Which is the light sensitive layer of the eyeball? Where exactly is the image formed on this layer?
Topic: Retina and the yellow spot
Answer
The light-sensitive layer is the RETINA.
The image is formed exactly on the YELLOW SPOT (macula lutea), and most sharply at its centre, the FOVEA CENTRALIS.
One mark for the layer and one for the exact point on it. Note the word EXACTLY — answering only "on the retina" repeats the first half and earns nothing for the second.
WHY THE FOVEA: it is packed almost entirely with CONES and has no overlying nerve fibres, so it gives the sharpest and most detailed colour vision. The eye automatically turns so that whatever you are looking at falls precisely there.
CONTRAST IT with the BLIND SPOT, where the optic nerve leaves the eyeball. That point has NO rods or cones at all, so no image can be formed on it — a favourite examination pairing.