focal property

focal property

[′fō·kəl ′präp·ər·dē]
(mathematics)
The property of an ellipse or hyperbola whereby lines drawn from the foci to any point on the conic make equal angles with the tangent to the conic at that point.
The property of a parabola whereby a line from the focus to any point on the parabola, and a line through this point parallel to the axis of the parabola, make equal angles with the tangent to the parabola at this point.
References in periodicals archive ?
The converse of the focal property of the parabola is that light rays which are not parallel to the axis miss the focus.
Sometimes, though not always, criterial vagueness generates vagueness in the focal property under consideration.
Vagueness in constitutive criteria may transmit itself to the focal property itself.