Question

why are rays coming from infinity parallel .. like in the image part(b)..
but the rays coming from the object before infinity ..like in part (a) are diverging ?? why aren't they parallel or why are the parallel rays from infinity not diverging..??

Answer 1

The limit of our eyes to see the far objects is infinity. It means that you can view an object at a distance of infinity kilometers, only you have to magnify them. Sometimes the distance is so much that the angle formed between the radiation coming from O and the principle axis becomes very less, like about 0.1° or 0.2°. This radiation seem to be parallel to the principle axis therefore rays from infinity are drawn parallel.