The Eye

There is a lot to grasp with lenses and between ray diagrams and sign conventions the topic is quite challenging. Let’s reinforce what we learned in the last lesson by applying this material to our eye and corrective lenses like glasses.

Eye Structure

Technically speaking our eye is actually a series of lenses since the cornea bends light in addition to the lens’ refractive abilities. However, we are going to treat our eye as a single lens system for the sake of simplicity.

We have already seen that the lens in our eye acts as a converging lens that can bend light and align the image with the back of our retina. Unfortunately, our lens isn’t always the right shape or our eye is too long or too short.

When our eye is too short it is said that we have myopia or short-sightedness. This means that we can see what is right in front of us, but objects further away will be blurry. If we think of this as a lens problem rather than an eyeball size issue we can see that our lens doesn’t bend light enough.

This means that in order to fix the issue the light needs to come in pre-bent slightly. Therefore, if we placed a converging lens in front of our eye we can bend the light prior to it hitting our lens and have it properly focused on the back of our eye.