define focus in physics

The arms of the hyperbola approach asymptotic lines and the 'right-hand' arm of one branch of a hyperbola meets the 'left-hand' arm of the other branch of a hyperbola at the point at infinity; this is based on the principle that, in projective geometry, a single line meets itself at a point at infinity. The tangential equations for the circular points at infinity are X+iY=0 and X−iY=0 so Q=X2+Y2. Moreover, the Pluto-Charon system moves in an ellipse around its barycenter with the Sun, as does the Earth-Moon system (and every other planet-moon system or moonless planet in the solar system). There are two sets of m lines which will have m2 points of intersection, with exceptions in some cases due to singularities, etc. a campaign that focused on economic issues. The summit is expected to focus on arms control. Therefore, the tangential equation for a conic with the given foci is X2-1+c(X2+Y2)=0, or (1+c)X2+cY2=1 where c is an arbitrary constant. focus in Physics topic. In case of concave lens, the rays of light parallel to the principal axis appear to diverge from a point on the principal axis called principal focus. It is also possible to describe all the conic sections as loci of points that are equidistant from a single focus and a single, circular directrix. draw a bead on To aim at carefully, to line up in the sight of one’s gun; to zero in on a person or thing. All content on this website, including dictionary, thesaurus, literature, geography, and other reference data is for informational purposes only. fo‧cus1 /ˈfəʊkəs $ ˈfoʊ-/ S3 W2 AWL verb (focused or focussed, focusing or focussing) 1 give attention to something [ intransitive, transitive] ATTENTION. Thus, for instance, the minor planet Pluto's largest moon Charon has an elliptical orbit which has one focus at the Pluto-Charon system's barycenter, which is a point that is in space between the two bodies; and Pluto also moves in an ellipse with one of its foci at that same barycenter between the bodies. صاف تصویر لینے کے لۓ کسی کیمرہ یا دوربین وغیرہ کو ٹھیک کرنا. Medical Definition of focus (Entry 1 of 2) 1 a : a point at which rays (as of light, heat, or sound) converge or from which they diverge or appear to diverge specifically : the point where the geometrical lines or … Another definition of an ellipse uses affine transformations: . Any ellipse is an affine image of the unit circle with equation + =. Learn more. To generate a hyperbola, the radius of the directrix circle is chosen to be less than the distance between the center of this circle and the focus; thus, the focus is outside the directrix circle. Though this meaning persists, the expression has been extended to include figurative application in various nonballistic contexts as evidenced in this example by J. N. Leonard cited in Webster’s Third: … bird-dogs zeroing in on coveys of hidden quail. It is also possible to describe all conic sections in terms of a single focus and a single directrix, which is a given line not containing the focus. Remember to focus the camera / the picture before taking the photograph. A circle can also be defined as the circle of Apollonius, in terms of two different foci, as the set of points having a fixed ratio of distances to the two foci. Thus, a circle can be more simply defined as the locus of points each of which is a fixed distance from a single given focus. (in physics…. the focus of the campaign for black rights. By comparison, the Earth's Moon moves in an ellipse with one of its foci at the barycenter of the Moon and the Earth, this barycenter being within the Earth itself, while the Earth (more precisely, its center) moves in an ellipse with one focus at that same barycenter within the Earth. The case H=0 can be eliminated as degenerate, so the tangential equation of C can be written as P+fQ=0 where f is an arbitrary polynomial of degree m−2. The tangential equations are X+1=0 and X−1=0 so P= X2-1=0. Originally, zero in referred to adjusting the sights of a gun to the zero or horizontal line so that when aimed and fired at a target, the projectile will hit it dead center. In both cases the barycenter is well within the body of the Sun. Dictionary, Encyclopedia and Thesaurus - The Free Dictionary, the webmaster's page for free fun content, Air Force Intelligence Surveillance and Reconnaissance, Focal distance, or length, of a lens or mirror, Focus Ask questions Connect ideas Try to picture, he/she/it will have been focusing/focussing. A circle is the special case of an ellipse in which the two foci coincide with each other. Principal focus definition is - the focus for a beam of incident rays parallel to the axis. If the weights are equal, the special case of an ellipse results. The barycenter is about three-quarters of the distance from Earth's center to its surface. Conic section § Eccentricity, focus and directrix, https://en.wikipedia.org/w/index.php?title=Focus_(geometry)&oldid=973104839, Creative Commons Attribution-ShareAlike License, This page was last edited on 15 August 2020, at 11:15. Principal focus (F): The point on the principal axis where the rays of light parallel to the principal axis converge after refraction through the convex lens. These points of intersection are the defined to be the foci of C. In other words, a point P is a focus if both PI and PJ are tangent to C. When C is a real curve, only the intersections of conjugate pairs are real, so there are m in a real foci and m2−m imaginary foci. Let C be a curve of class m and let I and J denote the circular points at infinity. She was the focus of everyone's attention. (The n=2 case is the conventional ellipse.). George Catlin used the expression literally in his treatise on North American Indians (1833). parametric representation. focus definition: 1. the main or central point of something, especially of attention or interest: 2. When C is a conic, the real foci defined this way are exactly the foci which can be used in the geometric construction of C. Let P1, P2, ..., Pm be given as foci of a curve C of class m. Let P be the product of the tangential equations of these points and Q the product of the tangential equations of the circular points at infinity. Two binary stars also move in ellipses sharing a focus at their barycenter; for an animation, see here. The reference is to the bead or front sight of a rifle. Then all the lines which are common tangents to both P=0 and Q=0 are tangent to C. So, by the AF+BG theorem, the tangential equation of C has the form HP+KQ=0. In addition, two foci are used to define the Cassini oval and the Cartesian oval, and more than two foci are used in defining an n-ellipse. Since C has class m, H must be a constant and K but have degree less than or equal to m−2. Pluto's ellipse is entirely inside Charon's ellipse, as shown in this animation of the system. In geometry, focuses or foci (UK: /ˈfoʊkaɪ/, US: /ˈfoʊsaɪ/), singular focus, are special points with reference to which any of a variety of curves is constructed. A Cartesian oval is the set of points for each of which the weighted sum of the distances to two given foci is a constant. The directrix 'circle' becomes a curve with zero curvature, indistinguishable from a straight line. Draw the m tangents to C through each of I and J. a point at which rays of light, heat, or other radiation meet after being refracted or reflected. The weights are equal, the center of the foci is a constant points at (. C has class m and let I and J its second focus at their barycenter ; for animation. As shown in this animation of the directrix moves to the axis shown in this animation of distances... Have degree less than or equal to m−2 is entirely inside Charon 's,. Ellipse in which the two branches of a curve with zero curvature, indistinguishable a. And the ellipse thus generated has its second focus at the center of the foci is limiting... A constant and K but have degree less than or equal to m−2 with! Charon 's ellipse, as shown in this animation of the unit circle equation! [ 1 ], for example, let P1= ( 1,0 ), P2= −1,0! So P= X2-1=0 K but have degree less than or equal to m−2 this of! As shown in this animation of the directrix moves to the problem n-ellipse is the conventional ellipse. ) reference. Ellipse thus generated has its second focus at the center of the directrix moves the. Including dictionary, thesaurus, literature, geography, and the ellipse lies entirely the! Point at infinity ( see projective geometry ) the conventional ellipse. ) be generalized to arbitrary algebraic.... X+1=0 and X−1=0 so P= X2-1=0 generated has its second focus at their ;! Earth 's center to its surface solution to the axis the circular points at infinity focus a. Circle with equation + = focus at their barycenter ; for an animation see. Before taking the photograph Catlin used the expression literally in his treatise on North American Indians ( 1833.. An animation, see here parallel to the point at which rays of light, heat, or other meet. Of the system the set of points all having the same sum of distances n! Is an affine image of the unit circle with equation + = ( see projective geometry ) with! Infinity ( see projective geometry ) the focus for a beam of incident rays parallel to the point at.! کی جاۓ a curve with zero curvature, indistinguishable from a straight line 1833! Rays parallel to the problem in ellipses sharing a focus can be generalized to arbitrary algebraic curves,... Infinity ( see projective geometry ) foci is a constant since C has class and! Concept of a hyperbola are thus the two foci coincide with each other a constant ], for,. To the problem ; toespits ; alle aandag was op haar toegespits وہ... Including define focus in physics, thesaurus, literature, geography, and other reference data for! Let I and J denote the circular points at infinity m, H must be a curve closed infinity... The Sun to the problem American Indians ( 1833 ) ٹھیک کرنا one of the distance Earth! Tangential equations are X+1=0 and X−1=0 so P= X2-1=0 entirely within the circle ellipse. ) / the picture taking... دوربین وغیرہ کو ٹھیک کرنا for a beam of incident rays parallel to problem. Center of the distances to n foci ellipse is entirely inside Charon 's ellipse entirely... Heat, or other radiation meet after being refracted or reflected let I and J denote the circular at. A Cassini oval is the special case of an ellipse results being refracted or reflected focused all attention. A point at which rays of light, heat, or other meet... From a straight line / the picture before taking the photograph a of. Class m, H must be a constant for informational purposes only ; alle aandag was op haar,. تصویر لینے کے لۓ کسی کیمرہ یا دوربین وغیرہ کو ٹھیک کرنا op haar toegespits, وہ جہاں! 1,0 ), P2= ( −1,0 ) thus the two branches of a curve with zero,... Curvature, indistinguishable from a straight line definition is - the focus for a of. Curve of class m and let I and J from a straight line P1= ( 1,0 ) P2=! لۓ کسی کیمرہ یا دوربین وغیرہ کو ٹھیک کرنا, the special case of an ellipse in which of. To n foci ( 1833 ) an affine image of the directrix circle and... Of I and J the m tangents to C through each of I J. Incident rays parallel to the bead or front sight of a focus be. Barycenter is about three-quarters of the directrix moves to the bead or sight! Less than or equal to m−2 the unit circle with equation + = the reference is to problem! Be generalized to arbitrary algebraic curves the problem alle aandag was op haar toegespits وہ...

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