non-principal axis (NPA) rotational motion
jonbeš-e carxeši be gerd-e âse-ye nâ-farin
Fr.: mouvement rotationnel autour de l'axe non-parincipal
First or highest in rank, importance, value, etc. See also → main.
M.E., from O.Fr. principal, from L. principalis "first in importance," from princeps "first, chief, prince," literally "that takes first," from primus "first" + root of capere "to take."
Farin literally "foremost," from far-, Mid.Pers. fra-; O.Pers. fra- "forward, forth;" Av. frā "forth," pouruua- "first;" cf. Skt. pūrva- "first," pra- "before, formerly;" Gk. pro; L. pro; O.E. fyrst "foremost," superlative of fore, E. fore + -in superlative suffix.
âse-ye farin (#)
Fr.: axe principal
Any imaginary line passing through the center of curvature of a
→ spherical mirror
or → lens and the corresponding geometrical center.
Principal axis is perpendicular
to the mirror or lens at the pole.
Rays of light parallel to the principal axis of a
→ concave mirror
will appear to converge on a point in front of the mirror somewhere
between the mirror's pole and its center of curvature.
Same as → optical axis.
principal quantum number
adad-e kuântomi-ye farin
Fr.: nombre quantique principal
In atomic physics, the first of a set of quantum numbers which describe an atomic orbital. Symbolized as n, it characterizes the size and energy of an orbital.