1, be an object, not near to AB as in the figure, but so far off that the bounding lines from A and B would meet at the point corresponding to the point P.Then if a large convex glass AB (called an _object-glass_) be interposed between the object and the eye, all those rays which, proceeding from P, fall on AB, will be caused to converge nearly to a point _p_.

The same is true for every point of the object EMF, and thus a small image, _emf_, will be formed.

This image will not lie exactly on a flat surface, but will be curved about the point midway between A and B as a centre.

Now if the lens AB is removed, and an eye is placed at _m_ to view the distant object EMF, those rays only from each point of the object which fall on the pupil of the eye (whose diameter is about equal to _mp_ suppose) will serve to render the object visible.

On the other hand, every point of the image _emf_ has received the whole of the light gathered up by the large glass AB.