It is simply a plane passing thru the focus and perpendicular to the principle axis.
Any parallel beam of light(bundle of light rays) passing thru a lens meets on the focal plane.
In the special case that the beam is parallel to the principle axis, then the rays meet on the focus itself.
Moderation Team
![[Post New]](/templates/default/images/icon_minipost_new.gif){kind=icon}
![[Up]](/templates/default/images/icon_up.gif "[Up]"){kind=icon}
0
