Part Two - How does the eye work?
and
So you think you need glasses?

Introduction

You are about to partake in the second part of your visionquest. You are going to examine the optics of the human eye. You will learn more about how the eye focuses. And how it captures images. And how you might need eyeglasses to correct your vision.

Task

You will use the internet to research how the optics of the human eye works. You will also find a simple way to demonstrate the optics of the eye that is appropriate for sharing with an elementary age child. You will also be examining how eyeglasses can correct a person's vision.

• How the lens of the eye focuses?
• What are the major eye problems?
• How do different types of lenses help make corrections?
• Finding a simple activity to demonstrate some facet of eye optics to elementary students.
• How to use the lens equation to calculate f.
• What is the cause of the blind spot?
                               

Resources

Internet availability

Process

Read the following sites and research optics of the human eye.

• Optics of the Eye 
• Ophthalmic Hyperguide
• The Human Eye
• How Corrective Lenses Work
• Human Eye Optics

Evaluation

1. You will write a short research paper on how the optics of the eye works. 600-800 words and at least two diagrams. Focus on the lens' ability to change f.
2. You will include one demonstration appropriate for elementary students to show how the eye functions.
3. You will create three ray diagrams showing how a 'normal, eye works and how each type of lens can help correct vision.
4. Calculate the range of focal lengths that your individual eye can achieve.

Conclusion

The optics of the human eye is something many of us take for granted.  They eye's ability to change shape is the key. In our lens labs, we adjusted the image distance to bring an object into focus. This is not possible with the eye, so the eye changes the focal length. Mathematically, it works the same as  normal lens problem except f changes. You can calculate f by using the average image distance of a human eye (about17 mm) and the object upon which you focus.

As with all quests, there is a reward. The reward is in Part Three

Part Three