How Physics is involved
with the Eye
eye is an example of a case 2
situation (see Lenses), in which the object
is beyond 2F, and the image formed is real, inverted, smaller than
the object, and on the opposite side of the lens. We know that
the image formed must be real, because it is projected onto the
retina (which is like a screen). Any time an image is projected,
it must be real. At the same time, any real image must be inverted.
This might make you wonder why you don’t see objects as being upside
down. Actually, our brain flips things around so that we see them
as being upright.
We know that lenses are needed to focus an object onto a
screen, and in this case the retina. There are different theories
dealing with how the eye focuses its objects. One of these theories
is the 3 lens system. The three lenses would be the aqueous lens,
the lens lens, and the vitreous lens. In this situation, the cornea
would have little refractive power, and just serve as a “cover glass”
to the eye. The aqueous lens lies on top of the pupil, and has
a strong refractive power, because it is a very thick lens. The
lens lens lies right after the pupil. Its index of refraction changes
because there is a density change within the lens itself. The lens
in back of the lens lens is the vitreous lens, which deals a lot
with the magnification of the object.