I want to clear my mind on one basic optics thing:
If I have a point source some distance away from a lens, the position of the image formed can be found using traditional geometrical optics ray approach: one ray passing through the center of the lens and another one parallely to the axis and through the focal point.
If I think about this situation as if the rays are the plane waves: I decompose the light coming from the point source into infinitely many plane waves each reaching the lens at some angle. Now I can draw infinitely many rays for each plane wave which are perpendicular to the plane waves front and all these rays are going through the lens. And I get a lot of different ray directions after the lens, no image is formed. So is there the one exact path during which a ray must be drawn if a plain wave is infinite?
Thank you for clearing this up for me.