Details of how we see and percieve objects and images I am a high school student and I have a question related to the concept of object and image I know  where incident rays intersects this point is called object but here if this is the case

here what will the observer see? for sure light says are entering into his eyes and are also converging at a single point on his retina and sending signals to the brain but what output the brain will give? how will it decide from where these are originating from?
 A: 
how will it (the brain) decide from where these are originating from?

The brain doesn’t have to “decide” anything. Light rays from different points on the object will be brought to a focus at different points of the image (the diagram shows the paths of just two light rays which originate from the same point). In normal vision the lens of the eye can make this image lie on the retina. The muscles of the eye can make small changes to the shape of the lens to bring the image into focus on the retina (and specifically around the fovea, which is the most important part of the retina for detailed vision). This adjustment of the lens is called accommodation
With short sight or long sight the image may be brought into focus in front of or behind the retina, and the eye needs some help to bring the image into focus on the retina. This is what external lenses in spectacles do. External lenses may also be used to make images larger than they would normally be so that the brain can see more detail in the image - this is how magnifying glasses, binoculars, microscopes and telescopes work.
But in any case, all the brain perceives is an image on the retina. The brain does not need to “decide” how far away the object is (although there are ways it can do this if you are using both eyes, or if you move your viewpoint) and does not know anything about any lenses between the eye and the object.
Obviously the brain can tell something about the shape and direction of the source object from its image (although optical illusions exploit the ambiguities in this process). But if the brain could tell the distance and size of the source object from a single image then pictures, computer screens and televisions could not fool the brain into perceiving a three dimensional scene instead of a patchwork of colours on a flat surface. And moving your viewpoint around only helps you determine the relative distance of two objects, not their absolute distance. To determine absolute distance you would need to use some sort of active imaging system such as sonar.
A: to know the distance of an object who picture is on the retina you need two eyes. depending of the distance of the eyes there is a difference between the two pictures and the brain "calculates the distance. Try to meet the points of your finger looking with only one ey, and the will only meet if you adjust more and more, so you have to do it fast, than try the same with to eyes open. If you ever have seen a 3d picture or film with special glasses they project two different pictures to your eyes. With one ey you estimate distance since you know their actual size.
in the actual picture you postet, the ey can not see the point A, since the real picture is at point C, so your ey is not able to see A as a point.
take any  convex lens you own, first decide its focal length, by projecting a picture of a far away thing, best through your window. the sharp picture will be at about the focal distance. Next look at some letters in about 1.3 to 1.5 of the focal length, and your ey closer than 1.5f, you can not see the letters sharp.
A: The observer at O will see a highly defocused image, and their eye lens will not be able to accomodate to get the image into focus.
Let's assume the viewer has normal vision, and is not severely nearsighted or farsighted. For that viewer, objects at infinity are focused at the retina, and form an image image there.     Now consider near objects: Objects closer (say at the end of your arm) would focus beyond the retina, but the eye lens (if working properly) accomodates (which causes an increase in power) and the image moves from beyond the retina to the retina. So the near objects (as long as they are not too close) are in focus.
But the way you have drawn the setup, the light from the first lens is converging. This light will focus in front of the retina. The eye lens will not be able to accomodate in the negative direction. The image in front of the retina will appear out of focus on the retina.
All of this can be changed if someone is severely nearsighted or farsighted, but that's a different problem. If someone were farsighted, it is possible that converging light enters their eye (as you have shown) and that would form a sharp image. Of course, the details matter of how farsighted they are, etc...
A: I remember having the same question at school.  The problem is, all the diagrams given in textbooks have objects at infinity/on the axis.  In reality, the light coming from the top and bottom of the object make slightly different angles with the lens and are focussed at different points
