either of two points on the axis of a lens or other optical system, determined by extending an incident oblique ray and the corresponding refracted ray to the axis for the pair of rays that are parallel outside the optical system.
nodal point n.
One of the two points in a compound optical system, located so that a light ray directed through the first point will leave the system through the second point, parallel to its original direction. Also called axial point.
- Nodal rhythm
nodal rhythm n. See atrioventricular nodal rhythm.
- Nodal switching system
(NSS) Main routing nodes in the NSFnet backbone.
National Oceanographic Data Center
Noddack (nŏd’āk’) German chemist who with her husband, Walter Karl Friedrich Noddack (1893-1960), discovered rhenium and an element they called masurium (later named technetium) in 1925.