In optics, the focus is a point in which any number of rays of light meet after being reflected or refracted by a mirror or a lens.
In geometry, the focus is an important point on the principal axis of the parabola, ellipse, and hyperbola. The ellipse and hyperbola have each two foci, the parabola one, though in the latter case we may suppose a second focus at an infinite distance. The foci were so called from the fact that rays of light proceeding from one focus and reflected from a corresponding reflecting surf ace pass through the other focus. Research Focus
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SciTech
Research Focus