focus : Idioms & Phrases
Index
Aplanatic focus
- of a lens
(Opt.) , the point or focus from which rays diverging pass the lens without spherical aberration. In certain forms of lenses there are two such foci; and it is by taking advantage of this fact that the best aplanatic object glasses of microscopes are constructed.
Webster 1913
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 interchangeable.
Webster 1913
focus on
-
verb center upon
center on; revolve about; revolve around; concentrate on; center.
- Her entire attention centered on her children
- Our day revolved around our work
WordNet
Focus tube
(Phys.) , a vacuum tube for Roentgen rays in which the cathode rays are focused upon the anticathode, for intensifying the effect.
Webster 1913
Principal, ∨ Solar , focus
(Opt.) , the focus for parallel rays.
Webster 1913
Virtual focus
(Opt.) , the point from which rays, having been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it.
Webster 1913
Volcanic foci
- the subterranean centers of volcanic action; the points beneath volcanoes where the causes producing volcanic phenomena are most active.
