a focus; to focus; to concentrate.
Hypermetropy :: Hypermetropy (n.) A condition of the eye in which, through shortness of the eyeball or fault of the refractive media, the rays of light come to a focus behind the retina; farsightedness; -- called also hyperopia. Cf. Emmetropia..
Concentre :: Concentre (v. t.) To draw or direct to a common center; to bring together at a focus or point, as two or more lines; to concentrate..
Image :: Image (n.) The figure or picture of any object formed at the focus of a lens or mirror, by rays of light from the several points of the object symmetrically refracted or reflected to corresponding points in such focus; this may be received on a screen, a photographic plate, or the retina of the eye, and viewed directly by the eye, or with an eyeglass, as in the telescope and microscope; the likeness of an object formed by reflection; as, to see one's image in a mirror..
Amasthenic :: Amasthenic (a.) Uniting the chemical rays of light into one focus, as a certain kind of lens; amacratic..
Focused :: Focused (imp. & p. p.) of Focu.
Convergent :: Convergent (a.) tending to one point of focus; tending to approach each other; converging.
Sunglow :: Sunglass (n.) A convex lens of glass for producing heat by converging the sun's rays into a focus.
Focus :: Focus (n.) A central point; a point of concentration.
Diaphragm :: Diaphragm (n.) A plate with an opening, which is generally circular, used in instruments to cut off marginal portions of a beam of light, as at the focus of a telescope..
Focus :: Focus (n.) 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..
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