Final answer:
For an optimal visual image to be generated, the focal point must fall on the retina. Accommodation allows the eye's focal length to adjust, ensuring the image distance equals the lens-to-retina distance for a clear image.
Step-by-step explanation:
To generate an optimal visual image, the focal point must fall on the retina. When light enters the eye, it is refracted by the cornea and the lens to converge at the focal point and form a clear image. If the object is placed at the first focus or the object focus F₁, then the image is formed at infinity, ensuring that when looking at distant objects, they are seen clearly. This process, known as accommodation, involves adjusting the eye's focal length.
To produce clear vision, the image distance dᵢ must equal the lens-to-retina distance, because this does not change with the varying distances of objects observed.
For optimal imaging, it is essential that the focal plane—the plane that contains the focal point—be perfectly aligned with the retina.