Search:focus -> FOCUS
focus
f o c u s hex:#102;#111;#99;#117;#115;
The Salt of the World?
- 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.
- 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.
- Focus - n. - A central point; a point of concentration.
- Focus - v. t. - To bring to a focus; to focalize; as, to focus a camera.
- Focused - imp. & p. p. - of Focus
- Focuses - pl. - of Focus
- Focusing - p. pr. & vb. n. - of Focus
- Reticule - n.. - A system of wires or lines in the focus of a telescope or other instrument; a reticle.
- 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.
- 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.
- 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.
- 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.
- Polar - n. - The right line drawn through the two points of contact of the two tangents drawn from a given point to a given conic section. The given point is called the pole of the line. If the given point lies within the curve so that the two tangents become imaginary, there is still a real polar line which does not meet the curve, but which possesses other properties of the polar. Thus the focus and directrix are pole and polar. There are also poles and polar curves to curves of higher degree than the second, and poles and polar planes to surfaces of the second degree.
- Micrometer - n. - An instrument, used with a telescope or microscope, for measuring minute distances, or the apparent diameters of objects which subtend minute angles. The measurement given directly is that of the image of the object formed at the focus of the object glass.
- Latus rectum - - The line drawn through a focus of a conic section parallel to the directrix and terminated both ways by the curve. It is the parameter of the principal axis. See Focus, and Parameter.
- Myopia - n. - Nearsightedness; shortsightedness; a condition of the eye in which the rays from distant object are brought to a focus before they reach the retina, and hence form an indistinct image; while the rays from very near objects are normally converged so as to produce a distinct image. It is corrected by the use of a concave lens.
- 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.
- 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.
- Eccentricity - n. - The ratio of the distance between the center and the focus of an ellipse or hyperbola to its semi-transverse axis.
- 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.
- Focus - v. t. - To bring to a focus; to focalize; as, to focus a camera.