Visual Disorders
 Fred |
 Lilly |
"Well, in my opinion this can't be right.
If this was a normal eyeball, then there would be a clear image on the retina. But if you take a closer look at the drawing you can see that there is only a very blurred image on the retina. If the retina would be further to the right, it would exactly be where the focal point of the lens is. Only then a clear image would be projected on the retina. This means that this eyeball is too long and this is called shortsightedness.
It cannot be farsightedness, because then that eyeball would be too short and the clear image would be created behind the retina. As you can see, this isn't what I've drawn."
If this was a normal eyeball, then there would be a clear image on the retina. But if you take a closer look at the drawing you can see that there is only a very blurred image on the retina. If the retina would be further to the right, it would exactly be where the focal point of the lens is. Only then a clear image would be projected on the retina. This means that this eyeball is too long and this is called shortsightedness.
It cannot be farsightedness, because then that eyeball would be too short and the clear image would be created behind the retina. As you can see, this isn't what I've drawn."
"By the way, both shortsightedness and farsightedness can be compensated by lenses. If you add a frame to a pair of lenses you will get glasses and if you have lenses made of very thin plastic foil they are called contact lenses."
Now you surely have an idea how to solve the brain teaser's question from the beginning!
